WO2022259044A1 - Fibre-reinforced aerogel composites from mixed silica and rubber sols and a method to produce the rubber-silica aerogel composites - Google Patents
Fibre-reinforced aerogel composites from mixed silica and rubber sols and a method to produce the rubber-silica aerogel composites Download PDFInfo
- Publication number
- WO2022259044A1 WO2022259044A1 PCT/IB2022/050094 IB2022050094W WO2022259044A1 WO 2022259044 A1 WO2022259044 A1 WO 2022259044A1 IB 2022050094 W IB2022050094 W IB 2022050094W WO 2022259044 A1 WO2022259044 A1 WO 2022259044A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- rubber
- fibres
- solution
- silica
- aerogel
- Prior art date
Links
- 239000002131 composite material Substances 0.000 title claims abstract description 122
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 title claims abstract description 109
- 239000004964 aerogel Substances 0.000 title claims abstract description 94
- 229920001971 elastomer Polymers 0.000 title claims abstract description 78
- 239000005060 rubber Substances 0.000 title claims abstract description 78
- 239000000377 silicon dioxide Substances 0.000 title claims abstract description 48
- 238000000034 method Methods 0.000 title claims abstract description 38
- 239000000463 material Substances 0.000 claims abstract description 33
- 239000000243 solution Substances 0.000 claims description 85
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 58
- 239000000203 mixture Substances 0.000 claims description 36
- IJOOHPMOJXWVHK-UHFFFAOYSA-N chlorotrimethylsilane Chemical group C[Si](C)(C)Cl IJOOHPMOJXWVHK-UHFFFAOYSA-N 0.000 claims description 35
- 229920000728 polyester Polymers 0.000 claims description 30
- 239000004965 Silica aerogel Substances 0.000 claims description 25
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 claims description 23
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 21
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 claims description 20
- KFSLWBXXFJQRDL-UHFFFAOYSA-N Peracetic acid Chemical group CC(=O)OO KFSLWBXXFJQRDL-UHFFFAOYSA-N 0.000 claims description 20
- 239000011491 glass wool Substances 0.000 claims description 19
- UQEAIHBTYFGYIE-UHFFFAOYSA-N hexamethyldisiloxane Chemical compound C[Si](C)(C)O[Si](C)(C)C UQEAIHBTYFGYIE-UHFFFAOYSA-N 0.000 claims description 19
- 239000007800 oxidant agent Substances 0.000 claims description 17
- 239000005051 trimethylchlorosilane Substances 0.000 claims description 17
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 17
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 16
- WFDIJRYMOXRFFG-UHFFFAOYSA-N acetic acid anhydride Natural products CC(=O)OC(C)=O WFDIJRYMOXRFFG-UHFFFAOYSA-N 0.000 claims description 16
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 claims description 14
- 229910000077 silane Inorganic materials 0.000 claims description 14
- 239000003054 catalyst Substances 0.000 claims description 13
- 239000003795 chemical substances by application Substances 0.000 claims description 13
- BOTDANWDWHJENH-UHFFFAOYSA-N Tetraethyl orthosilicate Chemical compound CCO[Si](OCC)(OCC)OCC BOTDANWDWHJENH-UHFFFAOYSA-N 0.000 claims description 12
- FFUAGWLWBBFQJT-UHFFFAOYSA-N hexamethyldisilazane Chemical compound C[Si](C)(C)N[Si](C)(C)C FFUAGWLWBBFQJT-UHFFFAOYSA-N 0.000 claims description 12
- BFXIKLCIZHOAAZ-UHFFFAOYSA-N methyltrimethoxysilane Chemical compound CO[Si](C)(OC)OC BFXIKLCIZHOAAZ-UHFFFAOYSA-N 0.000 claims description 12
- BDERNNFJNOPAEC-UHFFFAOYSA-N propan-1-ol Chemical compound CCCO BDERNNFJNOPAEC-UHFFFAOYSA-N 0.000 claims description 10
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 claims description 9
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 9
- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 claims description 9
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 claims description 8
- IMNFDUFMRHMDMM-UHFFFAOYSA-N N-Heptane Chemical compound CCCCCCC IMNFDUFMRHMDMM-UHFFFAOYSA-N 0.000 claims description 8
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 8
- 238000001035 drying Methods 0.000 claims description 7
- WYTZZXDRDKSJID-UHFFFAOYSA-N (3-aminopropyl)triethoxysilane Chemical compound CCO[Si](OCC)(OCC)CCCN WYTZZXDRDKSJID-UHFFFAOYSA-N 0.000 claims description 6
- SJECZPVISLOESU-UHFFFAOYSA-N 3-trimethoxysilylpropan-1-amine Chemical compound CO[Si](OC)(OC)CCCN SJECZPVISLOESU-UHFFFAOYSA-N 0.000 claims description 6
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical group [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 6
- JJQZDUKDJDQPMQ-UHFFFAOYSA-N dimethoxy(dimethyl)silane Chemical compound CO[Si](C)(C)OC JJQZDUKDJDQPMQ-UHFFFAOYSA-N 0.000 claims description 6
- NKSJNEHGWDZZQF-UHFFFAOYSA-N ethenyl(trimethoxy)silane Chemical compound CO[Si](OC)(OC)C=C NKSJNEHGWDZZQF-UHFFFAOYSA-N 0.000 claims description 6
- 238000002156 mixing Methods 0.000 claims description 6
- 238000003756 stirring Methods 0.000 claims description 6
- LFQCEHFDDXELDD-UHFFFAOYSA-N tetramethyl orthosilicate Chemical group CO[Si](OC)(OC)OC LFQCEHFDDXELDD-UHFFFAOYSA-N 0.000 claims description 6
- 230000001476 alcoholic effect Effects 0.000 claims description 5
- 239000012212 insulator Substances 0.000 claims description 5
- 239000002245 particle Substances 0.000 claims description 5
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 4
- 239000000908 ammonium hydroxide Substances 0.000 claims description 4
- 238000010790 dilution Methods 0.000 claims description 4
- 239000012895 dilution Substances 0.000 claims description 4
- 239000012530 fluid Substances 0.000 claims description 4
- 229910017604 nitric acid Inorganic materials 0.000 claims description 4
- 239000012454 non-polar solvent Substances 0.000 claims description 4
- ATRRKUHOCOJYRX-UHFFFAOYSA-N Ammonium bicarbonate Chemical compound [NH4+].OC([O-])=O ATRRKUHOCOJYRX-UHFFFAOYSA-N 0.000 claims description 3
- 239000003463 adsorbent Substances 0.000 claims description 3
- 239000001099 ammonium carbonate Substances 0.000 claims description 3
- 235000012501 ammonium carbonate Nutrition 0.000 claims description 3
- LIKFHECYJZWXFJ-UHFFFAOYSA-N dimethyldichlorosilane Chemical compound C[Si](C)(Cl)Cl LIKFHECYJZWXFJ-UHFFFAOYSA-N 0.000 claims description 3
- 239000003365 glass fiber Substances 0.000 claims description 3
- 239000005055 methyl trichlorosilane Substances 0.000 claims description 3
- JLUFWMXJHAVVNN-UHFFFAOYSA-N methyltrichlorosilane Chemical compound C[Si](Cl)(Cl)Cl JLUFWMXJHAVVNN-UHFFFAOYSA-N 0.000 claims description 3
- TVMXDCGIABBOFY-UHFFFAOYSA-N octane Chemical compound CCCCCCCC TVMXDCGIABBOFY-UHFFFAOYSA-N 0.000 claims description 3
- 150000001282 organosilanes Chemical class 0.000 claims description 3
- 238000005406 washing Methods 0.000 claims description 3
- 239000002904 solvent Substances 0.000 claims description 2
- 239000010920 waste tyre Substances 0.000 abstract description 14
- 239000011159 matrix material Substances 0.000 abstract description 12
- 238000009413 insulation Methods 0.000 abstract description 8
- 238000004064 recycling Methods 0.000 abstract description 6
- 238000001179 sorption measurement Methods 0.000 abstract description 6
- 239000000835 fiber Substances 0.000 description 41
- 235000019441 ethanol Nutrition 0.000 description 30
- 238000002411 thermogravimetry Methods 0.000 description 15
- 230000015556 catabolic process Effects 0.000 description 13
- 238000006731 degradation reaction Methods 0.000 description 13
- 230000004580 weight loss Effects 0.000 description 12
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 description 10
- 238000005452 bending Methods 0.000 description 9
- 230000015572 biosynthetic process Effects 0.000 description 9
- 238000012986 modification Methods 0.000 description 9
- 230000004048 modification Effects 0.000 description 9
- 238000001228 spectrum Methods 0.000 description 9
- 230000003993 interaction Effects 0.000 description 8
- 229920000139 polyethylene terephthalate Polymers 0.000 description 8
- 239000005020 polyethylene terephthalate Substances 0.000 description 8
- 238000012360 testing method Methods 0.000 description 8
- 150000001555 benzenes Chemical group 0.000 description 7
- 238000001157 Fourier transform infrared spectrum Methods 0.000 description 6
- 238000004458 analytical method Methods 0.000 description 6
- 125000003118 aryl group Chemical group 0.000 description 6
- 238000006243 chemical reaction Methods 0.000 description 6
- 239000003921 oil Substances 0.000 description 6
- 238000003786 synthesis reaction Methods 0.000 description 6
- 238000012512 characterization method Methods 0.000 description 5
- 150000001875 compounds Chemical class 0.000 description 5
- 229910052739 hydrogen Inorganic materials 0.000 description 5
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 5
- 239000010410 layer Substances 0.000 description 5
- -1 poly(styrene-butadiene) Polymers 0.000 description 5
- 238000011084 recovery Methods 0.000 description 5
- 238000006722 reduction reaction Methods 0.000 description 5
- 230000002787 reinforcement Effects 0.000 description 5
- 229920002302 Nylon 6,6 Polymers 0.000 description 4
- 239000004952 Polyamide Substances 0.000 description 4
- 229920000297 Rayon Polymers 0.000 description 4
- 150000001408 amides Chemical class 0.000 description 4
- 235000011114 ammonium hydroxide Nutrition 0.000 description 4
- 229910052799 carbon Inorganic materials 0.000 description 4
- 239000006229 carbon black Substances 0.000 description 4
- 230000006835 compression Effects 0.000 description 4
- 238000007906 compression Methods 0.000 description 4
- 125000004185 ester group Chemical group 0.000 description 4
- 239000000499 gel Substances 0.000 description 4
- 239000008187 granular material Substances 0.000 description 4
- 239000001257 hydrogen Substances 0.000 description 4
- 229920002647 polyamide Polymers 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- 239000002964 rayon Substances 0.000 description 4
- 230000009467 reduction Effects 0.000 description 4
- 230000002441 reversible effect Effects 0.000 description 4
- 238000001878 scanning electron micrograph Methods 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- SXRSQZLOMIGNAQ-UHFFFAOYSA-N Glutaraldehyde Chemical compound O=CCCCC=O SXRSQZLOMIGNAQ-UHFFFAOYSA-N 0.000 description 3
- XOJVVFBFDXDTEG-UHFFFAOYSA-N Norphytane Natural products CC(C)CCCC(C)CCCC(C)CCCC(C)C XOJVVFBFDXDTEG-UHFFFAOYSA-N 0.000 description 3
- 239000004372 Polyvinyl alcohol Substances 0.000 description 3
- 238000010521 absorption reaction Methods 0.000 description 3
- 239000002253 acid Substances 0.000 description 3
- 238000004140 cleaning Methods 0.000 description 3
- 239000011248 coating agent Substances 0.000 description 3
- 238000000576 coating method Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000000921 elemental analysis Methods 0.000 description 3
- 238000005187 foaming Methods 0.000 description 3
- 239000011521 glass Substances 0.000 description 3
- 239000000314 lubricant Substances 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 229920002451 polyvinyl alcohol Polymers 0.000 description 3
- 238000002203 pretreatment Methods 0.000 description 3
- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 description 3
- 239000002699 waste material Substances 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 239000004971 Cross linker Substances 0.000 description 2
- 244000043261 Hevea brasiliensis Species 0.000 description 2
- LRHPLDYGYMQRHN-UHFFFAOYSA-N N-Butanol Chemical compound CCCCO LRHPLDYGYMQRHN-UHFFFAOYSA-N 0.000 description 2
- OFBQJSOFQDEBGM-UHFFFAOYSA-N Pentane Chemical compound CCCCC OFBQJSOFQDEBGM-UHFFFAOYSA-N 0.000 description 2
- 229910002808 Si–O–Si Inorganic materials 0.000 description 2
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 2
- 239000005864 Sulphur Substances 0.000 description 2
- 230000002378 acidificating effect Effects 0.000 description 2
- 238000005102 attenuated total reflection Methods 0.000 description 2
- 239000006227 byproduct Substances 0.000 description 2
- 238000012669 compression test Methods 0.000 description 2
- 239000003431 cross linking reagent Substances 0.000 description 2
- 125000004122 cyclic group Chemical group 0.000 description 2
- 230000001066 destructive effect Effects 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 239000010408 film Substances 0.000 description 2
- 239000012467 final product Substances 0.000 description 2
- 238000004108 freeze drying Methods 0.000 description 2
- 229910021389 graphene Inorganic materials 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 230000007062 hydrolysis Effects 0.000 description 2
- 238000006460 hydrolysis reaction Methods 0.000 description 2
- 230000002209 hydrophobic effect Effects 0.000 description 2
- 238000010348 incorporation Methods 0.000 description 2
- 229920000126 latex Polymers 0.000 description 2
- 239000004816 latex Substances 0.000 description 2
- 229920003052 natural elastomer Polymers 0.000 description 2
- 229920001194 natural rubber Polymers 0.000 description 2
- 229920006173 natural rubber latex Polymers 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 125000001997 phenyl group Chemical group [H]C1=C([H])C([H])=C(*)C([H])=C1[H] 0.000 description 2
- 229920006149 polyester-amide block copolymer Polymers 0.000 description 2
- 229920000642 polymer Polymers 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 235000011118 potassium hydroxide Nutrition 0.000 description 2
- 239000002243 precursor Substances 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 238000000197 pyrolysis Methods 0.000 description 2
- 230000009257 reactivity Effects 0.000 description 2
- 239000000741 silica gel Substances 0.000 description 2
- 229910002027 silica gel Inorganic materials 0.000 description 2
- 235000011121 sodium hydroxide Nutrition 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 230000035882 stress Effects 0.000 description 2
- 239000004753 textile Substances 0.000 description 2
- 230000001052 transient effect Effects 0.000 description 2
- 229920001368 Crepe rubber Polymers 0.000 description 1
- XDTMQSROBMDMFD-UHFFFAOYSA-N Cyclohexane Chemical compound C1CCCCC1 XDTMQSROBMDMFD-UHFFFAOYSA-N 0.000 description 1
- 229920002943 EPDM rubber Polymers 0.000 description 1
- 241000272186 Falco columbarius Species 0.000 description 1
- 229920000271 Kevlar® Polymers 0.000 description 1
- 229920002292 Nylon 6 Polymers 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- 239000004793 Polystyrene Substances 0.000 description 1
