CN112876899A - Method for reducing volume shrinkage of photocuring coating by using hollow/porous elastic microspheres - Google Patents
Method for reducing volume shrinkage of photocuring coating by using hollow/porous elastic microspheres Download PDFInfo
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Abstract
The invention discloses application of elastic hollow/porous microspheres in a coating, and particularly relates to a coating containing the elastic hollow/porous microspheres and prepared by adding the elastic hollow/porous microspheres in the coating, so that the curing volume shrinkage of the coating is reduced. According to the shrinkage test of a linear laser confocal method, the curing volume shrinkage of the coating containing the elastic hollow/porous microspheres is reduced by 30-65%, and the elastic hollow/porous microspheres are 0.5-2.5 wt% of the total mass of the matrix resin and the monomers. The invention uses the modified silicon dioxide particles as the emulsifier, thus improving the compatibility of the elastic hollow/porous microspheres in the coating; the elastic hollow/porous microspheres are used for reducing the volume shrinkage of the photocuring coating, only microspheres with the content of about 1.5 wt% are added, the volume shrinkage of the cured material is reduced, and the excellent comprehensive performance of the coating is maintained.
Description
Technical Field
The invention belongs to the technical field of photocuring coatings, and particularly relates to a method for reducing volume shrinkage of a photocuring coating by using hollow/porous elastic microspheres.
Background
The photocuring technology has the advantages of high efficiency, energy conservation, environmental protection, economy, wide applicability and the like, but the biggest problem limiting the application of the photocuring technology is that the photocuring technology generates larger volume shrinkage after polymerization. The fundamental reason for this is that the change in intermolecular spacing on a microscopic scale results in a change in volume on a macroscopic scale, as the intermolecular monomer molecules are converted from remote van der waals interactions to covalent interactions before and after the reaction. The volume shrinkage of a general photocuring system is between 5 and 15 percent, and the molding precision, the performance and the service life of the material are seriously influenced by the larger volume shrinkage. Therefore, it is important to reduce the volume shrinkage of the photocurable system.
The prior method for reducing the shrinkage rate comprises the following steps: (1) reducing the concentration of reactive functional groups, such as: adding filler to synthesize a novel monomer with a rigid or flexible chain segment; (2) extending stress relaxation times, such as: introducing a chain transfer agent; (3) volume to compensate for shrinkage, such as: synthesis of swelling monomers or hybrid polymerization. The current common method is to introduce a filler or a chain transfer agent into a photocuring system, but the addition amount of the filler or the chain transfer agent is generally more than 10%, sometimes even more than 50%, and although the volume shrinkage rate is improved, the comprehensive mechanical property of the material is greatly reduced, so that the application of the material is seriously influenced.
The elastic hollow/porous microsphere is widely applied to the fields of biology, medicine, materials and the like due to unique physical and chemical properties. In the field of coatings, the elastic hollow/porous microspheres can be used for isolating heat transfer to prepare a heat-insulating coating; in the medical field, it is often used as a drug carrier.
Disclosure of Invention
In order to solve the problems, maintain the mechanical property of the coating and reduce the curing volume shrinkage rate, the invention prepares a special elastic hollow/porous microsphere, utilizes the internal cavity/porous structure to effectively resist the internal stress generated by polymerization and prolong the release time of the polymerization stress; the result shows that the volume shrinkage of the light-cured resin can be greatly reduced under the condition of less (less than 5 wt%) adding amount of the microspheres, and the basic mechanical property of the cured material is kept unchanged or improved.
The invention aims to provide application of elastic hollow/porous microspheres in a coating, in particular to a method for reducing the volume shrinkage of a photocuring coating by utilizing the elastic hollow/porous microspheres, wherein the curing volume shrinkage of the coating with the same formula is greatly reduced by 30-65% before and after the elastic hollow/porous microspheres are added.
Further, the cured volume shrinkage of the coating comprising the elastic hollow/porous microspheres was reduced by 60 ± 5% by a linear confocal laser polymerization shrinkage test.
Further, the volume shrinkage is measured by using the principle of linear confocal measurement: coupling a 3D line scanning laser confocal instrument with an ultraviolet point light source Omicure S2000, dripping a sample on a polypropylene plastic plate, scanning in real time, and finally obtaining the change of the sample volume, wherein the calculation method of the volume shrinkage rate delta V comprises the following steps:
wherein, VENDVolume after curing, VSTARTIs the volume before curing.
