Photocuring 3D printing silicone rubber ink as well as preparation method and printing method thereof

Abstract

The invention provides photocuring 3D printing silicone rubber ink and a preparation method and a printing method thereof. The photocuring 3D printing silicone rubber ink comprises the following components in parts by mass: 100 parts of vinyl polysiloxane; 4 to 29 parts of sulfydryl grafted polysiloxane; 10 to 50 parts of surface modified fumed silica; 0.1 to 0.5 part of a photoinitiator; 1-5 parts of a light absorber; and 10-220 parts of a diluent. According to the photocuring 3D printing silicone rubber ink, firstly, sulfydryl grafted polysiloxane serves as a cross-linking agent and is cross-linked with vinyl terminated polysiloxane to form a silicone rubber elastomer, secondly, the mechanical property of the silicone rubber elastomer is enhanced through surface modified fumed silica, and then the viscosity of the silicone rubber elastomer is adjusted through the diluent; and finally, the curing depth of the silicone rubber elastomer is adjusted through the light absorber, so that the ink suitable for photocuring 3D printing is obtained, and the contradiction that high mechanical property and low viscosity of traditional photocuring 3D printing silicone rubber cannot be achieved at the same time is overcome.

Description

Technical Field

[0001] The invention relates to a photocurable 3D printing silicone rubber ink and a preparation method and a printing method thereof. Background Art

[0002] Silicone rubber, as a unique polymer elastic material, has a main chain composed of Si-O bonds and attached with organic side groups such as methyl and phenyl. This structure gives silicone rubber the dual properties of inorganic and organic, as well as the characteristics of high and low temperature resistance, aging resistance, excellent electrical insulation and biological stability. At the same time, silicone rubber also has good flexibility and processability, so it has been widely used in many fields, such as light industry, aerospace, transportation, chemical industry, medical and health care, and electronic appliances.

[0003] In recent years, the rapid development of additive manufacturing 3D printing technology has brought revolutionary changes to material processing. It abandons the traditional cutting and assembly mode and can directly generate parts of various shapes from computer graphics data. In the 3D printing of silicone rubber, a printing method based on ink direct writing (DIW) has been developed. For example, in 2014, Duoss et al. of Livermore Laboratory in the United States used Dow Coring's SE1700 silicone rubber as printing slurry for the first time and successfully prepared silicone rubber materials with stacking structures on a direct writing 3D printing platform. The material exhibits similar properties to traditional rubber foam materials.

[0004] However, DIW technology also has some limitations. First, its printing time is long, and it is prone to defects such as collapse during printing and post-curing. Secondly, the nozzle size is large (hundreds of microns), resulting in relatively low printing resolution. In addition, the printing of overhanging structures has high requirements for support materials, which greatly limits the complexity of structural design. Therefore, in the further development of silicone rubber 3D printing technology, improvements and optimizations need to be made to these issues.

[0005] At present, the photosensitive resin is selectively cured by UV light controlled by digital signals, and 3D devices are formed by stacking layer by layer. It has the advantages of fast speed, low energy consumption, high precision, and can prepare complex structure devices. However, since this technology requires raw materials with very low viscosity, it is currently mainly used for printing low viscosity resins (such as acrylic resin). The cured product has a dense, hard and brittle network, but poor elasticity, and is not suitable for application fields such as soft surfaces, biopolymer materials and elastomeric materials.

[0006] In order to apply silicone rubber to photocurable 3D printing, researchers have tried many methods. The researchers used acrylate-modified siloxane as the printing material and used the free radical polymerization reaction of olefins under UV for photocurable 3D printing, but the material is still plastic in nature and does not have the performance of silicone rubber elastomer. The Chinese patent with the publication number CN112300308A, entitled A 3D printing material of a super-strong silicon-based composite elastomer and its preparation method, application and printing method, contains small molecule siloxane, acrylate photopolymerization monomer, surfactant, photoinitiator, alkali generator and water. After 3D printing, the final product is obtained by heating and aging, but this method requires a long aging time and does not characterize the mechanical properties of the material.

[0007] In summary, the elasticity of silicone rubber printed by acrylate-modified light-curing is affected and it does not have the properties of an elastomer. Therefore, there is a need for a silicone rubber that can retain its elasticity.

[0008] Therefore, the researchers selected polymercaptopropylsiloxane and terminal vinyl polysiloxane as the matrix, utilized the mercapto-ene click reaction to cure under UV, and successfully printed polydimethylsiloxane elastomer in an SLA printer. However, its mechanical strength was very low, only 0.13 MPa, which affected its application in more fields.

[0009] The publication number is CN108641369A, and the name is "A photocurable silicone rubber for 3D printing, its preparation method and application", which uses terminal vinyl polysiloxane and polythiol small molecules as prepolymers and surface-modified SiO2 microspheres as reinforcing agents, but the mechanical strength of the printed material is only 0.21MPa.