- 229910008338 Si—(CH3) Inorganic materials 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 239000003377 acid catalyst Substances 0.000 description 1
- 238000013019 agitation Methods 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 239000012298 atmosphere Substances 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 239000012752 auxiliary agent Substances 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 239000003637 basic solution Substances 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 239000011489 building insulation material Substances 0.000 description 1
- 150000001721 carbon Chemical group 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 125000002843 carboxylic acid group Chemical group 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 239000001913 cellulose Substances 0.000 description 1
- 229920002678 cellulose Polymers 0.000 description 1
- PBAYDYUZOSNJGU-UHFFFAOYSA-N chelidonic acid Natural products OC(=O)C1=CC(=O)C=C(C(O)=O)O1 PBAYDYUZOSNJGU-UHFFFAOYSA-N 0.000 description 1
- 239000000701 coagulant Substances 0.000 description 1
- 239000011247 coating layer Substances 0.000 description 1
- 230000000295 complement effect Effects 0.000 description 1
- 239000011246 composite particle Substances 0.000 description 1
- 238000013329 compounding Methods 0.000 description 1
- 230000008602 contraction Effects 0.000 description 1
- 239000007799 cork Substances 0.000 description 1
- 239000007822 coupling agent Substances 0.000 description 1
- 238000004132 cross linking Methods 0.000 description 1
- 238000013016 damping Methods 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 238000000280 densification Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 238000000113 differential scanning calorimetry Methods 0.000 description 1
- 238000007598 dipping method Methods 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 239000012154 double-distilled water Substances 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- 239000000975 dye Substances 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 239000004794 expanded polystyrene Substances 0.000 description 1
- 239000011152 fibreglass Substances 0.000 description 1
- 238000000445 field-emission scanning electron microscopy Methods 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 238000007667 floating Methods 0.000 description 1
- 239000004088 foaming agent Substances 0.000 description 1
- 230000002431 foraging effect Effects 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 239000004761 kevlar Substances 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000003801 milling Methods 0.000 description 1
- 239000011490 mineral wool Substances 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 239000002105 nanoparticle Substances 0.000 description 1
- 239000012299 nitrogen atmosphere Substances 0.000 description 1
- 239000003305 oil spill Substances 0.000 description 1
- 150000002894 organic compounds Chemical class 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 238000005240 physical vapour deposition Methods 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 229920002223 polystyrene Polymers 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000004080 punching Methods 0.000 description 1
- 230000008707 rearrangement Effects 0.000 description 1
- 239000012744 reinforcing agent Substances 0.000 description 1
- 230000003014 reinforcing effect Effects 0.000 description 1
- 239000013557 residual solvent Substances 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 239000010865 sewage Substances 0.000 description 1
- 125000005372 silanol group Chemical group 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 238000006884 silylation reaction Methods 0.000 description 1
- 238000004513 sizing Methods 0.000 description 1
- 239000002594 sorbent Substances 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 229920003048 styrene butadiene rubber Polymers 0.000 description 1
- TXDNPSYEJHXKMK-UHFFFAOYSA-N sulfanylsilane Chemical compound S[SiH3] TXDNPSYEJHXKMK-UHFFFAOYSA-N 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 230000003075 superhydrophobic effect Effects 0.000 description 1
- 229920003051 synthetic elastomer Polymers 0.000 description 1
- 239000005061 synthetic rubber Substances 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 238000002076 thermal analysis method Methods 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 0.000 description 1
- 229920001169 thermoplastic Polymers 0.000 description 1
- 239000004416 thermosoftening plastic Substances 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 239000002966 varnish Substances 0.000 description 1
- 238000004073 vulcanization Methods 0.000 description 1
- 239000004636 vulcanized rubber Substances 0.000 description 1
- 239000002351 wastewater Substances 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J13/00—Colloid chemistry, e.g. the production of colloidal materials or their solutions, not otherwise provided for; Making microcapsules or microballoons
- B01J13/0091—Preparation of aerogels, e.g. xerogels
Definitions
- This application relates to rubber-silica aerogel composites reinforced with fibres and a method to produce said aerogel composites from silica and rubber sols.
- the main component of the tires (70— 80% of the total mass) is vulcanized rubber, and their disposal is an issue, as they are non-biodegradable and cannot be reprocessed in a simple process like the thermoplastics, remaining on the landfills [1], [6], [7].
- the authors were able to obtain rubber aerogels from recycled car tires fibres through the freeze-drying method, using polyvinyl alcohol and glutaraldehyde as crosslinkers.
- the rubber aerogel has densities as low as 35 kg.m -3 , porosities up to 96 %, thermal and sound insulation properties with thermal conductivities between 35 and 47 mW.m _1 .K _1 and a noise reduction coefficient of 0.41.
- the aerogel also has an oil absorption capacity of 19.3 g.g -1 , showing the versatility of the developed material .
- the final product of these works was always a solid rubber [11-16].
- the final product is a stable colloidal rubber solution in alcohol, that can be easily mixed with a silane sol in order to form a rubber-silica solution.
- Evans et al. [17] developed a sulphur-containing organic- inorganic hybrid gel composition and aerogels.
- the authors were also able to obtain a composite from a silica precursor and rubber, however, unlike the present invention, they used a sulphur based cross linking agent to bridge the organic-inorganic components. They also performed a modification of the poly(styrene-butadiene) latex, for example, with a sulfidosilane coupling agent, to increase the organic loading in the final material.
- the developed material is an aerogel-containing high-weather-resistance foaming rubber.
- the synthesis of this material starts with plasticating the ethylene propylene diene monomer rubber and the styrene butadiene rubber, followed by the mixture of these materials to form a sizing material.
- the rubber material is added into a mixer with lubricant, accelerator and an auxiliary agent. After this, the mixture is placed in an open mill; cross-linking, foaming and reinforcing agents were added together with the commercial silica aerogel to obtain the rubber compound. Then, vulcanization, foaming and molding were performed to obtain the foamed sample.
- the third document [20] discloses a thermal insulation sheet comprised of an aerogel layer and a coating layer disposed on both sides of the aerogel layer, where the aerogel layer is formed by binding the aerogel particles with a rubber- based binder.
- Silica aerogel was also used in document [21]. In this work, the incorporation of the silica aerogel is performed by milling this material with unvulcanized crepe rubber to form a product suitable for conventional purposes such as soling.
- the incorporation of silica aerogel nanoparticles into a natural rubber latex (NRL) matrix was also studied in an article by On et al. [22].
- the authors developed a NRL-silica aerogel film by latex compounding and dry coagulant dipping to form a thin film where silica aerogel acts as filler.
- the addition of silica aerogel enhances the mechanical properties of the NRL-silica aerogel film, with 4 phr (parts per hundred rubber) of silica aerogel giving the optimum tensile, tear strength, and elongation at break.
- Recycled car tire fibres were used to obtain a rubber aerogel by using polyvinyl alcohol (PVA) and glutaraldehyde (GA) as crosslinkers through a cost-effective freeze-drying method, in the works developed by Thai et al. [23-25].
- PVA polyvinyl alcohol
- GA glutaraldehyde
- the present application relates to a fibre-reinforced rubber-silica aerogel composite comprising silica and tire rubber and being reinforced with fibres, wherein the composite comprises from 5 to 25% w/w of rubber, has a bulk density between 100 and 200 kg m 3 , contact angle with water between 120 and 160° and thermal conductivity between 14 and 30 mW.m _1 -K _1 .
- the present application also relates to a method to produce the fibre-reinforced rubber-silica aerogel composite comprising the following steps: dissolving tire rubber in a solution comprising an oxidising agent and stirring to obtain a rubber colloidal solution, wherein the tire rubber is present in an amount from 1 to 10% w/v in the rubber colloidal solution;
- the tire rubber is used with a particle diameter lower than 1 mm.
- an alcohol in further added to the rubber and oxidising agent solution is selected from methanol, ethanol, n-propanol, isopropanol, or mixtures thereof.
- the oxidizing agent is selected from peracetic acid, hydrogen peroxide, sulfuric acid, and nitric acid, a mixture of acetic acid or acetic anhydride and hydrogen peroxide, and is present in a concentration varying from 2% to 40% v/v of the rubber colloidal solution.
- the molar ratio between silane and alcohol in the solution varies from 1:5 to 1:35.
- silane is selected from tetramethylorthosilicate (TMOS), tetraethylorthosilicate (TEOS), methyltrimethoxysilane (MTMS), 3- aminopropyltrimethoxysilane (APTMS), aminopropyltriethoxysilane (APTES), vinyltrimethoxysilane (VTMS), or mixtures thereof.
- TMOS tetramethylorthosilicate
- TEOS tetraethylorthosilicate
- MTMS methyltrimethoxysilane
- APITMS aminopropyltrimethoxysilane
- APTES aminopropyltriethoxysilane
- VTMS vinyltrimethoxysilane
- the aqueous basic catalyst is selected from ammonium hydroxide, sodium hydroxide, potassium hydroxide, ammonium carbonate, and the concentration in the aqueous basic catalyst solution varies from 1 mol.L -1 to 15 mol.L -1 .
- the fibres are used in their loose form or in the form of a blanket/mat/felt.
- the solvent of the silylating solution is selected from hexane, heptane, octane, ethanol or isopropanol .
- the first modifying agent is selected from, hexamethyldisiloxane (HMDSO), hexamethyldisilazane (HMDZ), methyltrimethoxysilane (MTMS), dimethoxydimethylsilane (DMDMS), among other organosilanes with non-hydrolysable methyl groups, and is present in the silylating solution in a concentration between 15% and 35% v/v.
- the second modifying agent is selected from trimethylchlorosilane , dimethyldichlorosilane or methyltrichlorosilane, and is present in the silylating solution in a concentration from 5% to 25% v/v.
- the fibres are selected from recycled tire fibres, glass fibres, glass wool, silica fibres, polyester fibres, or other type of organic or inorganic fibres, in the form of loose fibres or a blanket/mat/felt.
- the fibres are pre-treated with an alcoholic solution comprising an oxidising agent, stirred from 1 to 24 hours, filtered, washed and dried.
- the fibre-reinforced rubber-silica aerogel composite is used as a thermal insulator, an acoustic insulator, or as an adsorbent material.
- the goal of the present application is to disclose fibre-reinforced silica/rubber aerogel composites.
- the fibres imbedded in the aerogel matrix ensure its integrity while handling and improves the flexibility of the composite, as silica aerogels are inherently brittle and cannot be bent.
- the final aerogel composite materials herein disclosed were characterized regarding their chemical, physical, structural, and thermal/acoustic properties. Due to their very low thermal conductivity and bulk density, high vibration dissipation, hydrophobicity and good mechanical flexibility, these composite aerogels not only promote the recycling of waste tire, but also have a high potential for thermal and acoustic insulation applications (buildings, roads, automotive, aeronautics/aerospace, among others), as well as an adsorbent material for cleaning wastewaters with apolar pollutants (oils, organic solvents, pharmaceuticals, dyes, among others) by their sorption.
- apolar pollutants oil, organic solvents, pharmaceuticals, dyes, among others
- Figure 1 shows macro-photographs of a) the aerogel composite material with recycled tire fibres, b) the aerogel composite material with polyester fibre blanket, c) the aerogel composite material with silica fibre blanket and d) the aerogel composite material with glass wool.
- Figure 2 shows a) FTIR spectrum and b) TGA of recycled tire fibre.
- Figure 3 shows a) FTIR spectrum and b) TGA of polyester fibre.
- Figure 4 shows a) FTIR spectrum and b) TGA of silica fibre.
- Figure 5 shows a) FTIR spectrum and b) TGA of glass wool.
- Figure 6 shows the reactions of hexamethyldisiloxane (HMDSO) and trimethylchlorosilane (TMCS) with silica surface (1) and reaction of HMDSO with HC1 forming TMCS (2).
- HMDSO hexamethyldisiloxane
- TMCS trimethylchlorosilane
- FIG 7 shows thermogravimetric analysis (TGA) of a) aerogel composite material with recycled tire fibres, b) aerogel composite material with polyester fibre blanket, c) aerogel composite material with silica fibre blanket and d) aerogel composite material with glass wool.
- Figure 8 shows SEM images of a,b) aerogel composite with recycled tire fibres, and c,d) aerogel composite with polyester fibre blanket, e,f) aerogel composite with silica fibre blanket, g,h) aerogel composite with glass wool.
- Figure 9 shows mechanical tests of the aerogel composite material with different fibres, a) Reversible compressive stress-strain curves of the composites until 10% strain; b) ten cycles of reversible compressive stress-strain curves of the composites until 10% strain with a load cell of 50 N; c) reversible compressive stress-strain curves of the composites until 25% strain; and d) uniaxial compression with a load cell of 3 kN.
