CN112063126B - Completely biodegradable starch composite mulching film and preparation method thereof - Google Patents
Completely biodegradable starch composite mulching film and preparation method thereof Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
- C08J5/18—Manufacture of films or sheets
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- A—HUMAN NECESSITIES
- A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
- A01G—HORTICULTURE; CULTIVATION OF VEGETABLES, FLOWERS, RICE, FRUIT, VINES, HOPS OR SEAWEED; FORESTRY; WATERING
- A01G13/00—Protecting plants
- A01G13/02—Protective coverings for plants; Coverings for the ground; Devices for laying-out or removing coverings
- A01G13/0256—Ground coverings
- A01G13/0268—Mats or sheets, e.g. nets or fabrics
- A01G13/0275—Films
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
- B29D7/00—Producing flat articles, e.g. films or sheets
- B29D7/01—Films or sheets
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2367/00—Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
- C08J2367/02—Polyesters derived from dicarboxylic acids and dihydroxy compounds
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2403/00—Characterised by the use of starch, amylose or amylopectin or of their derivatives or degradation products
- C08J2403/12—Amylose; Amylopectin; Degradation products thereof
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2405/00—Characterised by the use of polysaccharides or of their derivatives not provided for in groups C08J2401/00 or C08J2403/00
- C08J2405/04—Alginic acid; Derivatives thereof
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A40/00—Adaptation technologies in agriculture, forestry, livestock or agroalimentary production
- Y02A40/10—Adaptation technologies in agriculture, forestry, livestock or agroalimentary production in agriculture
- Y02A40/28—Adaptation technologies in agriculture, forestry, livestock or agroalimentary production in agriculture specially adapted for farming
Abstract
The application relates to the field of degradable materials, and particularly discloses a completely biodegradable starch composite mulching film and a preparation method thereof. The completely biodegradable starch composite mulching film is prepared from the following raw materials in parts by weight: 40-50 parts of poly (butylene adipate/terephthalate) resin particles, 1-2 parts of antioxidant, 1-2 parts of cross-linking agent, 3-5 parts of plasticizer and 10-15 parts of modified starch, wherein the modified starch is prepared by performing enzymolysis modification on starch particles through amylase. The completely biodegradable starch composite mulching film can be used for farmland planting, the composite mulching film adopts enzymolysis to treat starch to form starch clusters and starch short chains with cross bottoms of polymerization degrees, and after processing and pasting treatment, the bonding performance of a starch material and a resin matrix is effectively improved, and the mechanical strength of the material is improved; in addition, the preparation method of the completely biodegradable starch composite mulching film is simple and convenient in steps, and the prepared mulching film material can be completely degraded after being discarded.
Description
Technical Field
The application relates to the field of degradable materials, in particular to a completely biodegradable starch composite mulching film and a preparation method thereof.
Background
Plastic mulching films have been developed with the development of recent petroleum industry and plastic industry. Mulching is a cultivation technique for improving the growth environment of crops by an artificial method. The plastic film mulching planting not only has the functions of increasing temperature, saving water, promoting prematurity, increasing yield and the like, but also has the advantages of preventing soil loss, effectively controlling the salinity and alkalinity of the soil, reducing the leaching of nitrogen, protecting the seedlings and the roots of crops and actively promoting the growth of the crops. Most importantly, the plastic mulching cultivation increases the effective accumulated temperature by 200-300 ℃ in each growing season, and the requirement of crops on heat is met in advance. The method for covering and cultivating the crops by adopting the agricultural plastic film is one of important measures for promoting the yield increase of the crops and the agricultural modernization, and is an effective way for increasing the yield of the crops on the limited arable land area. With the development of agricultural science and technology, the use of mulching films gradually deepens into various fields of agricultural production.
The starch-based degradable mulching film generally refers to a mulching film containing starch or derivatives thereof and other degradable components in the components, and the mulching film using natural starch as a filler and using the natural starch or derivatives thereof as a blending system belongs to the category. The starch-based degradable mulching film is a large class of biodegradable plastic products, and can be classified into a biodegradable type of starch-filled polyolefin material and a completely biodegradable type of starch and biodegradable resin as main raw materials in terms of degradability.