[0010] In summary, silicone rubber printed by mercapto-ene click reaction photocuring can retain its elasticity, but has the disadvantage of low mechanical strength, which limits its practical application.

[0011] At present, although the silica filler in silicone rubber production can enhance the mechanical properties, it will cause the viscosity of silicone rubber to increase rapidly and is not suitable for photocuring 3D printing. Summary of the invention

[0012] The present invention aims to solve the contradiction between high mechanical properties and low viscosity of conventional photocurable 3D printing silicone rubber, and provides a photocurable 3D printing silicone rubber ink and a preparation method and a printing method thereof.

[0013] The technical method of the present invention is as follows:

[0014] A photocurable 3D printing silicone rubber ink, comprising the following components in parts by weight:

[0015] 100 parts of vinyl polysiloxane;

[0016] 4-29 parts of mercapto-grafted polysiloxane;

[0017] Surface modified fumed silica 10-50 parts;

[0018] Photoinitiator 0.1-0.5 parts;

[0019] 1-5 parts of light absorber;

[0020] Diluent 10-220 parts.

[0021] Specifically, the vinyl polysiloxane is a vinyl-terminated polydimethylsiloxane (also known as vinyl-terminated polydimethylsiloxane), wherein the molecular weight is 9400-28000, the viscosity is 200-1000 cst, and the vinyl content is 0.12%-0.6%. Preferably, the molecular weight is 28000, the viscosity is 1000 cst, and the vinyl content is 0.12%-0.18%.

[0022] Specifically, the mercapto grafted polysiloxane includes at least one of a (mercaptopropyl) methylsiloxane-dimethylsiloxane copolymer and a (mercaptopropyl) methylsiloxane homopolymer. The molecular weight of the (mercaptopropyl) methylsiloxane-dimethylsiloxane copolymer is 3000-8000, the viscosity is 100-200 cst, and the molar ratio of the (mercaptopropyl) methylsiloxane is 4-17%; the molecular weight of the (mercaptopropyl) methylsiloxane homopolymer is 4000-7000, and the viscosity is 75-150 cst.

[0023] Specifically, the surface-modified fumed silica includes at least one of hexamethyldisilazane-modified fumed silica and polydimethylsiloxane-modified fumed silica. The particle size of the surface-modified fumed silica is 7-40 nm.

[0024] Specifically, the photoinitiator is a free radical photoinitiator; the free radical photoinitiator includes at least one of 2,4,6 (trimethylbenzoyl) diphenyl phosphine oxide and 2,4,6-trimethylbenzoyl ethyl phosphonate.

[0025] Specifically, the light absorber includes at least one of 2-isopropylthioxanthone, Sudan red and derivatives thereof.

[0026] Specifically, the diluent is trimethylbenzene, and the trimethylbenzene includes at least one of 1,3,5-trimethylbenzene, 1,2,3-trimethylbenzene, and 1,2,4-trimethylbenzene.

[0027] The present invention also provides a method for preparing photocurable 3D printing silicone rubber ink, the preparation method comprising: mixing vinyl polysiloxane, mercapto grafted polysiloxane and a photoinitiator evenly; then adding surface modified fumed silica and mixing evenly; then adding a light absorber and a diluent and mixing evenly to obtain photocurable 3D printing silicone rubber ink.

[0028] The present invention also provides a light-curing 3D printing method of light-curing 3D printing silicone rubber ink, the light-curing 3D printing method comprising: obtaining a slice image of a 3D data model; pouring the light-curing 3D printing silicone rubber ink into a material tank of a DLP type light-curing 3D printer, and 3D printing the slice image of the 3D data model; wherein the wavelength of the printing light source is 300-450nm, and the light power is 10-30mW / cm 2 , printing layer thickness 5-150μm.

[0029] The beneficial effects of the present invention are:

[0030] 1. The photocurable 3D printing silicone rubber ink of the present invention first uses mercapto-grafted polysiloxane as a crosslinking agent to crosslink with vinyl-terminated polysiloxane to form a silicone rubber elastomer, then enhances the mechanical properties of the silicone rubber elastomer by surface-modified fumed silica, then adjusts the viscosity of the silicone rubber elastomer by a diluent, and finally adjusts the curing depth of the silicone rubber elastomer by a light absorber to obtain an ink suitable for photocurable 3D printing, thereby overcoming the contradiction that high mechanical properties and low viscosity of traditional photocurable 3D printing silicone rubber cannot be achieved at the same time.

[0031] Second, the diluent of the present invention has high boiling point and flash point, low saturated vapor pressure, low volatility and toxicity, and has good applicability and safety in 3D printing.