In order to achieve the above object, another object of the present invention is to provide a method for preparing elastic hollow/porous microspheres by Pickering emulsion method, wherein the specific preparation scheme is as follows:
(1) firstly, synthesizing silicon dioxide nano particles by a sol-gel method, placing 2.8mL of deionized water, 150mL of absolute ethyl alcohol and 9.7mL of ammonia water in a single-neck flask, heating to 60 ℃, starting magnetic stirring, and stirring at the speed of 300 rmp. 4mL of TEOS (tetraethyl orthosilicate) is slowly added into the mixed solution in a dropwise manner, and SiO is obtained after 6 hours of reaction2And (3) dispersing the mixture.
(2) SiO to the above step (1)2200 mu L of silane coupling agent MPS is dripped into the dispersion liquid to react for 19 hours at normal temperature, and the stirring speed is 300 rmp. After the reaction is finished, SiO is obtained2Washing MPS dispersion liquid with ethanol for three times, centrifuging, drying in a vacuum oven to obtain double bond modified SiO2And (3) nanoparticles.
(3) Respectively preparing water phase and oil phase. The formula of the oil phase is respectively as follows: 55% by weight of GBL (butyrolactone), 21% by weight of GMA (glycidyl methacrylate), 21% by weight of PUA (urethane acrylate)) 3 wt% 1173 (photoinitiator), and the modified SiO prepared in step (2) above2Nanoparticles in an amount of 5 wt%. The aqueous phase solution consisted of a 1 wt% aqueous solution of polyvinyl alcohol (PVA).
(4) Measuring 1mL of the oil phase in the step (3), and dropwise adding 10mL of the water phase in the step (3). Emulsifying for 2min at a shear rate of 20krmp by a high-speed disperser to prepare the Pickering emulsion.
(5) Immediately illuminating the Pickering emulsion prepared in the step (4) under a 365nm LED lamp, wherein the light intensity is 30mw/cm2The irradiation time was 5 min. And washing and centrifuging by using ethanol, and then drying in a vacuum oven to prepare the porous hollow microspheres. The microspheres have an average particle diameter of 1 to 100. mu.m, preferably 5 to 50 μm, particularly preferably 10 to 30 μm, as measured by laser diffraction.
Another object of the present invention is to provide a method for preparing a coating layer comprising elastic hollow/porous microspheres, wherein the elastic porous microspheres are 0.5 to 2.5 wt% of the total mass of a matrix resin and a reactive diluent in the coating layer.
In general, the volume shrinkage is reduced after the addition of the inert filler, but the reduction ratio is the same as the ratio of the filler; large amounts of inert fillers are usually added to reduce the volume shrinkage. In the invention, the volume shrinkage rate can be greatly reduced by adding a small amount of the elastic hollow/porous microspheres. The elastic hollow/porous microspheres used in the invention have certain deformability, and the deformability can offset volume shrinkage, so that the effect of reducing the volume shrinkage rate is achieved.
The surface of the elastic hollow/porous microsphere used in the invention has decorated active reaction sites, namely, the silicon dioxide nano particles with double bonds. The silicon dioxide nano particles with double bonds can increase the compatibility of the elastic hollow/porous microspheres and a resin system on one hand; on the other hand, after the elastic hollow/porous microspheres are successfully prepared, the double bonds still have activity and can participate in the curing of the coating, so that the overall performance of the coating is improved/unchanged. That is, the double-bond modified silica nanoparticles enhance the surface bonding force between the resin and the microspheres, improve the compatibility between the resin phase and the filler phase, and prevent the mechanical properties of the resin matrix from being affected by the gaps generated between the microspheres and the resin. Therefore, the elastic hollow/porous microspheres used in the invention have good compatibility with a coating resin system, and can be blended with the resin system; during the blending process, the shell layer of the microsphere is not damaged.
Further, the elastic hollow/porous microspheres used in the present invention have one or more cavities, and the total volume of the cavities accounts for 10% to 90%, preferably 30% to 70%, more preferably 40% to 60%, and most preferably 50% of the volume of the microsphere.
Furthermore, the shell of the elastic hollow/porous microsphere used in the invention can be a simple polymer shell or a hybrid shell of polymer and inorganic particles.