The prior art can refer to Chinese invention patent with publication number CN1226345C, which discloses a completely biodegradable aliphatic polyester/starch composite material, the composite material comprises aliphatic polyester, starch and compatibilizer, and is characterized in that the aliphatic polyester is p-dioxanone polymer, the weight parts of each component are as follows: 30-95 parts of p-dioxanone polymer, 5-70 parts of starch and 0.1-20 parts of compatibilizer. The completely biodegradable aliphatic polyester/starch composite material can be widely used for manufacturing disposable plastic products such as agricultural mulching films, shopping bags, garbage bags, packaging materials and the like, and is a completely biodegradable aliphatic polyester/starch composite material with practical application value.
In view of the above-mentioned related arts, the inventors considered that there is a problem that the mechanical properties of the composite material are not good due to the use of too much auxiliary agent by adding a high-component compatibilizer to improve the binding property between the starch material and the resin.
Disclosure of Invention
In order to improve the bonding performance between starch and resin and the mechanical strength of the mulching film material, the application provides a completely biodegradable starch composite mulching film, which is prepared from the following raw materials in parts by weight: 40-50 parts of poly (butylene adipate/terephthalate) resin particles, 1-2 parts of antioxidant, 1-2 parts of cross-linking agent, 3-5 parts of plasticizer and 10-15 parts of modified starch, wherein the modified starch is prepared by performing enzymolysis modification on starch particles through amylase.
By adopting the technical scheme, the starch granules are subjected to enzymolysis treatment by adopting amylase, the amylase performs enzymolysis on the surfaces of the starch granules, so that the starch granules subjected to enzymolysis form a porous structure, the starch granules of the porous structure are subjected to enzymolysis treatment to form starch clusters and starch short chains with cross polymerization degrees, and a uniform short-range ordered structure is formed after gelatinization treatment, so that the bonding performance of the starch material and a resin matrix is effectively improved, and meanwhile, the degradation performance of the starch granules is effectively improved after the starch is subjected to enzymolysis treatment, so that the prepared composite material not only improves the biodegradation performance of the mulching film material, but also improves the mechanical property of the mulching film material.
Further, the modified starch is prepared by performing enzymolysis modification on starch granules by amylase and then coating and modifying the starch granules with sulfonated sodium alginate.
By adopting the technical scheme, the starch subjected to enzymolysis is coated and modified by the sulfonated modified sodium alginate, the sulfonated sodium alginate destroys the acting force among and in the sodium alginate molecules, sulfate radicals substitute the original hydroxyl positions, hydrogen bonds are correspondingly reduced, the regularity of molecular chains is reduced, the crystalline structure is changed, the amorphous area is increased, when the starch particles are coated and modified by the sulfonated sodium alginate, the sulfonated sodium alginate has the capability of forming fibers and films by chain-shaped high molecular compounds of the sulfonated sodium alginate, and interface modified parts are formed between the starch particles and the resin, so that one part is effectively entangled with the starch, the other part is effectively combined with the resin, the bonding strength of the whole mulching film material is improved, and the bonding performance between the starch and the resin is improved.
Further, the starch is corn amylose.
Through adopting above-mentioned technical scheme, because this application chooses corn amylose as raw materials, compare in traditional starch material, the intermolecular associativity, the coagulation sedimentation nature, gelatinization temperature and shearing force and the film forming ability of amylose all obtain the improvement of different degree, in addition, amylose is through the cross-linking back, and molecular weight can obtain the improvement to have stronger shearing force, film forming ability and easy coagulation sedimentation nature, the straight chain content improves, and the cross-linking effect can be better, and material mechanical properties is more excellent.
Further, the polybutylene adipate/terephthalate resin particles are C1200F type PBAT resin materials.