[0032] 3. The raw materials of the light-curable 3D printing silicone rubber ink of the present invention are easy to obtain, and the preparation method thereof is simple and convenient.

[0033] 4. The light-curing 3D printing method of the present invention has good printing accuracy, high fidelity of the finished product, good elasticity, high tensile strength, and has good application prospects.

[0034] 5. The surface modified fumed silica of the present invention has good compatibility with the silicone rubber matrix, and has good printing effect and mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The DLP printing sample photo of Example 1;

[0036] Figure 2 This is a DLP printing sample photo of Example 2;

[0037] Figure 3This is a DLP printing sample photo of Example 3;

[0038] Figure 4 This is a DLP printing sample photo of Example 4;

[0039] Figure 5 This is a DLP printing sample photo of Example 5;

[0040] Figure 6 This is a DLP printing sample photo of Example 6;

[0041] Figure 7 This is a DLP printing sample photo of Example 8;

[0042] Figure 8 This is a DLP printing sample photo of Example 9;

[0043] Fig. 9 These are the tensile properties diagrams of the DLP printed samples of Examples 1-9. DETAILED DESCRIPTION

[0044] The technical solution of the present invention is described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] The invention provides a photocurable 3D printing silicone rubber ink, comprising the following components in parts by mass: 100 parts of vinyl polysiloxane; 4-29 parts of mercapto-grafted polysiloxane; 10-50 parts of surface-modified fumed silica; 0.1-0.5 parts of a photoinitiator; 1-5 parts of a light absorber; and 10-220 parts of a diluent.

[0046] For example, the mercapto-grafted polysiloxane may be 5 parts, 7 parts, 12 parts, 15 parts, 17 parts, 20 parts. The surface-modified fumed silica may be 12 parts, 15 parts, 17 parts, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts. The photoinitiator may be 0.2 parts, 0.3 parts, 0.4 parts. The light absorber may be 2 parts, 3 parts, 4 parts. The diluent may be 15 parts, 30 parts, 50 parts, 70 parts, 90 parts, 110 parts, 130 parts, 150 parts, 170 parts, 190 parts, 210 parts.

[0047] The present invention uses vinyl-terminated polysiloxane and mercapto-grafted polysiloxane as a matrix, surface-modified fumed silica as a reinforcing agent, trimethylbenzene as a diluent, and a photoinitiator and a light absorber as auxiliary agents to prepare silicone rubber ink suitable for photocurable 3D printing, and then prints silicone rubber elastomers of different patterns and shapes on a photocurable 3D printer.

[0048] Here, surface-modified fumed silica increases viscosity, but at the same time enhances the mechanical properties of silicone rubber elastomers. Therefore, diluents are subsequently added to reduce viscosity, thereby overcoming the contradiction between high mechanical properties and low viscosity of traditional photocurable 3D printed silicone rubber.

[0049] Specifically, the vinyl polysiloxane is a vinyl-terminated polydimethylsiloxane (also known as vinyl-terminated polydimethylsiloxane), wherein the molecular weight is 9400-28000, the viscosity is 200-1000 cst, and the vinyl content is 0.12%-0.6%. Preferably, the molecular weight is 28000, the viscosity is 1000 cst, and the vinyl content is 0.12%-0.18%.

[0050] Specifically, the mercapto grafted polysiloxane includes at least one of a (mercaptopropyl) methylsiloxane-dimethylsiloxane copolymer and a (mercaptopropyl) methylsiloxane homopolymer. The molecular weight of the (mercaptopropyl) methylsiloxane-dimethylsiloxane copolymer is 3000-8000, the viscosity is 100-200 cst, and the molar ratio of the (mercaptopropyl) methylsiloxane is 4-17%. Preferably, the molar ratio of the (mercaptopropyl) methylsiloxane is 13-17%. The molecular weight of the (mercaptopropyl) methylsiloxane homopolymer is 4000-7000, and the viscosity is 75-150 cst.

[0051] Here, the molecular weight, viscosity and content of vinyl polysiloxane and mercapto grafted polysiloxane mainly affect the crosslinking degree of the cured product, and thus affect the mechanical properties. For example, a cured product with a low crosslinking degree is softer, which affects printing and molding; while a high degree of crosslinking will make the cured product hard and brittle, and reduce elasticity and mechanical strength. The present invention optimizes the molecular weight, viscosity and content of vinyl polysiloxane and mercapto grafted polysiloxane, so as to achieve the best elasticity and mechanical strength performance.

[0052] Specifically, the surface-modified fumed silica includes at least one of hexamethyldisilazane-modified fumed silica and polydimethylsiloxane-modified fumed silica. The particle size of the surface-modified fumed silica is 7-40 nm. For example, the particle size may be 10 nm, 15 nm, 20 nm, 25 nm, or 35 nm.