Further, the method for preparing the coating containing the elastic hollow/porous microspheres specifically comprises the following steps: weighing matrix resin and an active diluent, uniformly mixing, adding a photoinitiator 1173 and elastic hollow/porous elastic microspheres, wherein the elastic porous microspheres are 0.5-2.5 wt% of the total mass of the matrix resin and the active diluent, and stirring a sample at a stirring speed of 200-350rmp for 4-8h, preferably at a stirring speed of 300rmp for 6h under a photophobic condition; and removing air bubbles in the vacuum oven, coating and carrying out photocuring to obtain the photocuring coating.
Further, as a preferred embodiment, the matrix resin includes any one of epoxy acrylic resin, urethane acrylic resin, polyester acrylic resin, and the like; the reactive diluent includes any one of a monofunctional reactive diluent, a difunctional reactive diluent, a trifunctional reactive diluent, a polyfunctional reactive diluent, and the like. Preferably, the base resin is EA (bisphenol A type epoxy acrylate), the reactive diluent is TPGDA (tripropylene glycol diacrylate) and the photoinitiator is 1173 (2-hydroxy-2-methyl-1-phenyl-1-propanone).
Compared with the prior art, the invention has the characteristics and beneficial effects that:
(1) the invention uses the modified silicon dioxide particles as the emulsifier, and improves the compatibility of the hollow/porous microspheres in the coating.
(2) The invention utilizes the porous elastic microspheres to reduce the volume shrinkage of the photocuring coating, and compared with the prior art, the addition amount of the porous elastic microspheres is greatly reduced. Only microspheres with the content of about 1.5 wt% are added, so that the reaction rate can be effectively prolonged, and the volume shrinkage of the cured coating film can be greatly reduced.
(3) The invention utilizes the porous microspheres to reduce the volume shrinkage of the coating and keeps the excellent comprehensive performance of the coating.
Drawings
FIG. 1 is a diagram of the topography of a microsphere scanning electron microscope;
FIG. 2 is a scanning electron microscope characterization of microspheres after grinding;
FIG. 3 is a graph of shrinkage stress as a function of time;
FIG. 4 is a cross-sectional view of the laser confocal method of measuring volume shrinkage of example 1; the black line represents the cross-sectional view of the sample before curing; the red line represents the cross-sectional view of the sample after the real-time solidification is finished after the solidification;
FIG. 5 is a cross-sectional view of the laser confocal method of volume shrinkage measurement in example 4; the black line represents the cross-sectional view of the sample before curing; the red line represents the cross-sectional view of the sample after the end of the real-time curing after curing.
Detailed Description
The invention is further described with reference to the following figures and examples.
Examples
The present invention will be better understood from the following examples. However, those skilled in the art will readily appreciate that the specific material ratios, process conditions and results thereof described in the examples are illustrative only and should not be taken as limiting the invention as detailed in the claims.
In order to make the objects, technical solutions and advantages of the present invention more apparent, the following examples are further detailed. It will be appreciated by those skilled in the art that the examples described are only for the purpose of facilitating an understanding of the invention and are not intended to be limiting.
In order to optimize the scheme, the system of the invention discusses the influence of the content of the elastic hollow/porous microspheres on the reduction of the shrinkage of the coating under the condition that the addition amount is 0.5-2.5 wt% of the total mass of the matrix resin and the monomer. The specific method for preparing the coating containing the elastic hollow/porous microspheres comprises the following steps:
the elastic porous microspheres are added into an EA-TPGDA coating formula according to the content of 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt% and 2.5 wt% of the total mass of the matrix resin and the monomer respectively, and the coating preferably comprises the following components in parts by weight:
then, the following methods were respectively employed to test the effects of the present invention:
(1) basic properties of the cured film: the basic properties of the cured films were tested using an aluminum plate as the substrate for the coating film.
Thickness: measuring by using a German Qnix 1500 coating thickness gauge, and performing multiple tests to obtain an average value;
pencil hardness: the pencil hardness of the cured film was determined manually using a BYK dolly pencil hardness meter according to the standard GB/T6739-;
hardness of the swing rod: carrying out a swing rod damping test by adopting a BYK swing rod hardness instrument according to a standard GB/T1730 + 1993 to determine the swing rod hardness(s) of the cured film;
adhesion force: according to the standard GB/T9286-1998, ISO2409-72, a QFH coating grid cutting instrument is used for testing, and the adhesion of the cured film is judged according to the damage level of the grid cutting coating;
gloss: testing by adopting a BYK gloss meter according to a GB/T9754-2007 testing method;
(2) dynamic thermomechanical analysis (DMA) samples were prepared as rectangular bars of 65mm by 3.21mm by 2.79mm gauge using a Teflon die, and the length, width and thickness of the same bar were averaged at three different locations. And selecting a double-cantilever beam mode to test the dynamic mechanical properties of the sample strips. The test temperature is 30 ℃ to 250 ℃, the temperature is raised at the rate of 3 ℃/min, the frequency is 1Hz, the strain is 0.1 percent, and the test is carried out according to the correct operation of the instrument.