By adopting the technical scheme, as the C1200F PBAT resin material is adopted for preparation, in the process of biological decomposition, the C1200F PBAT resin material has more branched chain structures, loose chain arrangement and low crystallinity, and microorganisms initially permeate into an amorphous area to degrade the area, so that the C1200F PBAT resin material can be rapidly degraded and decomposed, and the biological degradation performance is improved.
Further, the preparation steps of the modified starch are as follows: (1) according to the mass ratio of 1: 2-5: 50-60, stirring and mixing p-toluenesulfonic acid, sodium alginate and N, N-dimethylformamide, placing the mixture at room temperature for homogeneous mixing, collecting mixed homogeneous liquid, stirring and mixing 4-dimethylaminopyridine and lauryl alcohol, collecting mixed liquid, placing the mixed liquid in absolute ethyl alcohol, standing and aging, collecting lower-layer precipitate, and performing dialysis treatment to obtain modified gel liquid; (2) respectively weighing the modified gel solution, glacial acetic acid, ammonium acetate, deionized water and amylase, placing the weighed modified gel solution, the glacial acetic acid, the ammonium acetate, the deionized water and the amylase in a beaker, and stirring and mixing the weighed modified gel solution, the glacial acetic acid, the ammonium acetate, the deionized water and the amylase to obtain an embedded modified gel solution; (3) respectively weighing the embedding modified gel liquid, deionized water and starch, stirring and mixing, centrifugally separating, collecting next precipitate, drying to constant weight, and collecting to obtain the modified starch.
By adopting the technical scheme, the starch subjected to enzymolysis is coated and modified by the sodium alginate modified by sulfonation, the acting force between the sodium alginate molecules and the acting force in the sodium alginate molecules are destroyed by the sodium alginate after sulfonation, and when the sodium alginate is coated and modified on the starch particles, an interface modified part is formed between the starch particles and the resin, so that one part is effectively intertwined with the starch, the other part is effectively combined with the resin, the bonding strength of the whole material is improved, and the bonding performance between the starch and the resin is improved.
Further, the amylase is preferably isoamylase.
By adopting the technical scheme, because the isoamylase is adopted for enzymolysis, the isoamylase only acts on alpha-1, 6 glycosidic bond of the amylopectin, the amorphous area mainly consists of the amylopectin, so the amorphous area is preferentially subjected to enzymolysis, and the crystalline part of the starch granule structure mainly consists of the amylose to form a protective barrier for the enzymolysis of the amorphous area, so a pore structure can be formed on the surface of the amylose granule, thereby improving the binding performance between the resin matrix and the starch granule.
Further, the molecular weight of the modified gel liquid is 3500 daltons.
By adopting the technical scheme, because the gel liquid with low molecular weight is adopted for modification, the formed coating structure can effectively improve the degradation rate of the material during biodegradation and shorten the biodegradation time.
In a second aspect, the application provides a preparation method of a completely biodegradable starch composite mulching film, which comprises the following specific preparation steps: s1, stirring and mixing the polybutylene adipate/terephthalate resin particles, the antioxidant, the cross-linking agent, the plasticizer and the modified starch according to the formula components, and collecting a mixture; s2, placing the mixture in an extruder, extruding, granulating and blow-molding; s3, cutting and packaging to obtain the completely biodegradable starch composite mulching film.
By adopting the technical scheme, the composite mulching film material is prepared by extruding and blowing the film after the mixing treatment of the extruder, the whole scheme is simple, the steps are convenient, the production cost can be effectively reduced, the production efficiency is improved, and the prepared mulching film material can be completely biodegraded after being discarded.
Further, in the step S3, the plastication treatment temperature is 165-175 ℃.
By adopting the technical scheme, due to the adoption of the proper mixing treatment temperature, the starch granules and the resin granules are effectively mixed and co-extruded to form a blending system, and meanwhile, the starch granules can effectively carry out gelatinization reaction in the temperature range, so that the bonding performance between the matrix resin and the starch granules is effectively improved, and the bonding performance between the starch and the resin is further improved.