[0053] Specifically, the photoinitiator is a free radical photoinitiator; the free radical photoinitiator includes at least one of 2,4,6-trimethylbenzoyl diphenylphosphine oxide (TPO) and 2,4,6-trimethylbenzoyl ethylphosphonate (TPO-L).

[0054] Specifically, the light absorber includes at least one of 2-isopropylthioxanthone (ITX), Sudan red and its derivatives (for example, Sudan red G may be used).

[0055] Specifically, the diluent is trimethylbenzene, and trimethylbenzene includes at least one of 1,3,5-trimethylbenzene (mesitylene), 1,2,3-trimethylbenzene, and 1,2,4-trimethylbenzene. Trimethylbenzene has high boiling point and flash point, low saturated vapor pressure, low volatility and toxicity, and has good applicability and safety in 3D printing.

[0056] The present invention also provides a method for preparing a photocurable 3D printing silicone rubber ink, the preparation method comprising: uniformly mixing vinyl polysiloxane, mercapto-grafted polysiloxane and a photoinitiator; then adding surface-modified fumed silica and mixing them uniformly; then adding a light absorber and a diluent and mixing them uniformly to obtain a photocurable 3D printing silicone rubber ink. Here, a planetary mixer is used for mixing. The mixing time is 1-10 minutes. During mixing, the rotation speed of the planetary mixer is 1000-2000rpm.

[0057] The present invention also provides a method for photocuring 3D printing of photocurable 3D printing silicone rubber ink, the method comprising: obtaining a slice image of a 3D data model; pouring the photocurable 3D printing silicone rubber ink into a material tank of a DLP type photocurable 3D printer, and performing 3D printing on the slice image of the 3D data model. The wavelength of the printing light source is 300-450nm, and the light power is 10-30mW / cm 2 , the printing layer thickness is 5-150μm. Here, the printing light source wavelength can be 330nm, 405nm, 430nm. The light power can be 15mW / cm 2 , 20mW / cm 2 、25mW / cm 2 The printing layer thickness can be 10μm, 50μm, 100μm.

[0058] In one embodiment, the exposure time of the bottom layer is set to 20-40 seconds, the exposure time of each layer is set to 5-7 seconds, and the standing time is set to 3-5 seconds.

[0059] In one embodiment, the sample is removed after printing, soaked in a dichloromethane solution for 1-5 minutes to remove the residual uncured ink on the surface and replace the high-boiling-point trimethylbenzene diluent, and then placed at room temperature for volatilization or vacuum drying (for example, 40°C) to obtain the final printed sample. Here, the photocuring 3D printing method of the present invention removes the solvent by solvent displacement volatilization after printing to obtain a finished product with higher mechanical properties and printing accuracy. At the same time, the shrinkage during the solvent volatilization process occurs in an isotropic, repeatable and predictable manner, and the unidirectional shrinkage rate is obtained by comparing the width or thickness of the dry sample with the size of the printed model. The 3D printing accuracy is the plane accuracy of the printed groove sample. In one embodiment, the printed product has a tensile strength of 0.7-3.0MPa, a fracture growth rate of 132.1%-713.3%, a printing accuracy of 158-200μm, and a unidirectional shrinkage rate of -0.4%--24.7%.

[0060] The present invention will be further described in detail below with reference to specific embodiments.

[0061] Example 1

[0062] Preparation of photocurable 3D printing silicone rubber ink: 20 g of vinyl-terminated polydimethylsiloxane (molecular weight 28000, viscosity 1000 cst, vinyl content 0.12-0.18%), 4.408 g of (mercaptopropyl) methylsiloxane-dimethylsiloxane copolymer (molecular weight 3000-4000, viscosity 100-200 cst, (mercaptopropyl) methylsiloxane molar ratio of 13-17%) and 75 mg of photoinitiator TPO-L were weighed into a container, mixed with a planetary mixer (2000 rpm, 3 min), and then 2.44 g of hexamethyldisilazane-modified fumed silica was added, and then mixed evenly with a planetary mixer. 2.44 mL of 2-isopropylthioxanthone (ITX) in mesitylene solution (1.72 mg / mL) was added to the obtained slurry as a light absorber to adjust the curing depth, and the obtained mixture was mixed evenly by a planetary mixer to obtain a light-cured 3D printing silicone rubber ink. The viscosity was tested by a rotational viscometer and was 1062.7 cP.