- the present application relates to fibre-reinforced rubber- silica aerogel composites and a method to produce said aerogel composites.
- the aerogel composites of the present application have a silica/rubber composition and are reinforced with fibres as shown in Figure 1.
- the aerogel composites were produced from rubber sols incorporated in silica sols, and the addition of fibres.
- the method to produce the fibre-reinforced rubber-silica aerogel composite of the present application comprises the following steps:
- the tire rubber is used with a particle diameter of less than 1 mm.
- the rubber is present in an amount from 1 to 10% w/v in the rubber colloidal solution and 5 to 25% w/w of the aerogel composite. In a preferred embodiment, the rubber is 5% w/v of the rubber colloidal solution and 10% w/w of the composite.
- alcohol is added to the solution comprising tire rubber and the oxidising agent.
- the alcohol is selected from, but not limited to, methanol, ethanol, n-propanol, isopropanol, or mixtures thereof.
- the oxidizing agent is selected from, but not limited to, peracetic acid, hydrogen peroxide, sulfuric acid, and nitric acid, a mixture of acetic acid or acetic anhydride and hydrogen peroxide.
- the oxidizing agent concentration varies from 2% to 40% v/v in the rubber colloidal solution.
- the concentration of peracetic acid is 5% v/v.
- the stirring occurs from 1 to 30 hours. In a preferred embodiment, for a concentration of 5% v/v of oxidising agent in the rubber colloidal solution, the stirring time is 24 hours.
- the colloidal solution is 23.5% v/v of the resultant solution.
- the molar ratio between silane and alcohol in the resultant solution varies from 1:5 to 1:35. In a preferred embodiment, the silane:alcohol molar ratio is
- the molar ratio between silane and water in the resultant solution varies from 1:2 to 1:10. In a preferred embodiment, the silane:water molar ratio is 1:4.
- the silane is selected from, but not limited to, tetramethylorthosilicate (TMOS), tetraethylorthosilicate (TEOS), methyltrimethoxysilane (MTMS), 3-aminopropyltrimethoxysilane (APTMS), aminopropyltriethoxysilane (APTES), vinyltrimethoxysilane (VTMS), or mixtures thereof.
- TMOS tetramethylorthosilicate
- TEOS tetraethylorthosilicate
- MTMS methyltrimethoxysilane
- APITMS 3-aminopropyltrimethoxysilane
- APTES aminopropyltriethoxysilane
- VTMS vinyltrimethoxysilane
- the alcohol is selected from, but not limited to, methanol, ethanol, n-propanol, isopropanol, or mixtures thereof. In one embodiment, the mixture is stirred from 5 minutes to 24 hours.
- the method can further comprise a storing step of the previous mixture, but it is not mandatory.
- the mixture can be stored at a temperature between 20°C to 50°C for a period from 1 to 24 hours.
- the molar ratio between silane and water with the basic catalyst solution is from 1:2 to 1:8, but in a preferred embodiment this ratio is 1:4.
- the mixture is under stirring from 1 to 10 minutes.
- the concentration of the base in the aqueous basic catalyst varies from 1 mol.L -1 to 15 mol.L -1 .
- the aqueous basic catalyst is selected from, but not limited to, ammonium hydroxide, sodium hydroxide, potassium hydroxide, ammonium carbonate, among other basic catalysts.
- the volume of the mold is filled with the fibres in their loose form or in the form of a blanket/mat/felt .
- the washing step is performed at a temperature between 15°C and 60°C.
- the alcohol solution is selected from, but not limited to, methanol, ethanol, n-propanol, isopropanol, or their mixtures, and used in an amount of 50 to 95% v/v.
- the non-polar solvent is selected from, but not limited to, pentane, hexane, heptane, cyclohexane, or their mixtures, and used in an amount of 50 to 95% v/v.
- the dilution fluid is selected from hexane, heptane, octane, ethanol or isopropanol, in a concentration between 65% and 85% v/v in the silylating solution.
- the first modifying agent is present in the silylating solution in a concentration between 15% and 35% v/v.
- the first modifying agent is selected from, but not limited to, hexamethyldisiloxane (HMDSO), hexamethyldisilazane (HMDZ), methyltrimethoxysilane (MTMS), dimethoxydimethylsilane (DMDMS), among other organosilanes with non-hydrolysable methyl groups.
- HMDSO hexamethyldisiloxane
- HMDZ hexamethyldisilazane
- MTMS methyltrimethoxysilane
- DDMS dimethoxydimethylsilane
- the second modifying agent is selected from TMCS, dimethyldichlorosilane or methyltrichlorosilane, but preferentially TMCS, and is present in the silylating solution in a concentration from 5% to 25% v/v.
- the silylating solution is stirred for a time between 5 and 60 minutes.
- the composite aerogel is incubated in the silylating solution at a temperature between 15 °C and 60 °C, for a time between 24 h and 96 hours.
- the composite aerogel is dried temperatures between 50 °C and 200 °C, depending on the thermal stability of the reinforcing fibres.
- the fibres for composite reinforcement are selected from recycled tire fibres, glass fibres, glass wool, silica fibres, polyester fibres, or other type of organic or inorganic fibres.
- the fibres are used either in the form of a blanket/ /mat/felt or used as loose fibres dispersed layer-by-layer in the mold.
- a fibre blanket is understood as a non-woven fibre network (for example like a felt), with the fibres randomly distributed or aligned in horizontal/longitudinal direction.
- recycled tire fibres these can be assembled in a mat by needle-punching them before insertion in the mold.
- recycled tire fibres are used for reinforcement, they can be used in their pristine state or after being modified by an acid solution pre-treatment.
- the fibre pre-treatment step is achieved by mixing the tire fibres with an alcoholic solution comprising an oxidising agent. This mixture is stirred from 1 to 24 hours and then filtered. The fibres are then washed with alcohol, for example using the centrifuge, and then dried at a temperature between 40 °C and 250 °C.
- the alcohol of this step is selected from, but not limited to, ethanol, methanol, isopropanol or butanol.
- the oxidizing agent of this step is selected from, but not limited to, peracetic acid, hydrogen peroxide, a mixture of acetic acid or acetic anhydride and hydrogen peroxide, sulfuric acid, and nitric acid, and is present in the pre-treatment alcoholic solution in a concentration 2 to 40% v/v.
- the alcohol to wash the fibres is selected from, but not limited to, methanol, ethanol, or isopropanol or mixtures thereof, used in a concentration varying from 50 to 95% v/v.
- the fibre-reinforced rubber-silica aerogel composite disclosed in the present application is made from the mixing of silica and rubber sols, comprising from 5 to 25% w/w of rubber in the composite. It has negligible shrinkage, bulk density between 100 and 200 kg m 3 , contact angle with water between 120 and 160°, thermal conductivity between 14 and 30 mW.m _1 -K _1 , and with negligible weight loss up to 400 °C in the case of the more thermally stable fibres and inert atmosphere .
- Tire rubber (diameter ⁇ 0.8 mm), ethanol (absolute, Fluka; C2H5OH), peracetic acid (38-40%, Merck; CH3CO3H), tetraethylorthosilicate (TEOS; purity 3 99%, Aldrich; Si (OC2H5)4), ammonium hydroxide (25% NH3 in H2O, Fluka Analytical; NH4OH), n-hexane (C6H14, purity > 95%, Fisher Chemical), hexamethyldisiloxane (HMDSO, (CH3)3SiOSi(CH3)3, purity > 98%, Acros Organics), trimethylchlorosilane (TMCS, (CH3)3SiCl, purity 3 98%, Sigma Aldrich) and several types of fibres were used in the composites production.
- TMCS trimethylchlorosilane
- the fibres acted as reinforcement of composites.
- the tire fibres include the following three main components: i) natural rubber and synthetic rubber polymers, ii) steel wire and iii) textile fibres (Nylon 6 and 66, Polyester, Kevlar, Rayon and Glass). A polyester fibre blanket, a silica fibre felt, and glass wool were also applied as alternatives to tire fibres. 1 . Aerogel composite synthesis
- the first step for the composite synthesis 0.5 g of tire rubber was dissolved in a 10 mL solution containing ethanol and peracetic acid, with acid concentration of 5.0 vol.%. The solution was stirred for 24 h. After this period, a black colloidal solution was obtained. In one embodiment, the concentration of peracetic acid solution was 5 vol.% with a dissolution time of 24 h.
- the rubber colloidal solution was mixed with the silica sol. So, ethanol, TEOS and double distilled water were added, with a molar ratio of 10:1:4, to the rubber colloidal solution, and the mixture was stirred for 30 min. This solution was then stored in an oven at 27 °C for 24 h for the hydrolysis step. A basic solution, NH 4 OH 2.5 M, was added to the former solution and kept under strong agitation for 1 minute and then poured into the mold with the fibre blanket. The samples were kept in the oven at 27 °C during 5 days for aging.
- the composite aerogels were unmolded and washed with ethanol and hexane at 50 °C.
- the aerogel samples were then subjected to a surface modification.
- the silylating solution comprises hexane, HMDSO and TMCS (70:20:10 volumetric percentages).
- hexane and HMDSO were added to the aerogel samples, and the solution was stirred for 30 min, and then TMCS was added, and the solution is stirred for another 30 min.
- the aerogel samples were immersed in the silylating solution and then placed in an oven at 50 °C and kept at that temperature for 8 h. After that, the samples are kept in the silylating solution for another 48 hours at a temperature between 15 and 35 °C. To dry the samples, the solution was removed, and the samples are kept in a hood for 24 h and then subjected to 100 °C for 3 h and 150 °C for 3 h.
- the properties of the final composite aerogel materials were assessed by different characterization techniques.
- the bulk density (p b ) was calculated from the weight and volume of regular pieces of the samples.
- the chemical structure was evaluated by attenuated total reflection (ATR) Fourier- transform infrared spectroscopy (FTIR) (FT/IR 4200, Jasco), collecting the spectra between a wavenumber of 4000 and 400 cm -1 , with 128 scans and 4 cm -1 of resolution.
- ATR attenuated total reflection
- FTIR Fourier- transform infrared spectroscopy
- EA elemental analysis
- SEM images were obtained using a Compact/VPCompact FESEM (Zeiss Merlin) microscope, after coating the aerogel samples with a thin gold layer by Physical Vapor Deposition, during 20 s.
- Thermal properties were assessed by thermal gravimetric analysis and thermal conductivity.
- the thermal stability of different materials was obtained by using a DSC/TGA equipment (TGA-Q500, TA Instruments), from 20 °C to 800 °C, at a 10 °C.min _1 heating rate under nitrogen flow.
- Thermal conductivity, k was measured with a Thermal Constants Analyzer TPS 2500 S (Hot Disk), using the transient plane source method with two samples maintained at 20 °C.
- the dynamic stiffness, s t ' was measured following the test procedures defined in standard ISO 9052-1 and the test-samples have a thickness of 15 mm and an area of 20.0 x 20.0 cm 2 .
- Sorption tests were also performed with the composite reinforced with the polyester fibre blanket.
- the composite was placed floating on water with motor lubricant oil for 10 minutes and the percentage of oil removed from the water by the composite was recorded.
- the test samples have a thickness of 13 mm and an area 3.0 x 1.0 cm 2 and they were turned 180° after 5 minutes of exposure.
- the FTIR results it was possible to confirm the presence of two main types of fibres: (1) a polyester fibre - poly(ethylene terephthalate) (PET) fibre, and (2) a polyamide fibre - nylon 6,6.
- PET poly(ethylene terephthalate)
- the bands associated with the polyester fibres in the FTIR spectra are 1, 3, 5, 9, 11-20, while for the polyamide, the bands are 2, 4, 6-10; 21, 22.
- PET and nylon 6,6 are the most commonly used polymers in tires.
- other fibres such as glass or rayon can also be present in the textile fibre used, but in lower amounts than the ones detected by FTIR analysis.
- the TGA analysis ( Figure 2b) of the recycled tire fibres also indicates a mixture of fibres, as detected in FTIR, as a two-step process was observed.
- the first degradation step consisted in a weight loss of 11.4% with an onset temperature of 324.3 °C
- the second step showed a weight loss of 66 % and onset temperature of 377 °C, with a maximum at 417 °C.
- the thermal degradation between 25-100 °C can be attributed to the loss of water. It is possible that the first degradation step is related to the other fibres present in the mixture, such as rayon fibre, that presents a thermal degradation temperature between 250 °C and 350 °C, while the second step is attributed to the degradation of both polyester and polyamide fibres.
- the thermal conductivity of this fibre mat is 67.50 ⁇ 0.14 mW.m _1 .K _1 (Hot Disk). This result is lower than the one obtained for the rubber (91.09 ⁇ 0.13 mW.m _1 .K _1 ), but still higher than common materials used for thermal insulation, as previously described.
- Polyester fibre blanket was also submitted to FTIR analysis, and the spectrum is presented in Figure 3a.
- the thermal stability of the polyester fibres was investigated using TGA measurement, Figure 3b.
- the TGA data showed an onset temperature of 406 °C, and total weight loss of 77.5%, which is in agreement with the literature data for PET samples.
- the thermal conductivity of the PET was also assessed, with a value of 33.90 ⁇ 0.05 mW.m _1 .K _1 (Hot Disk). This result is much lower than the ones obtained for the rubber and the recycled tire fibres, however, it is still higher than the very low thermal conductivities of silica aerogels, that are typically in the order of 15 mW.m _1 .K _1 , at ambient temperature, pressure and relative humidity.
- the silica fibre felt was also analysed by FTIR, and the spectrum is presented in Figure 4a.
- the spectrum of this inorganic fibre shows different bands that can be attributed to: (1) silanol groups; (2) stretching of aliphatic C-H groups; (3) asymmetric bending of C-H groups; (4) and (5) asymmetric stretching vibration of Si-O-Si groups; and (6) Si-0 symmetric stretching vibration.