In summary, the present application includes at least one of the following beneficial technical effects:
firstly, in the application, modified sodium alginate is sulfonated and then coated on the surface of enzymolyzed amylose, amylase forms a porous structure on the surface of starch granules after the enzymolysis treatment of the amylose, the amylose granules with the porous structure are enzymolyzed to form starch clusters and starch short chains crossing the polymerization degree, and then coated and connected with the sulfonated sodium alginate, and through a chain-shaped high molecular compound of the sulfonated sodium alginate, the sulfonated sodium alginate has the capacity of forming fibers and films, and an interface modified part is formed between the starch granules and resin, so that one part is effectively intertwined with the starch, the other part is effectively combined with the resin, the combination strength of the mulching film material is improved, and the combination performance between the starch and the resin is improved.
Secondly, the C1200F PBAT resin material is adopted for preparation, and in the process of biological decomposition, the C1200F PBAT resin material has more branched chain structures, loose chain arrangement and low crystallinity, and microorganisms initially permeate into an amorphous area to degrade the area, so that the C1200F PBAT resin material can be rapidly degraded and decomposed, and the biological degradation performance is improved.
And thirdly, the method adopts an extruder to perform mixing treatment and then extrude and blow the film to prepare the composite mulching film material, selects a proper plastication treatment temperature to effectively mix and co-extrude the starch particles and the resin particles to form a blending system, and simultaneously, the starch particles can effectively perform gelatinization reaction within the temperature range, so that the bonding performance between matrix resin and the starch particles is effectively improved, the bonding performance between the starch and the resin is further improved, the overall preparation method is simple, the steps are convenient, the production cost can be effectively reduced, and the production efficiency is improved.
Detailed Description
The present application will be described in further detail with reference to examples.
In the examples of the present application, the following instruments and apparatuses are used, but not limited thereto:
the device comprises the following steps: an electric heating air blowing drying box, an SHR-10 high-speed mixer, an SJL-160 two-roll plasticator, a 63 TZLB-D four-column flat vulcanizing machine, a CMT5105 electronic universal tensile testing machine and an XJU-5.5 cantilever beam impact testing machine.
Examples
Example 1
S1, mixing the components in a mass ratio of 1: 2: 50, stirring and mixing p-toluenesulfonic acid, sodium alginate and N, N-dimethylformamide, placing the mixture at room temperature for homogenizing and mixing for 10min, and collecting a mixed homogenized solution; stirring and mixing 4-dimethylaminopyridine and lauryl alcohol according to the mass ratio of 1:10, preserving heat at 40 ℃ for 1h, collecting mixed liquor, placing the mixed liquor into absolute ethyl alcohol, standing and aging, collecting lower-layer precipitates, dissolving the precipitates with deionized water, placing the precipitates into a 3500 molecular weight dialysis bag for dialysis treatment for 100h, and collecting dialysate to obtain modified gel liquid;
s2, respectively weighing 45 parts of modified gel liquid, 3 parts of glacial acetic acid, 0.5 part of ammonium acetate, 35 parts of deionized water and 3 parts of isoamylase in parts by weight, placing the materials in a beaker, and stirring and mixing the materials for 10min to obtain embedded modified gel liquid;
s3, respectively weighing 45 parts of embedding modified gel liquid, 55 parts of deionized water and 15 parts of corn amylose according to parts by weight, carrying out heat preservation and stirring mixing at 30 ℃ for 1 hour, carrying out centrifugal separation, collecting next precipitate, drying at 100 ℃ to constant weight, and collecting modified corn amylose;
s4, respectively weighing 40 parts of poly (butylene adipate/terephthalate) resin particles, 1 part of antioxidant, 1 part of cross-linking agent, 3 parts of plasticizer and 10 parts of modified corn amylose in parts by weight, placing the materials in an extruder, controlling the plastication temperature to be 165 ℃, and performing extrusion treatment and blow molding to obtain the completely biodegradable starch composite mulching film.