[0063] DLP printing: Pour the above printing ink into the material tank of the DLP type light-curing 3D printer, set the bottom exposure time to 40s, the layer thickness to 50μm, the exposure time for each layer to 6s, and the standing time to 4s, and print the pre-sliced ​​3D model. After printing, remove the sample and soak it in a dichloromethane solution for 2min to remove the residual uncured ink on the surface, and then leave it at room temperature to evaporate to obtain the final printed sample. The tensile strength of the printed sample is 0.7MPa, the fracture growth rate is 303.5%, the printing accuracy is 200μm, and the unidirectional shrinkage rate is -0.4%.

[0064] Example 2

[0065] Preparation of photocurable 3D printing silicone rubber ink: 30 g of vinyl-terminated polydimethylsiloxane (molecular weight 28000, viscosity 1000 cst, vinyl content 0.12-0.18%), 6.612 g of (mercaptopropyl) methylsiloxane-dimethylsiloxane copolymer (molecular weight 3000-4000, viscosity 100-200 cst, (mercaptopropyl) methylsiloxane molar ratio of 13-17%) and 112.5 mg of photoinitiator TPO-L were weighed into a container, mixed with a planetary mixer (2000 rpm, 3 min), and then 7.32 g of hexamethyldisilazane-modified fumed silica was added, and then mixed evenly with a planetary mixer. 3.65 mL of 2-isopropylthioxanthone (ITX) in mesitylene solution (1.72 mg / mL) was added to the obtained slurry as a light absorber to adjust the curing depth, and 30 mL of mesitylene was added as a diluent, and the obtained mixture was mixed evenly by a planetary mixer to obtain a light-cured 3D printing silicone rubber ink. The viscosity was tested by a rotational viscometer and was 297.3 cP.

[0066] DLP printing: Pour the above printing ink into the material tank of the DLP type light-curing 3D printer, set the bottom exposure time to 40s, the layer thickness to 50μm, the exposure time for each layer to 6s, and the standing time to 4s, and print the pre-sliced ​​3D model. After printing, remove the sample and soak it in a dichloromethane solution for 2min to remove the residual uncured ink on the surface and replace the high-boiling point mesitylene diluent, then leave it to evaporate at room temperature and vacuum dry (40℃, 3h) to obtain the final printed sample. The tensile strength of the printed sample is 1.6MPa, the fracture growth rate is 409.9%, the printing accuracy is 196μm, and the unidirectional shrinkage rate is -14.7%.

[0067] Example 3

[0068] Preparation of photocurable 3D printing silicone rubber ink: 20 g of vinyl-terminated polydimethylsiloxane (molecular weight 28000, viscosity 1000 cst, vinyl content 0.12-0.18%), 4.408 g of (mercaptopropyl) methylsiloxane-dimethylsiloxane copolymer (molecular weight 3000-4000, viscosity 100-200 cst, (mercaptopropyl) methylsiloxane molar ratio of 13-17%) and 75 mg of photoinitiator TPO-L were weighed into a container, mixed with a planetary mixer (2000 rpm, 3 min), and then 7.32 g of hexamethyldisilazane-modified fumed silica was added, and then mixed evenly with a planetary mixer. 2.44 mL of 2-isopropylthioxanthone (ITX) in mesitylene solution (1.72 mg / mL) was added to the obtained slurry as a light absorber to adjust the curing depth, and 30 mL of mesitylene was added as a diluent, and the obtained mixture was mixed evenly by a planetary mixer to obtain a light-cured 3D printing silicone rubber ink. The viscosity was tested by a rotational viscometer and was 443.7 cP.

[0069] DLP printing: Pour the above printing ink into the material tank of the DLP type light-curing 3D printer, set the bottom exposure time to 40s, the layer thickness to 50μm, the exposure time for each layer to 6s, and the standing time to 4s, and print the pre-sliced ​​3D model. After printing, remove the sample and soak it in a dichloromethane solution for 2min to remove the residual uncured ink on the surface and replace the high-boiling point mesitylene diluent, then leave it to evaporate at room temperature and vacuum dry (40℃, 3h) to obtain the final printed sample. The tensile strength of the printed sample is 2.7MPa, the fracture growth rate is 410.0%, the printing accuracy is 187μm, and the unidirectional shrinkage rate is -19.3%.

[0070] Example 4

[0071] 20 g of vinyl-terminated polydimethylsiloxane (molecular weight 28,000, viscosity 1,000 cst, vinyl content 0.12-0.18%), 4.408 g of (mercaptopropyl)methylsiloxane-dimethylsiloxane copolymer (molecular weight 3,000-4,000, viscosity 100-200 cst, (mercaptopropyl)methylsiloxane molar ratio 13-17%) and 75 mg of photoinitiator TPO-L were weighed into a container, mixed with a planetary mixer (2,000 rpm, 3 min), and then 9.76 g of hexamethyldisilazane-modified fumed silica was added, followed by mixing evenly with a planetary mixer. 2.44 mL of 2-isopropylthioxanthone (ITX) in mesitylene solution (1.72 mg / mL) was added to the obtained slurry as a light absorber to adjust the curing depth, and 50 mL of mesitylene was added as a diluent. The obtained mixture was mixed evenly by a planetary mixer to obtain a light-cured 3D printing silicone rubber ink. The viscosity was tested by a rotational viscometer and was 310.3 cP.