(3) And (3) testing the tensile property, namely preparing the sample into a dumbbell-shaped sample bar by using a polytetrafluoroethylene die, wherein the middle size of the tensile sample bar is 16mm multiplied by 3.7mm multiplied by 2 mm. The tensile properties of the test specimens were measured according to ASTM D412-D using an Instron 5967 tensile tester at a tensile rate of 10mm/min and the average value was determined several times at room temperature.
(4) And (3) testing the double bond conversion rate and the real-time rheological property, namely coupling a rotational rheometer Mars 60 and an ultraviolet point light source Omicure S2000 to monitor the change of the axial shrinkage stress, the material modulus and the double bond conversion rate in the polymerization process in real time. The test is carried out in a mode of controlling strain by a rheometer, the strain value is 1 percent, the thickness of a sample is 0.3mm, the diameter of the sample is 20mm, and the test light intensity is 1mw/cm2The test time is 300s, the ultraviolet mercury lamp is started at 50s, and the collection interval is 4 s. Meanwhile, the exposure sample is continuously scanned by using a total reflection infrared platform, and the distance of 1396cm is measured by acrylic double bonds-1～1422cm-1The double bond conversion was calculated from the change in area of the peak. The same sample was tested in duplicate 3 times and the results averaged.
(5) Measurement of volume shrinkage: the test was performed using the principle of linear confocal. The method comprises the steps of coupling a 3D line scanning laser confocal instrument of an LMI company with an ultraviolet point light source Omicure S2000, dropwise adding 50 mu L of a sample on a polypropylene plastic plate, carrying out real-time scanning, wherein the testing time is 300S, the collection interval is 7S, and finally obtaining the volume change of the sample. The volume shrinkage (DeltaV) is expressed by
VENDVolume after curing, VSTARTIs the volume before curing. The test was repeated 3 times and the average was taken.
Example 1: without adding porous elastic microspheres
1. Weighing 10gEA (bisphenol A epoxy acrylate EA, 10g TPGDA (tripropylene glycol diacrylate) according to the mass ratio of 1:1, uniformly mixing, adding 0.1g of photoinitiator 1173 (2-hydroxy-2-methyl-1-phenyl-1-acetone), and stirring the sample for 6 hours in a dark place at the stirring speed of 300 rmp.
2. Putting the sample into a vacuum oven, removing bubbles, pouring a small amount of sample into a mold, and curing by using a crawler-type photocuring machine to prepare a tensile sample strip and a dynamic thermal analysis test sample strip; and taking a small amount of samples to coat on an aluminum plate, and curing by using a crawler-type photocuring machine to obtain the photocuring coating.
3. And respectively carrying out coating performance, mechanical property and infrared-rheological combined test on the material.
Example 2: adding 0.1g of elastic hollow/porous microspheres
1. Preparing modified silicon dioxide nano particles:
(1-1) firstly synthesizing silicon dioxide nanoparticles by a sol-gel method, placing 2.8mL of deionized water, 150mL of absolute ethyl alcohol and 9.7mL of ammonia water in a single-neck flask, heating to 60 ℃, starting magnetic stirring, wherein the stirring speed is 300 rmp; 4mL of TEOS (tetraethyl orthosilicate) is slowly added into the mixed solution in a dropwise manner, and SiO is obtained after 6 hours of reaction2And (3) dispersing the mixture.
(1-2) SiO in the above step (1-1)2200 mu L of silane coupling agent MPS is dripped into the dispersion liquid to react for 19 hours at normal temperature, and the stirring speed is 300 rmp. After the reaction is finished, SiO is obtained2And washing and centrifuging the MPS dispersion liquid for three times by using ethanol, and then putting the MPS dispersion liquid into a vacuum oven for drying to finally obtain the SiO2 nano-particles with double bond modification.