- the C-H groups are due to a thin coating of varnish on the top of the fibre felt.
- the thermal degradation of the silica fibres was assessed through thermal gravimetric analysis. As observed in Figure 4b, this fibre only presented one small weight loss (around 3.9%), with an onset temperature of 270 °C, that is attributed to the degradation of the finishing organic coating.
- the silica fibres presented a thermal conductivity of 29.08 ⁇ 0.20 mW.m _1 .K _1 (Hot Disk), the lowest between the fibres used in this work, however, as already mentioned, it is still higher than the values obtained for the silica aerogels.
- Table 1 shows some composites' properties and Figure 1 the macro-photographs of the samples.
- the composites displayed negligible shrinkage during the drying step (Table 1), thus keeping intact the pore structure of the gel, which contributes to the excellent insulation performance and sorption capacity.
- Two main factors contribute to the absence of shrinkage.
- the second factor is related to the modification of the silica matrix. After the modification step, the silica gel has a hydrophobic character (Table 1, see contact angle), which makes possible the "spring-back" effect of the matrix (reversible shrinkage).
- TMCS enhances the reactivity of HMDSO, since the HC1 needed for the cision of the HMDSO is formed during the reaction of TMCS with silica pendant hydroxyl groups.
- the occurring reactions are displayed in Figure 6. As these chain reactions occur, they enhance the surface modification and lead to the formation of an aerogel matrix with uniform structure and low density, as observed in the composites here developed.
- the materials have densities in the same range of other fibre-reinforced silica aerogel composites dried in ambient pressure conditions.
- the density has a high influence in the thermal conductivity of the samples, with most of the relevant superinsulating S1O2 aerogels commercially available having densities between 80 and 200 kg m -3 .
- the pure silica aerogel, TEOS-based matrix with the same modification procedure than the composites has a thermal conductivity of 24.67 ⁇ 0.14 mW.iti -1 .K _1
- the rubber-silica aerogel (addition of rubber into the TEOS sol and modified with HMDSO/TMCS) exhibits a value of 24.82 ⁇ 0.05 mW.m _1 .K _1 , when measuring by Hot Disk transient method.
- the similar values of both aerogels indicate a good interaction between the two phases to form the three-dimensional network, which was later confirmed by SEM images.
- Table 1 Structural and thermal properties and hydrophobicity of the aerogel composites. a Panels with 21.5 x 21.5 cm 2 of area.
- Figure 9d presents the non-linear stress-strain curve, in which the compression progress of the sample contains three stages. At the first stage, with the strain ranging from 0% to around 30%, known as linear stage, the slope of the compression curve remains unchanged, and the open pores act as the main support of the composite. The second stage, the yielding stage (strain in the range of 30% to 60%), the stress increases at a fixed rate and the fibres become the main load-bearing part. In the final part, the densification stage (from 60% to ⁇ 95%), the collapse of the aerogel part and a significant increase in the curve slope are observed.
- the measured dynamic stiffness of the new aerogel composite with polyester fibres was 11 MN.m -3 .
- the measured dynamic stiffness of the new aerogel composite is significantly lower.
Abstract
The present application discloses aerogel composites of rubber and silica that are reinforced with fibres, and a method to produce said aerogel composites. Due to their very low thermal conductivity and bulk density, high vibration dissipation, hydrophobicity and good mechanical flexibility, the aerogel composites of the present application not only promote the recycling of waste tire, which is the source material for the rubber sols, but also have a high potential for thermal and acoustic insulation applications, as well as applications that can benefit from these aerogel composites high sorption capacity. The fibres imbedded in the aerogel composites matrix ensures its integrity while handling and improves the flexibility of the aerogel composites.
Description
DESCRIPTION
"FIBRE-REINFORCED AEROGEL COMPOSITES FROM MIXED SILICA AND RUBBER SOLS AND A METHOD TO PRODUCE THE RUBBER-SILICA
AEROGEL COMPOSITES"
Technical field
This application relates to rubber-silica aerogel composites reinforced with fibres and a method to produce said aerogel composites from silica and rubber sols.
Background art
One of the most critical issues in modern society is the constant increase of waste [1]. Currently, over 1.6 billion new tires and around 1 billion of waste tires are generated worldwide every year [2]. In the last decade, there has been a growth in the number of tires being discarded as end-of- life tires (ELTs) [1], which leads to serious environmental problems. In order to improve the waste management practices, the European legislation has established a priority order for dealing with wastes, from the most preferred option of reduction, followed by reuse, recycling, energy production to least preferred option of disposal [3]-[5]. However, significant difficulties are associated with the recovery and recycling of used tires, due to their composition and complex structure [6]. The main component of the tires (70— 80% of the total mass) is vulcanized rubber, and their disposal is an issue, as they are non-biodegradable and cannot be reprocessed in a simple process like the thermoplastics, remaining on the landfills [1], [6], [7].
To engage in more environmentally friendly solutions, and comply with more restrict legislations, new methods for the
treatment or reuse/recycling of the basic components of ELTs are being developed. Dwivedi and co-authors [8] were able to use the carbon-rich solid (RCB) fraction, from the pyrolysis of waste tires, as a partial substitute to conventional carbon black (CB) in natural rubber-based conveyor belts cover composites. The mechanical properties of the RCB reinforced composites were lower than the material obtained with conventional CB. However, when a combination of RCB and commercial CB were used, these limitations could be overcome, and the impact in the mechanical properties is acceptable. This partial replacement reduces the cost of rubber compounds and provides a sustainable recycling option of waste tires.
Another approach was developed by Passaponti et al. [9], in which the authors were able to recover and valorize the chars, the least valuable by-product of waste tire pyrolysis. They were able to convert this material into highly efficient catalysts for the Oxygen Reduction Reaction (ORR), with a simple heat treatment. The sample prepared at 450°C displayed the maximum catalytic activity, with a conversion efficiency of O2 to H2O above 85%. The developed material has potential to be applied in alkaline fuel cells and metal air batteries.
Wang et al. [10] were able to directly convert waste tires into 3D graphene, by raising pyrolytic temperature to 1000°C and using an active K vapor to induce carbon atom rearrangement. The final material displays a well-defined porous gradient and high electrical conductivity (18.2 S.cm 1). When applied as supercapacitor electrode, the graphene exhibits an excellent capacitive behaviour, with almost no degradation after 10000 cycles. This work provides a new consideration for the development of more high-value products from waste tires.
Another possibility to obtain high value products is the synthesis of aerogels from waste tires, as presented by Thai et al. [7]. The authors were able to obtain rubber aerogels from recycled car tires fibres through the freeze-drying method, using polyvinyl alcohol and glutaraldehyde as crosslinkers. The rubber aerogel has densities as low as 35 kg.m-3, porosities up to 96 %, thermal and sound insulation properties with thermal conductivities between 35 and 47 mW.m_1.K_1 and a noise reduction coefficient of 0.41. Besides that, the aerogel also has an oil absorption capacity of 19.3 g.g-1, showing the versatility of the developed material .
Some works have already treated rubber with peracetic acid for producing epoxidized rubber; however, the final product of these works was always a solid rubber [11-16]. In the present invention, the final product is a stable colloidal rubber solution in alcohol, that can be easily mixed with a silane sol in order to form a rubber-silica solution.
Evans et al. [17] developed a sulphur-containing organic- inorganic hybrid gel composition and aerogels. In this document, the authors were also able to obtain a composite from a silica precursor and rubber, however, unlike the present invention, they used a sulphur based cross linking agent to bridge the organic-inorganic components. They also performed a modification of the poly(styrene-butadiene) latex, for example, with a sulfidosilane coupling agent, to increase the organic loading in the final material.
A few other documents also developed composites with silica aerogel and rubber [18-21], but with very different procedures when compared to the one disclosed in this
application. In the first [18], the authors obtained aerogel- blown rubber composite particles for sewage disposal. For the preparation of this composite, first the authors prepared a silica gel, and, in the sequence a demulsifier was added into the gel. The next step was to add blown rubber particles in the previous mixture, to be then dried using supercritical carbon dioxide.
For the second document [19], the developed material is an aerogel-containing high-weather-resistance foaming rubber. The synthesis of this material starts with plasticating the ethylene propylene diene monomer rubber and the styrene butadiene rubber, followed by the mixture of these materials to form a sizing material. In the next step, the rubber material is added into a mixer with lubricant, accelerator and an auxiliary agent. After this, the mixture is placed in an open mill; cross-linking, foaming and reinforcing agents were added together with the commercial silica aerogel to obtain the rubber compound. Then, vulcanization, foaming and molding were performed to obtain the foamed sample.
The third document [20] discloses a thermal insulation sheet comprised of an aerogel layer and a coating layer disposed on both sides of the aerogel layer, where the aerogel layer is formed by binding the aerogel particles with a rubber- based binder.
Silica aerogel was also used in document [21]. In this work, the incorporation of the silica aerogel is performed by milling this material with unvulcanized crepe rubber to form a product suitable for conventional purposes such as soling.
The incorporation of silica aerogel nanoparticles into a natural rubber latex (NRL) matrix was also studied in an article by On et al. [22]. The authors developed a NRL-silica aerogel film by latex compounding and dry coagulant dipping to form a thin film where silica aerogel acts as filler. The addition of silica aerogel enhances the mechanical properties of the NRL-silica aerogel film, with 4 phr (parts per hundred rubber) of silica aerogel giving the optimum tensile, tear strength, and elongation at break.
Recycled car tire fibres were used to obtain a rubber aerogel by using polyvinyl alcohol (PVA) and glutaraldehyde (GA) as crosslinkers through a cost-effective freeze-drying method, in the works developed by Thai et al. [23-25]. The combination of properties of the aerogels, such as ultra-low density (0.020-0.091 g.cm3), super-hydrophobic properties (water contact angle up to 153°), high sound absorption efficiency (noise reduction coefficient of 0.56) and low thermal conductivity (35 - 49 mW.nr1.K_1), makes them useful to be applied in different areas, for example thermal insulation, sound absorption and oil spill-cleaning applications. It should be noted that this material does not contain silica, it is most likely a crosslinked fibre mat.
Even though the composite materials here cited have similar denominations as the present invention, the synthesis procedures are completely different than the one of the present application.
Summary
The present application relates to a fibre-reinforced rubber-silica aerogel composite comprising silica and tire
rubber and being reinforced with fibres, wherein the composite comprises from 5 to 25% w/w of rubber, has a bulk density between 100 and 200 kg m3, contact angle with water between 120 and 160° and thermal conductivity between 14 and 30 mW.m_1-K_1.
The present application also relates to a method to produce the fibre-reinforced rubber-silica aerogel composite comprising the following steps: dissolving tire rubber in a solution comprising an oxidising agent and stirring to obtain a rubber colloidal solution, wherein the tire rubber is present in an amount from 1 to 10% w/v in the rubber colloidal solution;
- mixing the previous rubber colloidal solution with a solution comprising a silane, an alcohol and water;
- adding an aqueous basic catalyst solution to the previous mixture;
- pouring the previous mixture into a mold comprising fibres to form the aerogel composite;
- unmolding the aerogel composite and washing it first with an alcohol solution and afterwards with a non-polar solvent;
- modifying the surface of the aerogel composite by immersing the aerogel composite in a silylating solution comprising a dilution fluid and a first modifying agent, then adding a second modifying agent to the solution, and incubating the aerogel composite in the solution;
- drying the composite aerogel.
In one embodiment the tire rubber is used with a particle diameter lower than 1 mm.
In another embodiment an alcohol in further added to the rubber and oxidising agent solution and is selected from
methanol, ethanol, n-propanol, isopropanol, or mixtures thereof.
In yet another embodiment the oxidizing agent is selected from peracetic acid, hydrogen peroxide, sulfuric acid, and nitric acid, a mixture of acetic acid or acetic anhydride and hydrogen peroxide, and is present in a concentration varying from 2% to 40% v/v of the rubber colloidal solution.
In one embodiment the molar ratio between silane and alcohol in the solution varies from 1:5 to 1:35.
In another embodiment silane is selected from tetramethylorthosilicate (TMOS), tetraethylorthosilicate (TEOS), methyltrimethoxysilane (MTMS), 3- aminopropyltrimethoxysilane (APTMS), aminopropyltriethoxysilane (APTES), vinyltrimethoxysilane (VTMS), or mixtures thereof.
In yet another embodiment the aqueous basic catalyst is selected from ammonium hydroxide, sodium hydroxide, potassium hydroxide, ammonium carbonate, and the concentration in the aqueous basic catalyst solution varies from 1 mol.L-1 to 15 mol.L-1.
In one embodiment the fibres are used in their loose form or in the form of a blanket/mat/felt.
In another embodiment the solvent of the silylating solution is selected from hexane, heptane, octane, ethanol or isopropanol .
In one embodiment the first modifying agent is selected from, hexamethyldisiloxane (HMDSO), hexamethyldisilazane (HMDZ), methyltrimethoxysilane (MTMS), dimethoxydimethylsilane (DMDMS), among other organosilanes with non-hydrolysable methyl groups, and is present in the silylating solution in a concentration between 15% and 35% v/v.
In one embodiment the second modifying agent is selected from trimethylchlorosilane , dimethyldichlorosilane or methyltrichlorosilane, and is present in the silylating solution in a concentration from 5% to 25% v/v.
In one embodiment the fibres are selected from recycled tire fibres, glass fibres, glass wool, silica fibres, polyester fibres, or other type of organic or inorganic fibres, in the form of loose fibres or a blanket/mat/felt.
In one embodiment the fibres are pre-treated with an alcoholic solution comprising an oxidising agent, stirred from 1 to 24 hours, filtered, washed and dried.
In one embodiment the fibre-reinforced rubber-silica aerogel composite is used as a thermal insulator, an acoustic insulator, or as an adsorbent material.