[0072] DLP printing: Pour the above printing ink into the material tank of the DLP type light-curing 3D printer, set the bottom exposure time to 40s, the layer thickness to 50μm, the exposure time for each layer to 6s, and the standing time to 4s, and print the pre-sliced ​​3D model. After printing, remove the sample and soak it in a dichloromethane solution for 2min to remove the residual uncured ink on the surface and replace the high-boiling point mesitylene diluent, then leave it to evaporate at room temperature and vacuum dry (40℃, 3h) to obtain the final printed sample. The tensile strength of the printed sample is 2.3MPa, the fracture growth rate is 301.6%, the printing accuracy is 170μm, and the unidirectional shrinkage rate is -24.7%.

[0073] Example 5

[0074] Preparation of photocurable 3D printing silicone rubber ink: 20 g of vinyl-terminated polydimethylsiloxane (molecular weight 28000, viscosity 1000 cst, vinyl content 0.12-0.18%), 4.408 g of (mercaptopropyl) methylsiloxane-dimethylsiloxane copolymer (molecular weight 3000-4000, viscosity 100-200 cst, (mercaptopropyl) methylsiloxane molar ratio of 13-17%) and 75 mg of photoinitiator TPO-L were weighed into a container, mixed with a planetary mixer (2000 rpm, 3 min), and then 7.32 g of hexamethyldisilazane-modified fumed silica was added, and then mixed evenly with a planetary mixer. 2.44 mL of 2-isopropylthioxanthone (ITX) in mesitylene solution (1.72 mg / mL) was added to the obtained slurry as a light absorber to adjust the curing depth, and 35 mL of mesitylene was added as a diluent. The obtained mixture was mixed evenly by a planetary mixer to obtain a light-cured 3D printing silicone rubber ink. The viscosity was tested by a rotational viscometer and was 271.7 cP.

[0075] DLP printing: Pour the above printing ink into the material tank of the DLP type light-curing 3D printer, set the bottom exposure time to 40s, the layer thickness to 50μm, the exposure time for each layer to 6s, and the standing time to 4s, and print the pre-sliced ​​3D model. After printing, remove the sample and soak it in a dichloromethane solution for 2min to remove the residual uncured ink on the surface and replace the high-boiling point mesitylene diluent, then leave it to evaporate at room temperature and vacuum dry (40℃, 3h) to obtain the final printed sample. The tensile strength of the printed sample is 2.2MPa, the fracture growth rate is 416.3%, the printing accuracy is 178μm, and the unidirectional shrinkage rate is -21.7%.

[0076] Example 6

[0077] Preparation of photocurable 3D printing silicone rubber ink: 10 g of vinyl-terminated polydimethylsiloxane (molecular weight 28000, viscosity 1000 cst, vinyl content 0.12-0.18%), 0.955 g of (mercaptopropyl) methylsiloxane-dimethylsiloxane copolymer (molecular weight 3000-4000, viscosity 100-200 cst, (mercaptopropyl) methylsiloxane molar ratio of 13-17%) and 37.5 mg of photoinitiator TPO-L were weighed into a container, mixed with a planetary mixer (2000 rpm, 3 min), and then 3.29 g of hexamethyldisilazane-modified fumed silica was added, and then mixed evenly with a planetary mixer. 1.1 mL of 2-isopropylthioxanthone (ITX) in mesitylene solution (1.72 mg / mL) was added to the obtained slurry as a light absorber to adjust the curing depth, and 17.5 mL of mesitylene was added as a diluent. The obtained mixture was mixed evenly by a planetary mixer to obtain a light-cured 3D printing silicone rubber ink.

[0078] DLP printing: Pour the above printing ink into the material tank of the DLP type light-curing 3D printer, set the bottom exposure time to 40s, the layer thickness to 50μm, the exposure time for each layer to 6s, and the standing time to 4s, and print the pre-sliced ​​3D model. After printing, remove the sample and soak it in a dichloromethane solution for 2min to remove the residual uncured ink on the surface and replace the high-boiling point mesitylene diluent, then leave it to evaporate at room temperature and vacuum dry (40℃, 3h) to obtain the final printed sample. The tensile strength of the printed sample is 2.0MPa, the fracture growth rate is 246.2%, the printing accuracy is 170μm, and the unidirectional shrinkage rate is -22.4%.