2. Preparing elastic hollow/porous microspheres:
(2-1) preparing porous microspheres by a Pickering emulsion method, and respectively preparing a water phase and an oil phase. The formula of the oil phase is respectively as follows: 55 wt% GBL (butyrolactone), 21 wt% GMA (glycidyl methacrylate), 21 wt% PUA (urethane acrylate), 3 wt% 1173 (photoinitiator), and the modified SiO prepared in the above step (2)2Nanoparticles in an amount of 5 wt%. The aqueous phase solution consisted of a 1 wt% aqueous solution of PVA (polyvinyl alcohol).
(2-2) measuring 1mL of the oil phase in the step (2-1), and dropwise adding 10mL of the water phase in the step (3). Emulsifying for 2min at a shear rate of 20krmp by a high-speed disperser to prepare the Pickering emulsion.
(2-3) immediately illuminating the Pickering emulsion prepared in the step (2-2) under a 365nm LED lamp, wherein the light intensity is 30mw/cm2The irradiation time was 5 min. And washing and centrifuging by using ethanol, and then drying in a vacuum oven to prepare the porous hollow microspheres. The microspheres had an average particle size of 22.5 μm as measured by laser diffraction.
3. Weighing 10g of EA (bisphenol A type epoxy acrylate) and 10g of TPGDA (tripropylene glycol diacrylate) according to the mass ratio of 1:1, uniformly mixing, adding 0.1g of photoinitiator 1173 (2-hydroxy-2-methyl-1-phenyl-1-acetone), adding 0.1g of porous elastic microspheres prepared in the step 2, and stirring the sample for 6 hours in a dark place at the stirring speed of 300 rpm.
4. Putting the sample into a vacuum oven, removing bubbles, pouring a small amount of sample into a mold, and curing by using a crawler-type photocuring machine to prepare a tensile sample strip and a dynamic thermal analysis test sample strip; and taking a small amount of samples to coat on an aluminum plate, and curing by using a crawler-type photocuring machine to obtain the photocuring coating.
5. The material is respectively subjected to coating performance, mechanical property, double bond conversion rate, rheology, test and volume shrinkage test.
Example 3: 0.2g of porous elastic microspheres were added
1. Preparing modified silicon dioxide nano particles:
the preparation method is the same as the above example 2
2. Preparing porous elastic microspheres:
the preparation method is the same as the above example 2
3. Weighing 10g of EA (bisphenol A type epoxy acrylate) and 10g of TPGDA (tripropylene glycol diacrylate) according to the mass ratio of 1:1, uniformly mixing, adding 0.1g of photoinitiator 1173 (2-hydroxy-2-methyl-1-phenyl-1-acetone), adding 0.2g of the porous elastic microspheres prepared in the step 2, and stirring the sample for 6 hours in the dark at the stirring speed of 300 rpm.
4. Putting the sample into a vacuum oven, removing bubbles, pouring a small amount of sample into a mold, and curing by using a crawler-type photocuring machine to prepare a tensile sample strip and a dynamic thermal analysis test sample strip; and taking a small amount of samples to coat on an aluminum plate, and curing by using a crawler-type photocuring machine to obtain the photocuring coating.
5. And respectively carrying out coating performance, mechanical property and infrared-rheological combined test on the material.
Example 4: 0.3g of porous elastic microspheres were added
1. Preparing modified silicon dioxide nano particles:
the preparation method is the same as the above example 2
2. Preparing porous elastic microspheres:
the preparation method is the same as the above example 2
3. Weighing 10g of EA (bisphenol A type epoxy acrylate) and 10g of TPGDA (tripropylene glycol diacrylate) according to the mass ratio of 1:1, uniformly mixing, adding 0.1g of photoinitiator 1173 (2-hydroxy-2-methyl-1-phenyl-1-acetone), adding 0.3g of the porous elastic microspheres prepared in the step 2, and stirring the sample for 6 hours in the dark at the stirring speed of 300 rpm.
4. Putting the sample into a vacuum oven, removing bubbles, pouring a small amount of sample into a mold, and curing by using a crawler-type photocuring machine to prepare a tensile sample strip and a dynamic thermal analysis test sample strip; and taking a small amount of samples to coat on an aluminum plate, and curing by using a crawler-type photocuring machine to obtain the photocuring coating.
5. The material is respectively subjected to coating performance, mechanical property, infrared-rheological combined test and laser confocal method volume shrinkage rate test.