General description
Motivated by the environmental problems caused by ELTs, and the current potential markets for products obtained with recycled/reused materials, the goal of the present application is to disclose fibre-reinforced silica/rubber aerogel composites. The fibres imbedded in the aerogel matrix ensure its integrity while handling and improves the
flexibility of the composite, as silica aerogels are inherently brittle and cannot be bent.
For the first time, recycled rubber sols were produced and incorporated in the silica sols. Since the ELTs rubber is vulcanized, it is very difficult to link its granules to other compounds in composites. Even when strategies are implemented to cross-link the rubber granules with other organic matrices or organically-modified inorganic matrices, these linkages are normally not strong enough and the granules easily separate from the composite. Therefore, a strategy that transforms rubber granules into a rubber sol, by the use of an acidic strong oxidizer, will allow the intimate mixing of this sol with the silica sol (in the case of the aerogel), avoiding the segregation of the two phases. In addition, the acidic nature of the oxidizer will promote hydrolysis of the silica precursors without the need of using other acid catalysts.
The final aerogel composite materials herein disclosed were characterized regarding their chemical, physical, structural, and thermal/acoustic properties. Due to their very low thermal conductivity and bulk density, high vibration dissipation, hydrophobicity and good mechanical flexibility, these composite aerogels not only promote the recycling of waste tire, but also have a high potential for thermal and acoustic insulation applications (buildings, roads, automotive, aeronautics/aerospace, among others), as well as an adsorbent material for cleaning wastewaters with apolar pollutants (oils, organic solvents, pharmaceuticals, dyes, among others) by their sorption.
Brief description of drawings
For easier understanding of this application, figures are attached in the annex that represent the preferred forms of implementation which nevertheless are not intended to limit the technique disclosed herein.
Figure 1 shows macro-photographs of a) the aerogel composite material with recycled tire fibres, b) the aerogel composite material with polyester fibre blanket, c) the aerogel composite material with silica fibre blanket and d) the aerogel composite material with glass wool.
Figure 2 shows a) FTIR spectrum and b) TGA of recycled tire fibre.
Figure 3 shows a) FTIR spectrum and b) TGA of polyester fibre.
Figure 4 shows a) FTIR spectrum and b) TGA of silica fibre.
Figure 5 shows a) FTIR spectrum and b) TGA of glass wool.
Figure 6 shows the reactions of hexamethyldisiloxane (HMDSO) and trimethylchlorosilane (TMCS) with silica surface (1) and reaction of HMDSO with HC1 forming TMCS (2).
Figure 7 shows thermogravimetric analysis (TGA) of a) aerogel composite material with recycled tire fibres, b) aerogel composite material with polyester fibre blanket, c) aerogel composite material with silica fibre blanket and d) aerogel composite material with glass wool.
Figure 8 shows SEM images of a,b) aerogel composite with recycled tire fibres, and c,d) aerogel composite with polyester fibre blanket, e,f) aerogel composite with silica fibre blanket, g,h) aerogel composite with glass wool. a,c,e,g) Interaction of the silica phase with the fibres; b,d,f,h) rubber and silica matrix..
Figure 9 shows mechanical tests of the aerogel composite material with different fibres, a) Reversible compressive stress-strain curves of the composites until 10% strain; b) ten cycles of reversible compressive stress-strain curves of the composites until 10% strain with a load cell of 50 N; c) reversible compressive stress-strain curves of the composites until 25% strain; and d) uniaxial compression with a load cell of 3 kN.
Description of embodiments
Now, preferred embodiments of the present application will be described in detail with reference to the annexed drawings. However, they are not intended to limit the scope of this application.
The present application relates to fibre-reinforced rubber- silica aerogel composites and a method to produce said aerogel composites.
The aerogel composites of the present application have a silica/rubber composition and are reinforced with fibres as shown in Figure 1.
The aerogel composites were produced from rubber sols incorporated in silica sols, and the addition of fibres.
The method to produce the fibre-reinforced rubber-silica aerogel composite of the present application comprises the following steps:
- Dissolving tire rubber in a solution comprising an oxidising agent, and stirring to obtain a rubber colloidal solution;
In one embodiment, the tire rubber is used with a particle diameter of less than 1 mm.
In one embodiment the rubber is present in an amount from 1 to 10% w/v in the rubber colloidal solution and 5 to 25% w/w of the aerogel composite. In a preferred embodiment, the rubber is 5% w/v of the rubber colloidal solution and 10% w/w of the composite.
In one embodiment alcohol is added to the solution comprising tire rubber and the oxidising agent.
In one embodiment, the alcohol is selected from, but not limited to, methanol, ethanol, n-propanol, isopropanol, or mixtures thereof.
In one embodiment, the oxidizing agent is selected from, but not limited to, peracetic acid, hydrogen peroxide, sulfuric acid, and nitric acid, a mixture of acetic acid or acetic anhydride and hydrogen peroxide.
The oxidizing agent concentration varies from 2% to 40% v/v in the rubber colloidal solution. In a preferred embodiment, the concentration of peracetic acid is 5% v/v.
In one embodiment, the stirring occurs from 1 to 30 hours.
In a preferred embodiment, for a concentration of 5% v/v of oxidising agent in the rubber colloidal solution, the stirring time is 24 hours.
- Mixing the previous rubber colloidal solution with a solution comprising a silane, an alcohol and water; with the rubber colloidal solution being 15 to 30 vol.% of the resultant solution.
In one embodiment the colloidal solution is 23.5% v/v of the resultant solution.
In one embodiment, the molar ratio between silane and alcohol in the resultant solution varies from 1:5 to 1:35. In a preferred embodiment, the silane:alcohol molar ratio is
1:10.
In one embodiment, the molar ratio between silane and water in the resultant solution varies from 1:2 to 1:10. In a preferred embodiment, the silane:water molar ratio is 1:4.
In one embodiment, the silane is selected from, but not limited to, tetramethylorthosilicate (TMOS), tetraethylorthosilicate (TEOS), methyltrimethoxysilane (MTMS), 3-aminopropyltrimethoxysilane (APTMS), aminopropyltriethoxysilane (APTES), vinyltrimethoxysilane (VTMS), or mixtures thereof.
In one embodiment, the alcohol is selected from, but not limited to, methanol, ethanol, n-propanol, isopropanol, or mixtures thereof.
In one embodiment, the mixture is stirred from 5 minutes to 24 hours.
In one embodiment, the method can further comprise a storing step of the previous mixture, but it is not mandatory. The mixture can be stored at a temperature between 20°C to 50°C for a period from 1 to 24 hours.
- Adding an aqueous basic catalyst solution to the previous mixture;
In one embodiment the molar ratio between silane and water with the basic catalyst solution is from 1:2 to 1:8, but in a preferred embodiment this ratio is 1:4.
In one embodiment the mixture is under stirring from 1 to 10 minutes.
In one embodiment the concentration of the base in the aqueous basic catalyst varies from 1 mol.L-1 to 15 mol.L-1.
In one embodiment the aqueous basic catalyst is selected from, but not limited to, ammonium hydroxide, sodium hydroxide, potassium hydroxide, ammonium carbonate, among other basic catalysts.
- Pouring the previous mixture into a mold comprising fibres to form the aerogel composite;
In one embodiment, the volume of the mold is filled with the fibres in their loose form or in the form of a blanket/mat/felt .
- Unmolding the aerogel composite and wash it first with an alcohol solution and afterwards with a non-polar solvent;
In one embodiment, the washing step is performed at a temperature between 15°C and 60°C.
In one embodiment, the alcohol solution is selected from, but not limited to, methanol, ethanol, n-propanol, isopropanol, or their mixtures, and used in an amount of 50 to 95% v/v.
In one embodiment, the non-polar solvent is selected from, but not limited to, pentane, hexane, heptane, cyclohexane, or their mixtures, and used in an amount of 50 to 95% v/v.
- Modifying the surface of the aerogel composite by immersing the aerogel composite in a silylating solution comprising a dilution fluid and a first modifying agent, then adding a second modifying agent to the solution;
In one embodiment the dilution fluid is selected from hexane, heptane, octane, ethanol or isopropanol, in a concentration between 65% and 85% v/v in the silylating solution.
In one embodiment, the first modifying agent is present in the silylating solution in a concentration between 15% and 35% v/v.
In one embodiment the first modifying agent is selected from, but not limited to, hexamethyldisiloxane (HMDSO), hexamethyldisilazane (HMDZ), methyltrimethoxysilane (MTMS),
dimethoxydimethylsilane (DMDMS), among other organosilanes with non-hydrolysable methyl groups.
In one embodiment the second modifying agent is selected from TMCS, dimethyldichlorosilane or methyltrichlorosilane, but preferentially TMCS, and is present in the silylating solution in a concentration from 5% to 25% v/v.
The silylating solution is stirred for a time between 5 and 60 minutes.
- Incubating the composite aerogel in the silylating solution;
In one embodiment, the composite aerogel is incubated in the silylating solution at a temperature between 15 °C and 60 °C, for a time between 24 h and 96 hours.
- Drying the composite aerogel.
In one embodiment, the composite aerogel is dried temperatures between 50 °C and 200 °C, depending on the thermal stability of the reinforcing fibres.
In one embodiment, the fibres for composite reinforcement are selected from recycled tire fibres, glass fibres, glass wool, silica fibres, polyester fibres, or other type of organic or inorganic fibres.
The fibres are used either in the form of a blanket/ /mat/felt or used as loose fibres dispersed layer-by-layer in the mold.
In the context of this application, a fibre blanket is understood as a non-woven fibre network (for example like a felt), with the fibres randomly distributed or aligned in horizontal/longitudinal direction. In addition, when using recycled tire fibres, these can be assembled in a mat by needle-punching them before insertion in the mold.
Very good results were obtained when the silica fibres and polyester fibres (both in the form of felts), were used as reinforcement of the aerogel composites, these materials presenting superinsulation properties.
In the embodiment where recycled tire fibres are used for reinforcement, they can be used in their pristine state or after being modified by an acid solution pre-treatment.
The fibre pre-treatment step is achieved by mixing the tire fibres with an alcoholic solution comprising an oxidising agent. This mixture is stirred from 1 to 24 hours and then filtered. The fibres are then washed with alcohol, for example using the centrifuge, and then dried at a temperature between 40 °C and 250 °C.
In one embodiment the alcohol of this step is selected from, but not limited to, ethanol, methanol, isopropanol or butanol.
In one embodiment, the oxidizing agent of this step is selected from, but not limited to, peracetic acid, hydrogen peroxide, a mixture of acetic acid or acetic anhydride and hydrogen peroxide, sulfuric acid, and nitric acid, and is present in the pre-treatment alcoholic solution in a concentration 2 to 40% v/v.
In one embodiment, the alcohol to wash the fibres is selected from, but not limited to, methanol, ethanol, or isopropanol or mixtures thereof, used in a concentration varying from 50 to 95% v/v.
The fibre-reinforced rubber-silica aerogel composite disclosed in the present application is made from the mixing of silica and rubber sols, comprising from 5 to 25% w/w of rubber in the composite. It has negligible shrinkage, bulk density between 100 and 200 kg m3, contact angle with water between 120 and 160°, thermal conductivity between 14 and 30 mW.m_1-K_1, and with negligible weight loss up to 400 °C in the case of the more thermally stable fibres and inert atmosphere .
Examples
Materials
Tire rubber (diameter < 0.8 mm), ethanol (absolute, Fluka; C2H5OH), peracetic acid (38-40%, Merck; CH3CO3H), tetraethylorthosilicate (TEOS; purity ³ 99%, Aldrich; Si (OC2H5)4), ammonium hydroxide (25% NH3 in H2O, Fluka Analytical; NH4OH), n-hexane (C6H14, purity > 95%, Fisher Chemical), hexamethyldisiloxane (HMDSO, (CH3)3SiOSi(CH3)3, purity > 98%, Acros Organics), trimethylchlorosilane (TMCS, (CH3)3SiCl, purity ³ 98%, Sigma Aldrich) and several types of fibres were used in the composites production. The fibres acted as reinforcement of composites. The tire fibres include the following three main components: i) natural rubber and synthetic rubber polymers, ii) steel wire and iii) textile fibres (Nylon 6 and 66, Polyester, Kevlar, Rayon and Glass). A polyester fibre blanket, a silica fibre felt, and glass wool were also applied as alternatives to tire fibres.
1 . Aerogel composite synthesis
In the first step for the composite synthesis, 0.5 g of tire rubber was dissolved in a 10 mL solution containing ethanol and peracetic acid, with acid concentration of 5.0 vol.%. The solution was stirred for 24 h. After this period, a black colloidal solution was obtained. In one embodiment, the concentration of peracetic acid solution was 5 vol.% with a dissolution time of 24 h.
In the next step, the rubber colloidal solution was mixed with the silica sol. So, ethanol, TEOS and double distilled water were added, with a molar ratio of 10:1:4, to the rubber colloidal solution, and the mixture was stirred for 30 min. This solution was then stored in an oven at 27 °C for 24 h for the hydrolysis step. A basic solution, NH4OH 2.5 M, was added to the former solution and kept under strong agitation for 1 minute and then poured into the mold with the fibre blanket. The samples were kept in the oven at 27 °C during 5 days for aging.
Different types of fibres were used for the composites' reinforcement, from recycled tire fibres to glass/silica and polyester fibres. In the case of recycled tire fibres, they were used in their pristine state or after being modified by an acid solution treatment. For this treatment, 5 g of tire fibres were mixed with an alcoholic solution with 2.5 vol.% of peracetic acid. The mixture was stirred for 1-2 h and then filtered. The fibres were washed two times with ethanol using the centrifuge and then dried at 60 °C in an oven.