[0079] Example 7

[0080] Preparation of photocurable 3D printing silicone rubber ink: 20 g of vinyl-terminated polydimethylsiloxane (molecular weight 28000, viscosity 1000 cst, vinyl content 0.12-0.18%), 5.66 g of (mercaptopropyl) methylsiloxane-dimethylsiloxane copolymer (molecular weight 6000-8000, viscosity 120-170 cst, (mercaptopropyl) methylsiloxane molar ratio of 4-6%) and 75 mg of photoinitiator TPO-L were weighed into a container, mixed with a planetary mixer (2000 rpm, 3 min), and then 7.32 g of hexamethyldisilazane-modified fumed silica was added, and then mixed evenly with a planetary mixer. 2.57 mL of 2-isopropylthioxanthone (ITX) in mesitylene solution (1.72 mg / mL) was added to the obtained slurry as a light absorber to adjust the curing depth, and 35 mL of mesitylene was added as a diluent, and the obtained mixture was mixed evenly by a planetary mixer to obtain a light-cured 3D printing silicone rubber ink. The viscosity was tested by a rotational viscometer and was 518.0 cP.

[0081] DLP printing: Pour the above printing ink into the material tank of the DLP type light-curing 3D printer, set the bottom exposure time to 40s, the layer thickness to 50μm, the exposure time for each layer to 6s, and the standing time to 4s, and print the pre-sliced ​​3D model. After printing, remove the sample and soak it in a dichloromethane solution for 2min to remove the residual uncured ink on the surface and replace the high-boiling-point mesitylene diluent, then leave it to evaporate at room temperature and vacuum dry (40℃, 3h) to obtain the final printed sample. The ink is easy to break during the printing process, and the printed sample is easy to be incomplete, with a unidirectional shrinkage rate of -22.0%.

[0082] Example 8

[0083] Preparation of photocurable 3D printing silicone rubber ink: 20g vinyl-terminated polydimethylsiloxane (molecular weight 28000, viscosity 1000cst, vinyl content 0.12-0.18%), 0.804g (mercaptopropyl) methylsiloxane homopolymer (molecular weight 4000-7000, viscosity 75-150cst) and 75mg photoinitiator TPO-L were weighed into a container, and mixed by a planetary mixer (2000rpm, 3min), and then 6.24g hexamethyldisilazane-modified fumed silica was added, and then mixed evenly by a planetary mixer. 2.08mL 2-isopropylthioxanthone (ITX) in mesitylene solution (1.72mg / mL) was added to the obtained slurry as a light absorber to adjust the curing depth, and 30mL mesitylene was added as a diluent, and the obtained mixture was mixed evenly by a planetary mixer to obtain photocurable 3D printing silicone rubber ink. The viscosity was measured by a rotational viscometer and was 512.3 cP.

[0084] DLP printing: Pour the above printing ink into the material tank of the DLP type light-curing 3D printer, set the bottom exposure time to 40s, the layer thickness to 50μm, the exposure time for each layer to 6s, and the standing time to 4s, and print the pre-sliced ​​3D model. After printing, remove the sample and soak it in a dichloromethane solution for 2min to remove the residual uncured ink on the surface and replace the high-boiling-point mesitylene diluent, and then leave it at room temperature to evaporate to obtain the final printed sample. The tensile strength of the printed sample is 3.0MPa, the fracture growth rate is 713.3%, the printing accuracy is 158μm, and the unidirectional shrinkage rate is -20.5%.

[0085] Example 9

[0086] Preparation of photocurable 3D printing silicone rubber ink: 20 g of vinyl-terminated polydimethylsiloxane (molecular weight 9400, viscosity 200 cst, vinyl content 0.4-0.6%), 4.408 g of (mercaptopropyl) methylsiloxane-dimethylsiloxane copolymer (molecular weight 3000-4000, viscosity 100-200 cst, (mercaptopropyl) methylsiloxane molar ratio of 13-17%) and 75 mg of photoinitiator TPO-L were weighed into a container, mixed with a planetary mixer (2000 rpm, 3 min), and then 7.32 g of hexamethyldisilazane-modified fumed silica was added, and then mixed evenly with a planetary mixer. 2.44 mL of 2-isopropylthioxanthone (ITX) in mesitylene solution (1.72 mg / mL) was added to the obtained slurry as a light absorber to adjust the curing depth, and 35 mL of mesitylene was added as a diluent. The obtained mixture was mixed evenly by a planetary mixer to obtain a light-cured 3D printing silicone rubber ink. The viscosity was tested by a rotational viscometer and was 234.3 cP.

