Silicone rubber foam material and its preparation method and application

Abstract

This invention belongs to the field of silicone rubber foam materials and 3D printing technology, specifically relating to a silicone rubber foam material, its preparation method, and its applications. This invention utilizes photopolymerization to prepare a silicone rubber foam material using a chemical foaming method. By cleverly controlling the content and amount of reactive functional groups such as mercapto, vinyl, silanol, and hydroxyl groups, controllable foaming is achieved during the photopolymerization process. This control can significantly shorten the preparation time of the silicone rubber foam material and controllably adjust the pore size, resulting in a silicone rubber foam material with small and dense pores. Compared with existing physical foaming methods, it has the advantages of simple and rapid preparation. This invention further extends the photopolymerization process to 3D technology, enriching the processing methods of silicone rubber foam, enabling customized manufacturing and macroscopic structural design, and further expanding its application areas.

Description

Technical Field

[0001] This invention belongs to the field of silicone rubber foam materials and their 3D printing technology. More specifically, it relates to a silicone rubber foam material, its preparation method, and its applications. Background Technology

[0002] Silicone rubber foam is a porous polymer elastic material prepared by foaming silicone rubber. It has high thermal stability, good insulation, heat insulation and moisture resistance, and excellent shock resistance. It is an ideal lightweight encapsulation material that can be used in various electronic components, instruments, meters, aircraft wheel, insulation interlayer filling material, flotation material in salt spray atmosphere, sealing material, and filling, repair and lining material in orthopedic surgery.

[0003] There are two types of foaming technology for silicone rubber foam: solution-based pore formation and gas foaming. Solution-based pore formation involves mixing water-soluble inorganic salts into the silicone rubber compound, followed by heating and vulcanization. The inorganic salts are then dissolved through a water washing process to produce a open-cell silicone rubber foam material. The advantage of this technology is that the pore size, density, and other parameters of the silicone rubber foam material can be controlled by adjusting the type and amount of water-soluble inorganic salts. The disadvantages are that the water washing process generates a large amount of wastewater, causing severe pollution, and it cannot produce closed-cell foam materials. Gas foaming technology can be divided into physical foaming and chemical foaming. Physical foaming achieves foaming through the expansion of inert gases, the vaporization of low-boiling-point liquids, or the filling and dissolution of particles. Chemical foaming involves blending polymers with chemical foaming agents or generating gas through the reaction between two chemical groups. Chemical foaming agents are most commonly used in industries such as extrusion foaming because their application requires only minor modifications to existing equipment. Compared to using chemical foaming agents, physical foaming can induce a more uniform foam structure, but it requires sophisticated equipment and has a more complex preparation process. Compared to physical foaming, chemical foaming has the advantages of simpler and more efficient processes, but the process is difficult to control. For example, Chinese patent application CN114752219A discloses a room-temperature foamed silicone rubber material. This silicone rubber foam material belongs to thermosetting foamed silicone rubber materials. The foaming and curing processes in the preparation process are carried out in steps. The curing process is achieved by adding hydrogen-containing silicone oil in the second step. This results in a larger pore size in the obtained material (the appearance of the foam is shown in the camera image, where obvious pores can be observed. If the pore size is less than 100μm, it is difficult to observe with the naked eye), and the foaming time is relatively long (1-10 hours).

[0004] Therefore, there is an urgent need to develop a silicone rubber foam material with uniform cell size, a large number of cells, and a short foaming time. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the defects and shortcomings of existing chemical foaming methods, which produce silicone rubber foam with large pore sizes (greater than 100 μm) and difficult-to-control foaming rate, resulting in silicone rubber foam materials with uniform pores, a large number of pores, and small pore sizes (less than 100 μm). The present invention provides a silicone rubber foam material with uniform pores, a large number of pores, and a short foaming time.

[0006] Another object of the present invention is to provide a method for preparing the silicone rubber foam material.

[0007] Another object of the present invention is to provide the application of the said silicone rubber foam material.

[0008] The above-mentioned objective of this invention is achieved through the following technical solution:

[0009] This invention protects a silicone rubber foam material, comprising the following components by total mass percentage:

[0010] 40%–50% side mercapto silicone oil;

[0011] 45%–55% end vinyl hydrogen-containing silicone oil;

[0012] 1%–5% hydroxyl compounds;

[0013] 1%–2% photoinitiator;

[0014] 0.5%–2% platinum catalyst;

[0015] The side-thiol silicone oil has a thiol content of 0.5–2 mmol / g;

[0016] The vinyl content of the terminal vinyl hydrogen-containing silicone oil is 0.3-0.8 mmol / g, and the hydrogen content is 8-11 mmol / g;

[0017] The hydroxyl-containing compound is one or more of alcohols and hydroxyl silicone oils;

[0018] The hydroxyl content of the hydroxyl silicone oil is 0.6–1 mmol / g;

[0019] The alcohols mentioned are alcohols with a boiling point >90℃.