The composite aerogels were unmolded and washed with ethanol and hexane at 50 °C. The aerogel samples were then subjected to a surface modification. The silylating solution comprises
hexane, HMDSO and TMCS (70:20:10 volumetric percentages). First, hexane and HMDSO were added to the aerogel samples, and the solution was stirred for 30 min, and then TMCS was added, and the solution is stirred for another 30 min. The aerogel samples were immersed in the silylating solution and then placed in an oven at 50 °C and kept at that temperature for 8 h. After that, the samples are kept in the silylating solution for another 48 hours at a temperature between 15 and 35 °C. To dry the samples, the solution was removed, and the samples are kept in a hood for 24 h and then subjected to 100 °C for 3 h and 150 °C for 3 h.
2 . Characterization procedures
The properties of the final composite aerogel materials were assessed by different characterization techniques. The bulk density (pb) was calculated from the weight and volume of regular pieces of the samples. The chemical structure was evaluated by attenuated total reflection (ATR) Fourier- transform infrared spectroscopy (FTIR) (FT/IR 4200, Jasco), collecting the spectra between a wavenumber of 4000 and 400 cm-1, with 128 scans and 4 cm-1 of resolution. For the rubber, elemental analysis (EA) was also performed (EA 1108 CHNS-O, Fision Instruments), in terms of C, N, H and S elements. Scanning electron microscopy (SEM) images were obtained using a Compact/VPCompact FESEM (Zeiss Merlin) microscope, after coating the aerogel samples with a thin gold layer by Physical Vapor Deposition, during 20 s. Thermal properties were assessed by thermal gravimetric analysis and thermal conductivity. The thermal stability of different materials was obtained by using a DSC/TGA equipment (TGA-Q500, TA Instruments), from 20 °C to 800 °C, at a 10 °C.min_1 heating rate under nitrogen flow. Thermal conductivity, k, was measured with a Thermal Constants Analyzer TPS 2500 S (Hot
Disk), using the transient plane source method with two samples maintained at 20 °C. For samples with dimensions of 21.5 x 21.5 cm2, the thermal conductivity was also determined using Heat Flow Meter HFM 436/3/1 Lambda (EN 1946-1:1999), from NETZSCH, at 23 °C. The results obtained in this equipment are usually in close agreement with those obtained by the Guarded Hot Plate method [26].
For the composite with lower thermal conductivity, i.e. that reinforced with polyester fibres, the dynamic stiffness, st', was measured following the test procedures defined in standard ISO 9052-1 and the test-samples have a thickness of 15 mm and an area of 20.0 x 20.0 cm2.
Sorption tests were also performed with the composite reinforced with the polyester fibre blanket. The composite was placed floating on water with motor lubricant oil for 10 minutes and the percentage of oil removed from the water by the composite was recorded. The test samples have a thickness of 13 mm and an area 3.0 x 1.0 cm2 and they were turned 180° after 5 minutes of exposure.
2.1 Fibre characterization
2.1.1 Recycled tire fibre
FTIR analysis was also performed in the recycled tire fibre, and the spectrum is presented in Figure 2a. The spectrum shows different bands that can be attributed to: (1) hydroxyl groups; (2) stretching vibration of hydrogen bonds in amide II and/or -NH- stretching; (3) and (4) aliphatic C-H stretching; (5) stretching of C=0 of carboxylic acid group; (6) bending vibrations in hydrogen bonds of amide in mode I and/or -C=0 stretching; (7) bending vibrations in hydrogen bonds of amide in mode II and/or combined N-H deformation and C-N stretching vibration modes; (8) -CH2- scissors vibration; (9) -CH2- scissors vibration and/or para-
substituted benzene ring; (10) -CH3 group deformation; (11) -CH2 wagging; (12) (C=0)-C stretching of ester group; (13) and (14) O-CH2 stretching; (15) Para-substituted benzene ring; (16) trans O-CH2 stretching; (17) Para-substituted benzene ring and/or out of plane vibration of aromatic C-H;
(18) trans CH2 rocking; (19) C=0 + CCO bending and/or vibrations of adjacent two aromatic H in p-substituted compounds; (20) interaction of polar ester groups and benzene rings and/or bending of aromatic C-C ; (21) and (22) are assigned to the torsion in hydrogen bonds of the mode I and mode II of amide.
After analysis the FTIR results, it was possible to confirm the presence of two main types of fibres: (1) a polyester fibre - poly(ethylene terephthalate) (PET) fibre, and (2) a polyamide fibre - nylon 6,6. The bands associated with the polyester fibres in the FTIR spectra are 1, 3, 5, 9, 11-20, while for the polyamide, the bands are 2, 4, 6-10; 21, 22.
These findings are in agreement with the literature, as PET and nylon 6,6 are the most commonly used polymers in tires. However, other fibres such as glass or rayon can also be present in the textile fibre used, but in lower amounts than the ones detected by FTIR analysis.
The TGA analysis (Figure 2b) of the recycled tire fibres also indicates a mixture of fibres, as detected in FTIR, as a two-step process was observed. However, for both fibres found in the chemical characterization (PET and Nylon 6,6), higher onset temperatures were expected (around 400 °C). The first degradation step consisted in a weight loss of 11.4% with an onset temperature of 324.3 °C, and the second step showed a weight loss of 66 % and onset temperature of 377
°C, with a maximum at 417 °C. The thermal degradation between 25-100 °C can be attributed to the loss of water. It is possible that the first degradation step is related to the other fibres present in the mixture, such as rayon fibre, that presents a thermal degradation temperature between 250 °C and 350 °C, while the second step is attributed to the degradation of both polyester and polyamide fibres.
The thermal conductivity of this fibre mat is 67.50 ± 0.14 mW.m_1.K_1 (Hot Disk). This result is lower than the one obtained for the rubber (91.09 ± 0.13 mW.m_1.K_1), but still higher than common materials used for thermal insulation, as previously described.
2.1.2 Polyester Fibre
Polyester fibre blanket was also submitted to FTIR analysis, and the spectrum is presented in Figure 3a. The spectrum shows different bands that can be attributed to: (1) hydroxyl groups; (2) aromatic C-H stretching; (3) and (4) aliphatic C-H stretching; (5) Stretching of C=0 of carboxylic group; (6) and (7) interplane skeletal vibrations of the aromatic ring; (8) CH2 bending; (9) Para-substituted benzene ring and/or in plane deformation of aromatic C-H and/or stretching of aromatic C-C; (10) CH2 wagging; (11) (C=0)-C stretching of ester group; (12) Para-substituted benzene ring and/or or in plane bending of aromatic C-H; (13) and (14) O-CH2 stretching; (15) Para-substituted benzene ring; (16) trans O-CH2 stretching; (17) Para-substituted benzene ring and/or out of plane vibration of aromatic C-H; (18) trans C¾ rocking; (19) C=0 + CCO bending and/or vibrations of adjacent two aromatic H in p-substituted compounds; (20) interaction of polar ester groups and benzene rings and/or bending of aromatic C-C. After analysis of the FTIR results, it was
confirmed that the polyester fibre used in this work is a poly (ethylene terephthalate) (PET) fibre.
The thermal stability of the polyester fibres was investigated using TGA measurement, Figure 3b. The TGA data showed an onset temperature of 406 °C, and total weight loss of 77.5%, which is in agreement with the literature data for PET samples. The thermal conductivity of the PET was also assessed, with a value of 33.90 ± 0.05 mW.m_1.K_1 (Hot Disk). This result is much lower than the ones obtained for the rubber and the recycled tire fibres, however, it is still higher than the very low thermal conductivities of silica aerogels, that are typically in the order of 15 mW.m_1.K_1, at ambient temperature, pressure and relative humidity.
2.1.3 Silica fibre
The silica fibre felt was also analysed by FTIR, and the spectrum is presented in Figure 4a. The spectrum of this inorganic fibre shows different bands that can be attributed to: (1) silanol groups; (2) stretching of aliphatic C-H groups; (3) asymmetric bending of C-H groups; (4) and (5) asymmetric stretching vibration of Si-O-Si groups; and (6) Si-0 symmetric stretching vibration. The C-H groups are due to a thin coating of varnish on the top of the fibre felt. The thermal degradation of the silica fibres was assessed through thermal gravimetric analysis. As observed in Figure 4b, this fibre only presented one small weight loss (around 3.9%), with an onset temperature of 270 °C, that is attributed to the degradation of the finishing organic coating. The silica fibres presented a thermal conductivity of 29.08 ± 0.20 mW.m_1.K_1 (Hot Disk), the lowest between the fibres used in this work, however, as already mentioned, it
is still higher than the values obtained for the silica aerogels.
2.1.4 Glass wool
FTIR analysis was also performed at Glass wool, and the spectrum is presented in Figure 5a. The spectrum of the glass wool shows similar bands as the ones obtained for the silica felt as expected, since both materials are mainly composed by S1O2, and these bands can be attributed to: (1) stretching of C=C; (2) deformation vibration of C-H; (3) symmetric deformation vibration of C-H; (4) asymmetric stretching vibration of Si-O-Si groups; (5) in-plane stretching vibration of Si-0 groups and (6) Si-0 symmetric stretching vibration.
Regarding the thermal stability of glass wool, the weight loss of around 35% observed in the TGA (Figure 5b) is probably due to the evaporation of adsorbed water and the degradation of organic compounds added/adsorbed in the sample during the manufacturing process. This also explains the C-containing bonds found in the FTIR spectrum. The thermal conductivity of the glass wool was also measured, and the sample had a value of 56.71 ± 0.03 mW.m_1.K_1 (Hot Disk).
2.2 Composite aerogel characterization
Table 1 shows some composites' properties and Figure 1 the macro-photographs of the samples. The composites displayed negligible shrinkage during the drying step (Table 1), thus keeping intact the pore structure of the gel, which contributes to the excellent insulation performance and sorption capacity.
Two main factors contribute to the absence of shrinkage. First, when fibres are added into the aerogel matrix, they are able to resist lateral capillary stresses developed during the drying procedure and thus act as supporting skeleton. The second factor is related to the modification of the silica matrix. After the modification step, the silica gel has a hydrophobic character (Table 1, see contact angle), which makes possible the "spring-back" effect of the matrix (reversible shrinkage). During ambient pressure drying, first there is a contraction of the gel due to capillary pressure, followed by a partial recover to its initial volume. This recovery is caused by the presence of non condensable moieties/non-polar groups grafted in the silica matrix surface. With the simultaneous use of HMDSO and TMCS in the modification step, almost all OH groups are converted to 0-Si-(CH3)3. The CH3 groups on the surface repel each other during the drying, leading to the referred "spring-back" effect.
The individual reactivities of HMDSO and TMCS are complementary; TMCS enhances the reactivity of HMDSO, since the HC1 needed for the cision of the HMDSO is formed during the reaction of TMCS with silica pendant hydroxyl groups. The occurring reactions are displayed in Figure 6. As these chain reactions occur, they enhance the surface modification and lead to the formation of an aerogel matrix with uniform structure and low density, as observed in the composites here developed.
Comparing the composites in Table 1, a lower value of bulk density was obtained for the composite synthesized with the polyester fibre blanket, silica fibre blanket and glass wool, with these being lower than the values obtained for the composites with recycled tire fibre, which contributes to
better insulation properties. This difference is mainly due to the different densities of the fibres themselves, with the recycled tire fibre having 144.2 kg.m-3 while for example the polyester has a density lower than 10 kg.m-3.
Even though a high value was obtained for the composite with recycled tire fibre, the materials have densities in the same range of other fibre-reinforced silica aerogel composites dried in ambient pressure conditions.
In aerogels, the density has a high influence in the thermal conductivity of the samples, with most of the relevant superinsulating S1O2 aerogels commercially available having densities between 80 and 200 kg m-3.
As all materials in Table 1 have densities in this range, the thermal conductivities of the developed composite are expected to be very low and were assessed by two techniques.
This particular property is a crucial factor to establish the possibility of applying the developed composites as thermal insulators. The aerogel composite materials with recycled tire fibres and glass wool have higher values of thermal conductivity than the ones with polyester fibres and silica fibres. This was expected due to the different values for this property displayed by the fibres themselves, which dominates over the effect of density, because the fibres constitute an interconnected network that favours the heat transfer through the composite.
It is important to mention that the addition of the recycled rubber sol into the silica sol did not cause an increase in thermal conductivity of the final aerogel. The pure silica aerogel, TEOS-based matrix with the same modification procedure than the composites, has a thermal conductivity of
24.67 ± 0.14 mW.iti-1.K_1, while the rubber-silica aerogel (addition of rubber into the TEOS sol and modified with HMDSO/TMCS) exhibits a value of 24.82 ± 0.05 mW.m_1.K_1, when measuring by Hot Disk transient method. The similar values of both aerogels indicate a good interaction between the two phases to form the three-dimensional network, which was later confirmed by SEM images.
When measured with a steady-state thermal conductivity method, all composites disclosed in Table 1 display lower thermal conductivities than the typical building insulation materials used in walls such as fibreglass (33-40 mW.m_1.K 1), rockwool (37 mW.nr1.K_1), polyethylene (41 mW.nr1.K_1), expanded polystyrene (37-38 mW.nr1.K_1), extruded polystyrene (30-32 mW.nr1.K_1) and cellulose (46-54 mW.m_1.K_1).
The lowest values were achieved by the polyester and silica fibres-silica/rubber aerogel composites, that have a thermal conductivity lower than 25 mW.m_1.K_1, being classified as a superinsulating materials.
Table 1 - Structural and thermal properties and hydrophobicity of the aerogel composites.
a Panels with 21.5 x 21.5 cm2 of area.
In order to estimate the thermal stability of the composite materials, all aerogel samples were submitted to a thermogravimetric analysis from 20 °C to 600 °C, under N2 atmosphere (Figure 7).
For the composite with recycled tire fibres, a significant weight loss was detected, Figure 7a, with four phenomena being observed. The first weight loss starts right at room temperature (20-25°C) and is due to adsorbed water and residual solvents/by-products of the synthesis procedure (Tonset = 50.2 °C). The second phenomenon, onset temperature of 179 °C, can be attributed to the loss of structural hydroxyl groups of the silica matrix. The third and fourth weight losses (Tonset = 255 °C and 388 °C, respectively) are mainly due to the thermal degradation of the composites' fibres, first fibres such as rayon and later the polyester and polyamide fibres. However, the last phenomenon has also the contribution of the decomposition of methyl groups attached to the silica surface after the modification with
HMDSO and TMCS.