Example 2
S1, mixing the raw materials in a mass ratio of 1: 2: 50, stirring and mixing p-toluenesulfonic acid, sodium alginate and N, N-dimethylformamide, placing the mixture at room temperature for homogenizing and mixing for 12min, and collecting a mixed homogenized solution; stirring and mixing 4-dimethylaminopyridine and lauryl alcohol according to the mass ratio of 1:10, preserving heat at 45 ℃ for 1h, collecting mixed liquor, placing the mixed liquor into absolute ethyl alcohol, standing and aging, collecting lower-layer precipitates, dissolving the precipitates with deionized water, placing the precipitates into a 3500 molecular weight dialysis bag for dialysis treatment for 110h, and collecting dialysate to obtain modified gel liquid;
s2, respectively weighing 47 parts of modified gel liquid, 4 parts of glacial acetic acid, 0.7 part of ammonium acetate, 37 parts of deionized water and 4 parts of isoamylase by weight, placing the materials in a beaker, and stirring and mixing for 12min to obtain embedded modified gel liquid;
s3, respectively weighing 47 parts of embedding modified gel liquid, 57 parts of deionized water and 17 parts of corn amylose according to parts by weight, carrying out heat preservation and stirring mixing at 32 ℃, carrying out centrifugal separation, collecting next precipitate, drying at 105 ℃ to constant weight, and collecting modified corn amylose;
s4, respectively weighing 47 parts of poly (butylene adipate/terephthalate) resin particles, 1 part of antioxidant, 2 parts of cross-linking agent, 4 parts of plasticizer and 12 parts of modified corn amylose in parts by weight, placing the materials into an extruder, controlling the plastication temperature to be 170 ℃, and performing extrusion treatment and blow molding to obtain the completely biodegradable starch composite mulching film.
Example 3
S1, mixing the components in a mass ratio of 1: 2: 50, stirring and mixing p-toluenesulfonic acid, sodium alginate and N, N-dimethylformamide, homogenizing and mixing for 15min at room temperature, and collecting a mixed homogeneous solution; stirring and mixing 4-dimethylaminopyridine and lauryl alcohol according to the mass ratio of 1:10, preserving heat at 50 ℃ for 2 hours, collecting mixed liquor, placing the mixed liquor into absolute ethyl alcohol, standing and aging, collecting lower-layer precipitates, dissolving the precipitates with deionized water, placing the precipitates into a 3500 molecular weight dialysis bag for dialysis treatment for 120 hours, and collecting dialysate to obtain modified gel liquid;
s2, respectively weighing 50 parts of modified gel liquid, 5 parts of glacial acetic acid, 1.0 part of ammonium acetate, 40 parts of deionized water and 5 parts of isoamylase in parts by weight, placing the materials in a beaker, and stirring and mixing the materials for 15min to obtain embedded modified gel liquid;
s3, respectively weighing 50 parts of embedded modified gel liquid, 60 parts of deionized water and 20 parts of corn amylose according to parts by weight, carrying out heat preservation and stirring mixing at 35 ℃ for 2 hours, carrying out centrifugal separation, collecting next precipitate, drying at 110 ℃ to constant weight, and collecting modified corn amylose;
s4, respectively weighing 50 parts of poly (butylene adipate/terephthalate) resin particles, 2 parts of antioxidant, 2 parts of cross-linking agent, 5 parts of plasticizer and 15 parts of modified corn amylose in parts by weight, placing the materials into an extruder, controlling the plastication temperature to be 175 ℃, and performing extrusion treatment and blow molding to obtain the completely biodegradable starch composite mulching film.
Examples 4 to 5
The dialysis bags used in step S1 of the completely biodegradable starch composite mulching films of examples 4 to 5 were different in molecular weight from the dialysis bag used in example 1, and the remaining conditions and component ratios were the same as those in example 1, as shown in table 1.
TABLE 1 molecular weights of dialysis bags in examples 1-5
The performance tests of examples 1 to 7 were performed to specifically test the mechanical properties and biodegradability of the completely biodegradable starch composite mulch material prepared.