Example 5: 0.4g of porous elastic microspheres were added
1. Preparing modified silicon dioxide nano particles:
the preparation method is the same as the above example 2
2. Preparing porous elastic microspheres:
the preparation method is the same as the above example 2
3. Weighing 10g of EA (bisphenol A type epoxy acrylate) and 10g of TPGDA (tripropylene glycol diacrylate) according to the mass ratio of 1:1, uniformly mixing, adding 0.1g of photoinitiator 1173 (2-hydroxy-2-methyl-1-phenyl-1-acetone), adding 0.4g of the porous elastic microspheres prepared in the step 2, and stirring the sample for 6 hours in the dark at the stirring speed of 300 rpm.
4. Putting the sample into a vacuum oven, removing bubbles, pouring a small amount of sample into a mold, and curing by using a crawler-type photocuring machine to prepare a tensile sample strip and a dynamic thermal analysis test sample strip; and taking a small amount of samples to coat on an aluminum plate, and curing by using a crawler-type photocuring machine to obtain the photocuring coating.
5. And respectively carrying out coating performance, mechanical property and infrared-rheological combined test on the material.
Example 6: 0.5g of porous elastic microspheres were added
1. Preparing modified silicon dioxide nano particles:
the preparation method is the same as the above example 2
2. Preparing porous elastic microspheres:
the preparation method is the same as the above example 2
3. Weighing 10g of EA (bisphenol A type epoxy acrylate) and 10g of TPGDA (tripropylene glycol diacrylate) according to the mass ratio of 1:1, uniformly mixing, adding 0.1g of photoinitiator 1173 (2-hydroxy-2-methyl-1-phenyl-1-acetone), adding 0.5g of the porous elastic microspheres prepared in the step 2, and stirring the sample for 6 hours in the dark at the stirring speed of 300 rpm.
4. Putting the sample into a vacuum oven, removing bubbles, pouring a small amount of sample into a mold, and curing by using a crawler-type photocuring machine to prepare a tensile sample strip and a dynamic thermal analysis test sample strip; and taking a small amount of samples to coat on an aluminum plate, and curing by using a crawler-type photocuring machine to obtain the photocuring coating.
5. And respectively carrying out coating performance, mechanical property and infrared-rheological combined test on the material.
In the above examples 1-6, the components of the photo-curing system and the comparison of the content of the components are summarized in the following table 1:
TABLE 1 photocuring System Components and their masses (unit: g)
| Components | Example 1 | Example 2 | Example 3 | Example 4 | Example 5 | Example 6 |
| Matrix resin | EA-10 | EA-10 | EA-10 | EA-10 | EA-10 | EA-10 |
| Reactive diluent | TPGDA-10 | TPGDA-10 | TPGDA-10 | TPGDA-10 | TPGDA-10 | TPGDA-10 |
| 1173 | 0.1 | 0.1 | 0.1 | 0.1 | 0.1 | 0.1 |
| |
0 | 0.1 | 0.2 | 0.3 | 0.4 | 0.5 |
Example results comparative analysis:
1. dynamic thermomechanical analysis test results:
the results of the dynamic thermomechanical analysis testing of examples 1-6 are shown in table 2, indicating that the glass transition temperature Tg of the coatings does not change much.
Table 2 dynamic thermomechanical analysis test results
| Components | Tg/℃ |
| Example 1 | 114 |
| Example 2 | 117 |
| Example 3 | 116 |
| Example 4 | 115 |
| Example 5 | 114 |
| Example 6 | 115 |
Note TgThe glass transition temperature.
2. Results of infrared-rheological coupling test:
the results of the IR-rheological measurements of examples 1-6 are shown in Table 3, which illustrate that the addition of the elastic hollow/porous microspheres delays the onset of the gel point and that the conversion of the double bonds is not affected by the addition of the microspheres. By measuring the stress (Fn) in the Z-axis direction, it was found that the stress was reduced by 46.8%.
TABLE 3 Infrared-rheological combination test results
Note tgelThe gel point time, namely the intersection point of the storage modulus (G ') and the loss modulus (G'), represents the time point when the material starts to form a cross-linked structure and reflects the speed of the curing rate; g'finalThe average value of the material storage modulus (G') within 50s before the end of the infrared-rheological coupling test reflects the rigidity of the material; DBCfinalThe average value of the double bond conversion rate of the material within 50s before the end of the infrared-rheological coupling test is obtained; fnfinalThe average value of the shrinkage stress in the 50s before the end of the test is shown, the negative sign of which represents the direction, and the material shrinks downwards, and the larger the value, the more obvious the volume shrinkage is shown.