[0087] DLP printing: Pour the above printing ink into the material tank of the DLP type light-curing 3D printer, set the bottom exposure time to 40s, the layer thickness to 50μm, the exposure time for each layer to 6s, and the standing time to 4s, and print the pre-sliced ​​3D model. After printing, remove the sample and soak it in a dichloromethane solution for 2min to remove the residual uncured ink on the surface and replace the high-boiling-point mesitylene diluent, and then leave it at room temperature to evaporate to obtain the final printed sample. The tensile strength of the printed sample is 1.1MPa, the fracture growth rate is 132.1%, the printing accuracy is 170μm, and the unidirectional shrinkage rate is -21.3%.

[0088] Figure 1-8 The printed samples of Examples 1-6 and 8-9 show their printing accuracy.

[0089] Fig. 9 The tensile performance diagram of Examples 1-6 and 8-9 shows their tensile strength.

[0090]

[0091]

[0092] Table 1

[0093] From Table 1 we can see that:

[0094] The tensile strength of Examples 1-9 of the present invention is significantly higher than that of the prior art, and is in the range of 0.7-3.0 MPa.

[0095] The fracture growth rates of Examples 1-9 of the present invention are much higher than those of the prior art, and range from 132.1% to 713.3%.

[0096] The DLP of Examples 1-9 of the present invention has a relatively high printing accuracy, and the range is 158-200 μm.

[0097] It can be seen from Examples 1-9 of the present invention that increasing the content of fumed silica has an effect on improving the tensile strength.

Claims

1. A photocurable 3D printing silicone rubber ink, characterized in that: The composition includes the following components in parts by weight: 100 parts of vinyl polysiloxane; 4-29 parts of mercapto-grafted polysiloxane; Surface modified fumed silica 10-50 parts; Photoinitiator 0.1-0.5 parts; 1-5 parts of light absorber; Diluent 10-220 parts.

2. The light-curable 3D printing silicone rubber ink according to claim 1, characterized in that: The vinyl polysiloxane is a vinyl-terminated polydimethylsiloxane, wherein the molecular weight is 9400-28000, the viscosity is 200-1000 cst, and the vinyl content is 0.12%-0.6%; Preferably, the molecular weight is 28000, the viscosity is 1000 cst, and the vinyl content is 0.12%-0.18%.

3. The light-curable 3D printing silicone rubber ink according to claim 1, characterized in that: The mercapto-grafted polysiloxane includes at least one of a (mercaptopropyl) methylsiloxane-dimethylsiloxane copolymer and a (mercaptopropyl) methylsiloxane homopolymer; Wherein, the molecular weight of the (mercaptopropyl) methylsiloxane-dimethylsiloxane copolymer is 3000-8000, the viscosity is 100-200 cst, and the molar ratio of (mercaptopropyl) methylsiloxane is 4-17%; Among them, the molecular weight of (mercaptopropyl)methylsiloxane homopolymer is 4000-7000 and the viscosity is 75-150cst.

4. The light-curable 3D printing silicone rubber ink according to claim 1, characterized in that: The surface modified fumed silica includes at least one of hexamethyldisilazane modified fumed silica and polydimethylsiloxane modified fumed silica.

5. The light-curable 3D printing silicone rubber ink according to claim 1, characterized in that: The particle size of the surface modified fumed silica is 7-40 nm.

6. The light-curable 3D printing silicone rubber ink according to claim 1, characterized in that: The photoinitiator is a free radical photoinitiator; The free radical photoinitiator includes at least one of 2,4,6-trimethylbenzoyldiphenylphosphine oxide and ethyl 2,4,6-trimethylbenzoylphosphonate.

7. The light-curable 3D printing silicone rubber ink according to claim 1, characterized in that: The light absorber includes at least one of 2-isopropylthioxanthone, Sudan red and derivatives thereof.

8. The light-curable 3D printing silicone rubber ink according to claim 1, characterized in that: The diluent is trimethylbenzene, and the trimethylbenzene includes at least one of 1,3,5-trimethylbenzene, 1,2,3-trimethylbenzene, and 1,2,4-trimethylbenzene.

9. A method for preparing a photocurable 3D printing silicone rubber ink, characterized in that: The preparation method comprises: The vinyl polysiloxane, the mercapto-grafted polysiloxane and the photoinitiator are mixed uniformly; Then add surface modified fumed silica and mix evenly; Then add a light absorber and a diluent and mix them evenly to obtain a light-curing 3D printing silicone rubber ink.

10. A method for photocuring 3D printing of photocurable 3D printing silicone rubber ink, characterized in that: The light-curing 3D printing method comprises: Acquire slice images of the 3D data model; Pour the light-curing 3D printing silicone rubber ink into the material tank of the DLP light-curing 3D printer, and perform 3D printing on the sliced ​​image of the 3D data model; The wavelength of the printing light source is 300-450nm, and the light power is 10-30mW / cm 2 , printing layer thickness 5-150μm.

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