Detection method/test method
The tensile property is tested according to GB/T1040-2006, and the tensile rate is 50 mm/min;
the impact performance is tested according to GB/T1843-2008, and the residual width at the bottom of the notch of the sample is 8 mm;
the biodegradation performance is that a sample to be tested is used as a carbon source and an energy source, a single strain (Aspergillus niger) and a composite strain (soil suspension) are respectively inoculated, the growth rate of specific microorganisms on the surface of the film after 14 days is observed, and the growth rate can be divided into 5 grades:
the 0 grade is that no visible microorganism grows on the surface of the sample;
grade 1 is less than or equal to 10% of the sample surface showing microbial growth;
grade 2 is 10% -30% of the sample surface showing microbial growth;
grade 3 is 30% -60% of the sample surface showing microbial growth;
the sample surface at level 4 of 60% to 100% showed microbial growth.
The specific detection results are shown in table 2 below:
TABLE 2 Performance test Table
Referring to the comparison of the performance tests of table 2, it can be found that:
the performance comparison of the examples 1 to 3 shows that the mechanical property of the example 3 is the best, because the proportion of the added materials in the example 3 is the highest, which shows that the technical scheme of the application can be implemented.
Comparing the performances of example 1 with those of example 4 and example 5, since the dialysis molecular weight used in example 5 is higher than that of example 1 and example 4, the mechanical property of the sulfonated sodium alginate is higher than that of the sulfonated sodium alginate in examples 1 and 4, which shows that the sulfonated sodium alginate chain polymer compound has the capability of forming fibers and films, an interface modification part is formed between the starch granules and the resin, so that one part is effectively entangled with the starch, the other part is effectively combined with the resin, the bonding strength of the whole material is improved, the bonding performance between the starch and the resin is improved, on the basis, the biodegradation performance of the embodiment 4 and the embodiment 5 is poorer than that of the embodiment 1, which shows that the degradation rate of the material in the biodegradation process can be effectively improved and the biodegradation time can be shortened only by adopting the low-molecular-weight gel liquid for modification.
Comparative example
Comparative examples 1 to 6
Comparative examples 1-6 were prepared using unmodified starch instead of modified starch, and the remaining components were the same as in example 1, as shown in Table 3.
Table 3 raw material composition of the completely biodegradable starch composite mulching film in comparative examples 1 to 6
Comparative examples 7 to 10
Comparative examples 7-10 were prepared using pure corn starch instead of corn amylose, and the remaining components were the same as in example 1, specifically shown in table 4.
TABLE 4 raw material composition of the completely biodegradable starch composite mulch film in comparative examples 7-10
| Weight/kg | Comparative example 7 | Comparative example 8 | Comparative example 9 | Comparative example 10 |
| PBAT resin pellets | 40 | 40 | 40 | 40 |
| Antioxidant agent | 1 | 1 | 1 | 1 |
| Crosslinking agent | 1 | 1 | 1 | 1 |
| Modified pure corn starch | 10 | 12 | 13 | 15 |
| Plasticizer | 3 | 3 | 3 | 3 |
Comparative examples 11 to 15
Comparative examples 11-15 were prepared using equal masses of PE instead of PBAT resin material, with the remaining components being the same as in example 1, as shown in table 5.
TABLE 5 raw material composition of starch composite mulch film capable of complete biodegradation in comparative examples 11-15
And (3) respectively carrying out performance tests on the comparative examples 1-15 by a performance detection test, and specifically testing the mechanical property and the biodegradation property of the prepared completely biodegradable starch composite mulching film material.
Detection method/test method
The tensile property is tested according to GB/T1040-2006, and the tensile rate is 50 mm/min;
the impact performance is tested according to GB/T1843-2008, and the residual width at the bottom of the notch of the sample is 8 mm;
the biodegradation performance is that a sample to be tested is used as a carbon source and an energy source, a single strain (Aspergillus niger) and a composite strain (soil suspension) are respectively inoculated, the growth rate of specific microorganisms on the surface of the film after 14 days is observed, and the growth rate can be divided into 5 grades:
level 0 is no visible microorganism growth on the surface of the sample;
grade 1 is less than or equal to 10% of the sample surface showing microbial growth;
grade 2 is 10% -30% of the sample surface showing microbial growth;
grade 3 is 30% -60% of the sample surface showing microbial growth;
grade 4 is 60% -100% of the sample surface showing microbial growth.