For the composites made with polyester fibres, only a small weight loss was observed, around 8.5% (Figure 7b). The onset temperature was around 458 °C, much higher than the values obtained for the composite with recycled tire fibres. Very similar results were obtained for the samples obtained with silica fibres and glass wool (7c and 7d), with these composites presenting weight losses of 8.09% and 5.53%, and onset temperatures of 483 °C and 448 °C, respectively. The weight losses here observed are attributed to the thermal decomposition of the silica surface's methyl groups from silylation, as also verified in the other composite material, and overlapped with the onset of polyester degradation (when applicable) . After the degradation of -CH3 surface groups, it is expected that the materials lose the hydrophobic character of the modified aerogel.
A significant difference in the thermal degradation of the developed composites with organic fibres was observed in thermogravimetric analysis and is probably due to the different interaction of the rubber-silica aerogel with the fibres, as observed in the SEM images (Figure 8). In the case of polyester composites, the aerogel was able to completely cover the fibres (Figure 8c), increasing their thermal stability, while for the recycled tire fibres this was not observed (Figure 8a) and most of the fibres were still exposed. In the case of polyester fibres, it is easily observed that the aerogel grew around the fibre following the fibres' shape, while for the composites with the recycled tire fibres, the fibres do not interact significantly with the aerogel, with a clear separation between both phases. For the composites with silica fibres and glass wool (Figures 8e and 8g), some degree of interaction occurs between the two phases, with some of the fibres being covered by the
aerogel while other remain exposed. For these two composites the interaction was not as good as in the case of polyester fibres (Figure 8c). However, in the case of silica fibres and glass wool the fibres themselves are quite stable up to the tested temperature in thermal analysis (600 °C), due to their predominant S1O2 composition.
Regarding the aerogel phase, all samples show similar microstructures (Figure 8) with an interconnected three- dimensional aerogel matrix. Thus, even though the interaction between both phases is different, it can be concluded that the type of fibres used does not affect the formation of the porous structure of the matrices. It was also verified that the presence of colloidal rubber did not prevent the formation of the network or interfered in the typical silica aerogel structure, as both samples present similar structures verified in other modified TEOS-based materials.
The mechanical behaviour of these materials was assessed by uniaxial compression tests, and the results are presented in Figure 9.
The material's capacity of recovery to its original shape is important for building applications, as it can regain its original shape after compression. This flexible behaviour also allows to adapt better to curved surfaces. Thus, recovery tests were performed submitting the samples to 10% and 25% strain (Figures 9a and 9c). The results indicate an excellent behaviour, as the samples are able to almost completely recover the original size, either after 10% strain or 25% strain (Figure 9 and Table 2), always above 94%, and
in the case of polyester fibres and glass wool the observed recoveries exceeded 99%.
In order to further evaluate the capacity of the material to withstand dimensional load, axial cyclic compression tests (10 cycles) were performed until a strain of 10% (Figure 9c). After the test, the samples only display small reductions of their initial height (Table 2). These results indicate an excellent mechanical performance of the composites, in terms of flexibility, especially if compared with pristine silica aerogels. They are able to withstand cyclic loads without disintegration, which is an important feature for vibration dissipation and damping.
The samples were also submitted to a destructive test with the load cell of 3 kN, up to the maximum allowed force (Figure 9). Figure 9d presents the non-linear stress-strain curve, in which the compression progress of the sample
contains three stages. At the first stage, with the strain ranging from 0% to around 30%, known as linear stage, the slope of the compression curve remains unchanged, and the open pores act as the main support of the composite. The second stage, the yielding stage (strain in the range of 30% to 60%), the stress increases at a fixed rate and the fibres become the main load-bearing part. In the final part, the densification stage (from 60% to ~95%), the collapse of the aerogel part and a significant increase in the curve slope are observed.
The samples did not recover their original height after the applied load was removed, as expected for this destructive test.
The measured dynamic stiffness of the new aerogel composite with polyester fibres was 11 MN.m-3. In comparison with other materials (e.g., recycled tyre rubber: 61 MN.m-3, and cork/rubber composite: 184 MN.m-3) the measured dynamic stiffness of the new aerogel composite is significantly lower.
Sorption tests for lubricant oil were carried out with the polyester-reinforced rubber-silica composites. The adsorption capacity of the composite was calculated in the first 5 min and it showed a value of 9.83 g.g-1. The values obtained for removal are very high, 97%; this composite could be a very promising sorbent for oil spill cleaning.
This description is of course not in any way restricted to the forms of implementation presented herein and any person with an average knowledge of the area can provide many possibilities for modification thereof without departing from the general idea as defined by the claims. The preferred
forms of implementation described above can obviously be combined with each other. The following claims further define the preferred forms of implementation.
References
[1] P. Grammelis, N. Margaritis, P. Dallas, D. Rakopoulos, and G. Mavrias, "A Review on Management of End of Life Tires (ELTs) and Alternative Uses of Textile Fibers," Energies, vol. 14, no. 3, p. 571, 2021.
[2] "Global Tire Recycling Industry Analysis By Rubber Type, By Product Type, By End User And By Geography & COVID- 19 Impact With Market Outlook 2017-2030," 2020.
[3] European Parliament and Council, "Directive 2008/98/EC of the European Parliament and of the Council of 19 November 2008 on waste and repealing certain directives." Official Journal of the European Union, pp . 3-30, 2008, doi: 2008/98/EC.; 32008L0098.
[4] M. Gharfalkar, R. Court, C. Campbell, Z. Ali, and G. Hillier, "Analysis of waste hierarchy in the European waste directive 2008/98/EC," Waste Manag., vol. 39, pp. 305-313, 2015, doi: https://doi.Org/10.1016/j.wasman.2015.02.007.
[5] B. Acevedo, A. M. Fernandez, and C. Barriocanal, "Identification of polymers in waste tyre reinforcing fibre by thermal analysis and pyrolysis," J.Anal. Appl. Pyrolysis, vol. Ill, pp. 224-232, 2015.
[6] M. Sienkiewicz, H. Janik, K. Borzgdowska-Labuda, and J. Kucihska-Lipka, "Environmentally friendly polymer-rubber composites obtained from waste tyres: A review," J. Clean. Prod., vol. 147, pp. 560-571, 2017.
[7] Q. B. Thai, T. E. Siang, D. K. Le, W. A. Shah, N. Phan- Thien, and H. M. Duong, "Advanced fabrication and multi properties of rubber aerogels from car tire waste," Colloids
Surfaces A Physicochem. Eng. Asp., vol. 577, pp. 702-708,
2019.
[8] C. Dwivedi, S. Manjare, and S. K. Rajan, "Recycling of waste tire by pyrolysis to recover carbon black: Alternative & environment-friendly reinforcing filler for natural rubber compounds," Compos. Part B Eng., vol. 200, p. 108346, 2020.
[9] M. Passaponti, L. Rosi, M. Savastano, W. Giurlani, H. A. Miller, A. Lavacchi, J. Filippi, G. Zangari, F. Vizza, and M. Innocenti, "Recycling of waste automobile tires: Transforming char in oxygen reduction reaction catalysts for alkaline fuel cells," J. Power Sources, vol. 427, pp. 85-90, 2019.
[10] C. Wang, D. Li, T. Zhai, H. Wang, Q. Sun, and H. Li, "Direct conversion of waste tires into three-dimensional graphene," Energy Storage Mater., vol. 23, pp. 499-507, 2019.
[11] D. R. Burfiel, K.-L. Lim, and K.-S. Law, "Epoxidation of natural rubber latices: methods of preparation and properties of modified rubbers," J. Appl- Polym. Sci., vol. 29, pp. 1661-1673, 1984.
[12] I. R. Gelling, "Modification of natural rubber latex with peracetic acid," Rubber Chem. Technol., vol. 58, pp. 86-96, 1985.
[13] N. V. Bac, M. Mihailov, and L. Terlemezyan, "On the stability of natural rubber latex acidified by acetic acid and subsequent epoxidation by peracetic acid," Eur. Polym. J., vol. 27, pp. 557-563, 1991.
[14]B. K. Easton, N. Weinberg, and A. P. Shutts, "Peracetic acid treatment of vulcanized rubber," U.S. Patent No. 2,873,213, 10 Feb 1959.
[15] T. Sakaki, L. Tarachiwin, K. Charungchitaree, H. Kum- Ourm, "Method for producing an epoxidized natural rubber, rubber composition for tires, and pneumatic tire," U.S. Patent No. 9,193,806, 24 Nov 2015.
[16] S. Miyazaki, "Method for producing epoxidized natural rubber, rubber composition for tires, and pneumatic tire," U.S. Patent No. 9,567,407, 14 Feb 2017.
[17] 0. R. Evans, W. Dong, and K. Despande, "Sulfur- containing organic-inorganic hybrid gel compositions and aerogels," U.S. Patent No. 9,133,280, 15 Sep 2015.
[18] CN108102130A
[19] CN110655725A
[20] W02015045211A1
[21] M. Omansky, "Composition of unvulcanized crepe rubber," U.S. Patent No. 2,269,377, 6 Jan 1942.
[22]N. K. On, A. A. Rashid, M. M. M. Nazlan, and H. Hamdan, "Thermal and mechanical behavior of natural rubber latex- silica aerogel film," J.Appl. Polym. Sci, vol. 124, pp.3108- 3116, 2012.
[23] Q. B. Thai, T. E. Siang, D. K. Le, W. A. Shah, N. Phan- Thien, and H. M. Duong, "Advanced fabrication and multi properties of rubber aerogels from car tire waste," Colloids Surf. A, vol. 577, pp. 702-708, 2019.
[24] Q. B. Thai, R. 0. Chong, P. T. T. Nguyen, D. K. Le, P. K. Le, N. Phan-Thien, and H. M. Duong, "Recycling of waste tire fibers into advanced aerogels for thermal insulation and sound absorption applications," J. Environ. Chem. Eng., vol. 8, 104279, 2020.
[25] Q. B. Thai, D. K. Le, N. H. N. Do, P. K. Le, N. Phan- Thien, C. Y. Wee, and H. M. Duong, "Advanced aerogels from waste tire fibers for oil spill-cleaning applications", J. Environ. Chem. Eng., vol. 8, 104016, 2020.
[26] NETZSCH, "Heat Flow Meter - HEM 436 Lambda - High Precision Instrument for Testing Insulating Materials Compliant to ASTM C518, ISO 8301, JIS A1412 and DIN EN 1266."
Claims
1. A fibre-reinforced rubber-silica aerogel composite comprising silica and tire rubber and being reinforced with fibres, wherein the composite comprises from 5 to 25% w/w of rubber, has a bulk density between 100 and 200 kg m-3, contact angle with water between 120 and 160° and thermal conductivity between 14 and 30 mW.m_1-K_1.
2. Method to produce the fibre-reinforced rubber-silica aerogel composite of claim 1, comprising the following steps: dissolving tire rubber in a solution comprising an oxidising agent and stirring to obtain a rubber colloidal solution, wherein the tire rubber is present in an amount from 1 to 10% w/v in the rubber colloidal solution;
- mixing the previous rubber colloidal solution with a solution comprising a silane, an alcohol and water;
- adding an aqueous basic catalyst solution to the previous mixture;
- pouring the previous mixture into a mold comprising fibres to form the aerogel composite;
- unmolding the aerogel composite and washing it first with an alcohol solution and afterwards with a non-polar solvent;
- modifying the surface of the aerogel composite by immersing the aerogel composite in a silylating solution comprising a dilution fluid and a first modifying agent, then adding a second modifying agent to the solution, and incubating the aerogel composite in the solution;
- drying the composite aerogel.
3. Method according to the previous claim, wherein the tire rubber is used with a particle diameter lower than 1 mm.
4. Method according to any of the claims 2 to 3, wherein alcohol is further added to the rubber and oxidising agent solution and is selected from methanol, ethanol, n-propanol, isopropanol, or mixtures thereof.
5. Method according to any of the claims 2 to 4, wherein the oxidizing agent is selected from peracetic acid, hydrogen peroxide, sulfuric acid, and nitric acid, a mixture of acetic acid or acetic anhydride and hydrogen peroxide, and is present in a concentration varying from 2% to 40% v/v of the rubber colloidal solution.
6. Method according to any of the claims 2 to 5, wherein the molar ratio between silane and alcohol in the solution varies from 1:5 to 1:35.
7. Method according to any of the claims 2 to 6, wherein silane is selected from tetramethylorthosilicate (TMOS), tetraethylorthosilicate (TEOS), methyltrimethoxysilane (MTMS), 3-aminopropyltrimethoxysilane (APTMS), aminopropyltriethoxysilane (APTES), vinyltrimethoxysilane (VTMS), or mixtures thereof.
8. Method according to any of the claims 2 to 9, wherein the aqueous basic catalyst is selected from ammonium hydroxide, sodium hydroxide, potassium hydroxide, ammonium carbonate, among other basic catalysts, and the concentration in the aqueous basic catalyst solution varies from 1 rnol.L-1 to 15 mol.L_1.
9. Method according to any of the claims 2 to 8, wherein the fibres are used in their loose form or in the form of a blanket/mat/felt .
10. Method according to any of the claims 2 to 9, wherein the solvent of the silylating solution is selected from hexane, heptane, octane, ethanol or isopropanol.
11. Method according to any of the claims 2 to 10, wherein the first modifying agent is selected from, hexamethyldisiloxane (HMDSO), hexamethyldisilazane (HMDZ), methyltrimethoxysilane (MTMS), dimethoxydimethylsilane (DMDMS), among other organosilanes with non-hydrolysable methyl groups, and is present in the sylilating solution in a concentration between 15% and 35% v/v.