Fig. 3 shows a graph of shrinkage stress versus time, illustrating that the final normal stress of examples 2-6 is much lower than that of example 1, and example 4 is reduced by 46.8% compared to that of example 1, illustrating that the addition of microspheres is effective in reducing the shrinkage stress of the photocurable coating, the accumulation of shrinkage stress results in the volume shrinkage of the coating, and illustrating that examples 2-6 are effective in reducing the volume shrinkage of the photocurable coating.
3. Tensile test results:
the tensile test results of examples 1-6 are shown in Table 4, where the Young's modulus of example 6 is similar to that of example 1, and as the content of microspheres increases, the amount of silica attached to the surface increases, improving the mechanical properties of the coating. Examples 2-4 demonstrate that the addition of the microspheres at 0.5% -2.5% can serve to toughen the fiber.
Table 4 tensile test results
4. The volume shrinkage rate test result of the laser confocal method is as follows:
the results of the measurement of the volumetric shrinkage rate of the laser confocal method of examples 1 to 6 are shown in table 5, and the line scanning laser confocal method can accurately record the change of the volume of the material by using the principle of light reflection, which illustrates that the volumetric shrinkage rate of the coating can be efficiently reduced by adding 0.3g of the elastic hollow/porous elastic microspheres, and when 0.3g of the elastic hollow/porous elastic microspheres are added, that is, the adding amount of the elastic hollow/porous elastic microspheres is 1.5% of the total mass of the matrix resin and the monomer, the volumetric shrinkage rate is the smallest, and the volumetric shrinkage rate is reduced by 61.1% as compared with example 4 in example 1.
TABLE 5 volumetric shrinkage test results by confocal laser method
FIG. 4 is a graph showing the change of the cross-section of the sample for the measurement of volume shrinkage by the confocal laser method in example 1, wherein the solid line is the profile curve of the cross-section of the sample before curing, and the dotted line is the profile curve of the cross-section after curing. FIG. 5 is a cross-sectional view of a sample for volume shrinkage measurement according to the confocal laser scanning method of example 4, wherein the solid line shows the appearance of the cross-section of the sample before curing, and the dotted line shows the appearance of the cross-section after curing. The area between the solid line and the dashed line is the area of the cross-section contraction, and the contraction area of fig. 4 is much larger than that of the cross-section of fig. 5.
5. Results of basic performance test of the coating:
the results of the basic property tests of the coatings of examples 1-6 are shown in Table 4, which illustrate that the addition of microspheres does not affect the pencil hardness of the coating, with the pencil hardness of the coatings of examples 1-6 being H, the thickness of the coating increasing with decreasing coating volume shrinkage, and the gloss of the coating decreasing with increasing microsphere content.
TABLE 4 coating basic Performance test results
| Components | Thickness/mum | Glossiness (60 degree) | Hardness of pencil | Hardness/s of pendulum bar |
| Example 1 | 63.6 | 277.3 | H | 174 |
| Example 2 | 75.7 | 255.4 | H | 169 |
| Example 3 | 82.1 | 235.6 | H | 160 |
| Example 4 | 79.2 | 248.4 | H | 145 |
| Example 5 | 75.8 | 220.7 | H | 136 |
| Example 6 | 77.2 | 171.9 | H | 118 |
The above description is only of the preferred embodiments of the present invention, and it should be noted that: it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the invention and these are intended to be within the scope of the invention.
Claims (10)
1. Use of elastic hollow/porous microspheres in a coating characterized by: elastic hollow/porous microspheres are added into the coating to prepare the coating containing the elastic hollow/porous microspheres, and the curing volume shrinkage of the coating with the same formula is reduced by 65 percent before and after the elastic hollow/porous microspheres are added.
2. Use of the elastic hollow/porous microspheres according to claim 1 in coatings characterized by: the volume shrinkage is measured by using the principle of linear confocal measurement: coupling a 3D line scanning laser confocal instrument with an ultraviolet point light source Omicure S2000, dripping a sample on a polypropylene plastic plate, scanning in real time, and finally obtaining the change of the sample volume, wherein the calculation method of the volume shrinkage rate delta V comprises the following steps:
wherein, VENDVolume after curing, VSTARTIs the volume before curing.