The specific test results are shown in table 6 below:
TABLE 6 Performance test Table
Referring to the comparison of the performance tests in table 6, it can be found that:
comparing the performances of the comparative examples 1-6 with the performances of the example 1, the mechanical property and the biodegradability of the comparative example are reduced because the comparative example is prepared by adopting unmodified starch granules, which shows that the combination property of the starch material and the resin matrix is effectively improved, the biodegradability is improved, and the mechanical strength of the mulching film material is also improved by adopting amylase to carry out enzymolysis treatment on the starch granules.
Comparing the performances of the comparative examples 7-10 with those of the example 1, because the comparative examples adopt common starch granules instead of amylose, the mechanical properties of the starch granules are reduced, because the amylose has higher performance, stronger shearing force, film forming property and easy coagulability compared with the traditional starch material, and simultaneously, the amylose content is improved, the crosslinking effect is better, and the mechanical properties of the material are more excellent.
Finally, comparing the performances of the comparative examples 11 to 15 with the example 1, the mechanical properties of the comparative examples are significantly improved due to the preparation of the PE resin, but the degradability of the PBAT resin is poor, because the PBAT resin material adopted in the application has more branched structures, and microorganisms initially permeate into an amorphous area to degrade the area, the PBAT resin material can be rapidly degraded and decomposed, and the biodegradability is improved.
The present embodiment is only for explaining the present application, and it is not limited to the present application, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present application.
Claims (3)
1. The completely biodegradable starch composite mulching film is characterized by being prepared from the following raw materials in parts by weight:
40-50 parts of poly (butylene adipate/terephthalate) resin particles;
1-2 parts of an antioxidant;
1-2 parts of a crosslinking agent;
3-5 parts of a plasticizer;
10-15 parts of modified starch;
the starch is corn amylose;
the polybutylene adipate/terephthalate resin particles are C1200F type PBAT resin materials;
the preparation steps of the modified starch are as follows:
(1) according to the mass ratio of 1: 2-5: 50-60, stirring and mixing p-toluenesulfonic acid, sodium alginate and N, N-dimethylformamide, placing the mixture at room temperature for homogeneous mixing, collecting mixed homogeneous liquid, stirring and mixing 4-dimethylaminopyridine and lauryl alcohol, collecting mixed liquid, placing the mixed liquid in absolute ethyl alcohol, standing and aging, collecting lower-layer precipitate, and performing dialysis treatment to obtain modified gel liquid;
(2) respectively weighing the modified gel solution, glacial acetic acid, ammonium acetate, deionized water and amylase, placing the weighed modified gel solution, the glacial acetic acid, the ammonium acetate, the deionized water and the amylase in a beaker, and stirring and mixing the weighed modified gel solution, the glacial acetic acid, the ammonium acetate, the deionized water and the amylase to obtain an embedded modified gel solution;
(3) respectively weighing the embedding modified gel liquid, deionized water and starch, stirring and mixing, centrifugally separating, collecting next precipitate, drying to constant weight, and collecting to obtain modified starch;
the amylase is isoamylase;
the molecular weight of the modified gel liquid is 3500 Dalton.
2. The preparation method of the completely biodegradable starch composite mulching film according to claim 1, is characterized by comprising the following specific preparation steps:
s1, stirring and mixing the polybutylene adipate/terephthalate resin particles, the antioxidant, the cross-linking agent, the plasticizer and the modified starch according to the formula components, and collecting a mixture;
s2, placing the mixture in an extruder, extruding, granulating and blow-molding;
s3, cutting and packaging to obtain the completely biodegradable starch composite mulching film.
3. The preparation method of the completely biodegradable starch composite mulching film according to claim 2, wherein the temperature of the extrusion granulation in the step S2 is 165-175 ℃.
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