12. Method according to any of the claims 2 to 11, wherein the second modifying agent is selected from trimethylchlorosilane, dimethyldichlorosilane or methyltrichlorosilane, and is present in the silylating solution in a concentration from 5% to 25% v/v.
13. Method according to any of the claims 2 to 12, wherein fibres are selected from recycled tire fibres, glass fibres, glass wool, silica fibres, polyester fibres, or other type of organic or inorganic fibres, either in the form of loose fibres or as a blanket or felt.
14. Method according to any of the claims 2 to 13, wherein the fibres are pre-treated with an alcoholic solution comprising an oxidising agent, stirred from 1 to 24 hours, filtered, washed and dried.
15. Use of the fibre-reinforced rubber-silica aerogel composite of any of the previous claims as a thermal
insulator, as an acoustic insulator, or as an adsorbent material.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
PT11728521 | 2021-06-11 | ||
PT117285 | 2021-06-11 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2022259044A1 true WO2022259044A1 (en) | 2022-12-15 |
Family
ID=80448415
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/IB2022/050094 WO2022259044A1 (en) | 2021-06-11 | 2022-01-06 | Fibre-reinforced aerogel composites from mixed silica and rubber sols and a method to produce the rubber-silica aerogel composites |
Country Status (1)
Country | Link |
---|---|
WO (1) | WO2022259044A1 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20230220167A1 (en) * | 2022-01-10 | 2023-07-13 | Ford Global Technologies, Llc | Sustainable tire waste aerogel with tunable flexibility made from recycled tires for automotive applications |
Citations (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2269377A (en) | 1938-11-23 | 1942-01-06 | Monsanto Chemicals | Composition of unvulcanized crepe rubber |
US2873213A (en) | 1956-10-24 | 1959-02-10 | Fmc Corp | Peracetic acid treatment of vulcanized rubber |
US20130005842A1 (en) * | 2011-06-30 | 2013-01-03 | Aspen Aerogels, Inc. | Sulfur-containing organic-inorganic hybrid gel compositions and aerogels |
CN102923723A (en) * | 2012-10-30 | 2013-02-13 | 陕西盟创纳米新型材料股份有限公司 | Novel aerosol material and preparation method, application and application structure thereof |
US9193806B2 (en) | 2012-01-23 | 2015-11-24 | Sumitomo Rubber Industries, Ltd. | Method for producing an epoxidized natural rubber, rubber composition for tires, and pneumatic tire |
CN105439505A (en) * | 2015-11-17 | 2016-03-30 | 刘朝辉 | SiO2 aerogel mortar and preparation method thereof |
US9567407B2 (en) | 2012-03-08 | 2017-02-14 | Sumitomo Rubber Industries, Ltd. | Method for producing epoxidized natural rubber, rubber composition for tires, and pneumatic tire |
WO2017075554A1 (en) * | 2015-10-29 | 2017-05-04 | Golfetto Michael | Methods freeze drying and composite materials |
CN107244882A (en) * | 2017-06-20 | 2017-10-13 | 成都新柯力化工科技有限公司 | A kind of aerosil felt and preparation method thereof |
-
2022
- 2022-01-06 WO PCT/IB2022/050094 patent/WO2022259044A1/en unknown
Patent Citations (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2269377A (en) | 1938-11-23 | 1942-01-06 | Monsanto Chemicals | Composition of unvulcanized crepe rubber |
US2873213A (en) | 1956-10-24 | 1959-02-10 | Fmc Corp | Peracetic acid treatment of vulcanized rubber |
US20130005842A1 (en) * | 2011-06-30 | 2013-01-03 | Aspen Aerogels, Inc. | Sulfur-containing organic-inorganic hybrid gel compositions and aerogels |
US9133280B2 (en) | 2011-06-30 | 2015-09-15 | Aspen Aerogels, Inc. | Sulfur-containing organic-inorganic hybrid gel compositions and aerogels |
US9193806B2 (en) | 2012-01-23 | 2015-11-24 | Sumitomo Rubber Industries, Ltd. | Method for producing an epoxidized natural rubber, rubber composition for tires, and pneumatic tire |
US9567407B2 (en) | 2012-03-08 | 2017-02-14 | Sumitomo Rubber Industries, Ltd. | Method for producing epoxidized natural rubber, rubber composition for tires, and pneumatic tire |
CN102923723A (en) * | 2012-10-30 | 2013-02-13 | 陕西盟创纳米新型材料股份有限公司 | Novel aerosol material and preparation method, application and application structure thereof |
WO2017075554A1 (en) * | 2015-10-29 | 2017-05-04 | Golfetto Michael | Methods freeze drying and composite materials |
CN105439505A (en) * | 2015-11-17 | 2016-03-30 | 刘朝辉 | SiO2 aerogel mortar and preparation method thereof |
CN107244882A (en) * | 2017-06-20 | 2017-10-13 | 成都新柯力化工科技有限公司 | A kind of aerosil felt and preparation method thereof |
Non-Patent Citations (21)
Title |
---|
B. ACEVEDOA. M. FERNANDEZC. BARRIOCANAL: "Identification of polymers in waste tyre reinforcing fibre by thermal analysis and pyrolysis", J. ANAL. APPL. PYROLYSIS, vol. 111, 2015, pages 224 - 232 |
C. DWIVEDIS. MANJARES. K. RAJAN: "Recycling of waste tire by pyrolysis to recover carbon black: Alternative & environment-friendly reinforcing filler for natural rubber compounds", COMPOS. PART B ENG., vol. 200, 2020, pages 108346, XP086274963, DOI: 10.1016/j.compositesb.2020.108346 |
C. WANGD. LIT. ZHAIH. WANGQ. SUNH. LI: "Direct conversion of waste tires into three-dimensional graphene", ENERGY STORAGE MATER, vol. 23, 2019, pages 499 - 507 |
D. R. BURFIELK.-L. LIMK.-S. LAW: "Epoxidation of natural rubber latices: methods of preparation and properties of modified rubbers", J. APPL- POLYM. SCI., vol. 29, 1984, pages 1661 - 1673 |
DATABASE WPI Week 201376, Derwent World Patents Index; AN 2013-H84382, XP002806260 * |
DATABASE WPI Week 201645, Derwent World Patents Index; AN 2016-21506G, XP002806262 * |
DATABASE WPI Week 201782, Derwent World Patents Index; AN 2017-71931H, XP002806261 * |
EUROPEAN PARLIAMENT AND COUNCIL: "Directive 2008/98/EC of the European Parliament and of the Council of 19 November 2008 on waste and repealing certain directives", OFFICIAL JOURNAL OF THE EUROPEAN UNION, 2008, pages 3 - 30 |
GLOBAL TIRE RECYCLING INDUSTRY ANALYSIS BY RUBBER TYPE, BY PRODUCT TYPE, BY END USER AND BY GEOGRAPHY & COVID-19 IMPACT WITH MARKET OUTLOOK 2017-2030, 2020 |
I. R. GELLING: "Modification of natural rubber latex with peracetic acid", RUBBER CHEM. TECHNOL., vol. 58, 1985, pages 86 - 96, XP008162724, DOI: 10.5254/1.3536060 |
M. GHARFALKARR. COURTC. CAMPBELLZ. ALIG. HILLIER: "Analysis of waste hierarchy in the European waste directive 2008/98/EC", WASTE MANAG, vol. 39, 2015, pages 305 - 313 |
M. PASSAPONTIL. ROSIM. SAVASTANOW. GIURLANIH. A. MILLERA. LAVACCHIJ. FILIPPIG. ZANGARIF. VIZZAM. INNOCENTI: "Recycling of waste automobile tires: Transforming char in oxygen reduction reaction catalysts for alkaline fuel cells", J. POWER SOURCES, vol. 427, 2019, pages 85 - 90, XP085718104, DOI: 10.1016/j.jpowsour.2019.04.067 |
M. SIENKIEWICZH. JANIKK. BORZEDOWSKA-LABUDAJ. KUCINSKA-LIPKA: "Environmentally friendly polymer-rubber composites obtained from waste tyres: A review", J. CLEAN. PROD., vol. 147, 2017, pages 560 - 571, XP029930237, DOI: 10.1016/j.jclepro.2017.01.121 |
N. K. ONA. A. RASHIDM. M. M. NAZLANH. HAMDAN: "Thermal and mechanical behavior of natural rubber latex-silica aerogel film", J. APPL. POLYM. SCI, vol. 124, 2012, pages 3108 - 3116 |
N. V. BACM. MIHAILOVL. TERLEMEZYAN: "On the stability of natural rubber latex acidified by acetic acid and subsequent epoxidation by peracetic acid", EUR. POLYM. J., vol. 27, 1991, pages 557 - 563 |
NETZSCH, HEAT FLOW METER - HFM 436 LAMBDA - HIGH PRECISION INSTRUMENT FOR TESTING INSULATING MATERIALS - COMPLIANT TO ASTM C518, ISO 8301, JIS A1412 AND DIN EN 1266 |
P. GRAMMELISN. MARGARITISP. DALLASD. RAKOPOULOSG. MAVRIAS: "A Review on Management of End of Life Tires (ELTs) and Alternative Uses of Textile Fibers", ENERGIES, vol. 14, no. 3, 2021, pages 571 |
Q. B. THAID. K. LEN. H. N. DOP. K. LEN. PHAN-THIENC. Y. WEEH. M. DUONG: "Advanced aerogels from waste tire fibers for oil spill-cleaning applications", J. ENVIRON. CHEM. ENG., vol. 8, 2020, pages 104016 |
Q. B. THAIR. 0. CHONGP. T. T. NGUYEND. K. LEP. K. LEN. PHAN-THIENH. M. DUONG: "Recycling of waste tire fibers into advanced aerogels for thermal insulation and sound absorption applications", J. ENVIRON. CHEM. ENG., vol. 8, 2020, pages 104279 |
Q. B. THAIT. E. SIANGD. K. LEW. A. SHAHN. PHAN-THIENH. M. DUONG: "Advanced fabrication and multi-properties of rubber aerogels from car tire waste", COLLOIDS SURF. A, vol. 577, 2019, pages 702 - 708, XP085747863, DOI: 10.1016/j.colsurfa.2019.06.029 |
Q. B. THAIT. E. SIANGD. K. LEW. A. SHAHN. PHAN-THIENH. M. DUONG: "Advanced fabrication and multi-properties of rubber aerogels from car tire waste", COLLOIDS SURFACES A PHYSICOCHEM. ENG. ASP, vol. 577, 2019, pages 702 - 708, XP085747863, DOI: 10.1016/j.colsurfa.2019.06.029 |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20230220167A1 (en) * | 2022-01-10 | 2023-07-13 | Ford Global Technologies, Llc | Sustainable tire waste aerogel with tunable flexibility made from recycled tires for automotive applications |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
Thai et al. | Advanced fabrication and multi-properties of rubber aerogels from car tire waste | |
Nguyen et al. | Green aerogels from rice straw for thermal, acoustic insulation and oil spill cleaning applications | |
Chen et al. | One-pot synthesis of monolithic silica-cellulose aerogel applying a sustainable sodium silicate precursor | |
Peng et al. | Facile preparation for gelatin/hydroxyethyl cellulose‐SiO2 composite aerogel with good mechanical strength, heat insulation, and water resistance | |
Mathew et al. | Swelling behaviour of isora/natural rubber composites in oils used in automobiles | |
JP2008537570A (en) | A process for producing monolithic xerogels and aerogels composed of silica / latex hybrids modified with alkoxysilane groups under subcritical conditions. | |
Shi et al. | Novel sound insulation materials based on epoxy/hollow silica nanotubes composites | |
Sequeira et al. | Preparation and properties of cellulose/silica hybrid composites | |
Verdolotti et al. | “Aerogel-like” polysiloxane-polyurethane hybrid foams with enhanced mechanical and thermal-insulating properties | |
KR20170134424A (en) | Production method of porous body and porous body | |
WO2022259044A1 (en) | Fibre-reinforced aerogel composites from mixed silica and rubber sols and a method to produce the rubber-silica aerogel composites | |
Afolabi et al. | Fabrication and characterization of two-phase syntactic foam using vacuum assisted mould filling technique | |
TW201819476A (en) | Polysiloxane based aerogels | |
Bach et al. | Effects of co-silanized silica on the mechanical properties and thermal characteristics of natural rubber/styrene-butadiene rubber blend | |
Wenbo et al. | Sound absorption behavior of polyurethane foam composites with different ethylene propylene diene monomer particles | |
Yao et al. | Freezing-extraction/vacuum-drying method for robust and fatigue-resistant polyimide fibrous aerogels and their composites with enhanced fire retardancy | |
Huang et al. | Understanding the reinforcement effect of fumed silica on silicone rubber: Bound rubber and its entanglement network | |
Zhan et al. | Effect of aromatic amine modified graphene aerogel on the curing kinetics and interfacial interaction of epoxy composites | |
Wu et al. | Water-assisted synthesis of phenolic aerogel with superior compression and thermal insulation performance enabled by thick-united nano-structure | |
Burgaz | Polyurethane Insulation Foams for Energy and Sustainability | |
US8142689B2 (en) | Fire retardancy and shape retention reinforced polyester | |
Vasquez‐Zacarias et al. | Hybrid Cellulose–Silica Materials from Renewable Secondary Raw Resources: An Eco‐friendly Method | |
Kiddell et al. | Influence of Flash Graphene on the acoustic, thermal, and mechanical performance of flexible polyurethane foam | |
Li et al. | Recycling polycarbonate wastes to prepare hydrophobic and super mechanically robust aerogels with excellent oil–water and emulsion separation performance | |
Lian et al. | Monolithic chitosan-silica composite aerogel with comprehensive performances prepared by SBG-FD method |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
121 | Ep: the epo has been informed by wipo that ep was designated in this application |
Ref document number: 22706102 Country of ref document: EP Kind code of ref document: A1 |
|
NENP | Non-entry into the national phase |
Ref country code: DE |