3. Use of the elastic hollow/porous microspheres according to claim 1 in coatings characterized by: in the coating, the elastic porous microspheres account for 0.5-2.5 wt% of the total mass of the matrix resin and the active diluent.
4. Use of the elastic hollow/porous microspheres according to claim 3 in coatings characterized by: after matrix resin and monomers are uniformly mixed, adding a photoinitiator and elastic hollow/porous elastic microspheres, and stirring a sample for 4-8h at the stirring speed of 200-350rmp under the condition of keeping out of the sun; and removing air bubbles in the vacuum oven, coating and carrying out photocuring to obtain the photocuring coating.
5. Use of the elastic hollow/porous microspheres according to claim 4 in coatings characterized by: in the coating, the matrix resin is any one or more of epoxy acrylic resin, polyurethane acrylic resin and polyester acrylic resin; the reactive diluent is any one or more of a monofunctional reactive diluent, a difunctional reactive diluent, a trifunctional reactive diluent and a multifunctional reactive diluent; among them, it is preferable that the base resin is bisphenol A type epoxy acrylate and the reactive diluent is tripropylene glycol diacrylate.
6. Use of the elastic hollow/porous microspheres according to claim 1 in coatings characterized by: the elastic hollow/porous microsphere has one or more cavities, and the total volume of the cavities accounts for 40-60% of the volume of the elastic hollow/porous microsphere.
7. Use of the elastic hollow/porous microspheres according to claim 1 in coatings characterized by: the shell layer of the elastic hollow/porous microsphere is a polymer shell layer or a hybrid shell layer of polymer and inorganic particles.
8. Use of the elastic hollow/porous microspheres according to claim 1 in coatings characterized by: the average particle diameter of the elastic hollow/porous microspheres is 1-100 μm, wherein the preferable particle diameter range is 5-50 μm.
9. Use of the resilient hollow/porous microspheres according to any one of claims 1-8 in coatings characterized in that: the elastic hollow/porous microspheres are prepared by a Pickering emulsion method, and comprise the following steps:
(1) preparation of modified SiO2Nano-particles:
firstly, synthesizing the silica nanoparticles by a sol-gel method: mixing deionized water, absolute ethyl alcohol and ammonia water, magnetically stirring at 60 ℃, dropwise adding TEOS, and reacting for 6h to obtain SiO2A dispersion liquid; the SiO2Dropwise adding a silane coupling agent MPS into the dispersion liquid, reacting for 19h at normal temperature, wherein the stirring speed is 300 rmp; after the reaction is finished, SiO is obtained2The MPS dispersion liquid is washed and dried to prepare the modified SiO with double bond modification2A nanoparticle;
(2) preparing elastic hollow/porous microspheres:
respectively preparing a water phase and an oil phase, wherein the oil phase comprises the following components: GBL, GMA, PUA, photoinitiator and modified SiO2Nano particles, wherein the aqueous phase solution is PVA aqueous solution; measuring 1mL of the oil phase, dropwise adding 10mL of the water phase for dispersion and emulsification,preparing the Pickering emulsion, immediately illuminating under an LED lamp, and washing and drying to obtain the elastic hollow/porous hollow microspheres.
10. Use of the resilient hollow/porous microspheres according to claim 9 in coatings characterized in that: the oil phase comprises the following components in parts by weight: 55 parts of GBL, 21 parts of GMA, 21 parts of PUA, 3 parts of photoinitiator 1173 and 5 parts of modified SiO2The nano-particles are dissolved in water phase, and the water phase solution is 1 part of PVA water solution.
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| CN115418154A (en) * | 2022-08-26 | 2022-12-02 | 江南大学 | Self-warning and self-repairing functional coating based on porous microspheres and coating prepared from coating |
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| CN115960483A (en) * | 2023-01-10 | 2023-04-14 | 江南大学 | Method for reducing shrinkage stress of photocureable coating by using pH-responsive cationic microgel |
| CN115975131A (en) * | 2023-02-13 | 2023-04-18 | 江南大学 | Core-shell polymer microsphere and application thereof |
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| CN115418154A (en) * | 2022-08-26 | 2022-12-02 | 江南大学 | Self-warning and self-repairing functional coating based on porous microspheres and coating prepared from coating |
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| CN115960483A (en) * | 2023-01-10 | 2023-04-14 | 江南大学 | Method for reducing shrinkage stress of photocureable coating by using pH-responsive cationic microgel |
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