[0020] This invention addresses the technical problem that existing chemical foaming methods primarily produce macroporous silicone rubber foams with pore sizes greater than 100 μm, and that the foaming rate is difficult to control. By controlling the content and amount of reactive functional groups (thiol, vinyl, silanol, and hydroxyl), this invention differs from traditional platinum-catalyzed hydrosilylation curing of silanol bonds and carbon-carbon double bonds. It utilizes the rapid curing of the thiol-alkene click reaction to limit platinum-catalyzed silanol bond condensation and dehydrogenation foaming with alcohols, thereby restricting pore aggregation and expansion. This results in a silicone rubber material with uniform pores, a large number of pores, and a small pore size (less than 100 μm).

[0021] Furthermore, the side-thiol silicone oil is a polysiloxane containing thiol groups on its side chain, and the terminal-thiol silicone oil is a polysiloxane containing thiol groups on its main chain. If terminal-thiol silicone oil is used, it is difficult to form a cross-linked network with terminal vinyl hydrogen-containing silicone oil. As for the content of thiol groups in the thiol silicone oil, too little will make it difficult for the foam to be cured and formed, and too much will make the curing rate inconsistent with the foaming rate, making it difficult to form small and dense foam.

[0022] Furthermore, the structural formula of the side-thiol silicone oil is:

[0023]

[0024] In the formula, m is selected from any integer from 1 to 400, and n is selected from any integer from 1 to 80.

[0025] Furthermore, the side-thiol silicone oil can be obtained by purchasing from the market or by making it in-house.

[0026] Furthermore, as an optional approach, the preparation method of the side-thiol silicone oil includes the following steps:

[0027] Hexamethyldisiloxane, thiopropylmethyldimethoxysilane, an organosilicon intermediate, an acidic catalyst, and water are mixed and reacted thoroughly at 60–90°C. The resulting product is purified to obtain side-thiol silicone oil. The specific reaction equation is as follows:

[0028]

[0029] Furthermore, the organosilicon intermediate includes linear siloxanes and cyclic siloxanes.

[0030] Furthermore, the linear siloxane includes one or more of dimethyldimethoxysilane, methylphenyldimethoxysilane, diphenyldimethoxysilane, and aminopropyltrimethylsilane.

[0031] Furthermore, the cyclic siloxane includes one or more of octamethylcyclotetrasiloxane, hexamethylcyclotrisiloxane, decamethylcyclopentasiloxane, dodecylcyclohexasiloxane, trifluoropropylmethylcyclotrisiloxane, and tetramethyltetraphenylcyclotetrasiloxane.

[0032] Preferably, the organosilicon intermediate is octamethylcyclotetrasiloxane.

[0033] Furthermore, the acidic catalyst includes one or more of trifluoromethanesulfonic acid, hydrochloric acid, sulfuric acid, and cation exchange resin.

[0034] Furthermore, the cation exchange resin is a polymer compound containing a large number of strongly acidic groups, such as sulfonic acid groups (-SO3H). These groups can dissociate into hydrogen ions (H+) in aqueous solution. + This results in strong acidity. Cation exchange resins catalyze processes by donating protons or accepting electron pairs through their acidic groups.

[0035] Furthermore, the amount of the acidic catalyst added is 0.5% to 2% of the total mass of hexamethyldisiloxane, thiopropylmethyldimethoxysilane, and the organosilicon intermediate.

[0036] Furthermore, the molar ratio of hexamethyldisiloxane, thiopropylmethyldimethoxysilane and organosilicon intermediate is 1:(10-50):(40-100).

[0037] Furthermore, the molar ratio of hexamethyldisiloxane added as a capping agent affects the molecular weight of the polymer; the molar ratio of thiopropylmethyldimethoxysilane added as a grafting agent affects the thiol content of the side-thiol polysiloxane.

[0038] Furthermore, the molar ratio of the thiopropylmethyldimethoxysilane to water is 1:(0.5-1.5).

[0039] Furthermore, when the molar ratio of water to thiopropylmethyldimethoxysilane is small, the degree of hydrolysis of the organosilicon intermediate is insufficient, resulting in a low yield of side-thiol polysiloxane; when the molar ratio of water to thiopropylmethyldimethoxysilane is large, the polymer is difficult to polycondense, resulting in insufficient molecular weight, which in turn affects subsequent crosslinking and curing.

[0040] Furthermore, the time for the complete reaction is 4 to 8 hours.

[0041] Furthermore, if the reaction temperature is too low or the reaction time is too short, the hydrolysis and condensation will be insufficient, resulting in poor grafting effect of thiol groups; if the reaction temperature is too high or the reaction time is too long, the reaction will be too intense, easily leading to gelation. Under the conditions of a reaction temperature of 60-90℃ and a reaction time of 4-8h, side-thiol polysiloxanes with sufficient hydrolysis and condensation and good thiol grafting effect can be prepared.

[0042] Furthermore, the purification process includes extraction, dehydration, and distillation.

[0043] Furthermore, the extraction involves dissolving the product in dichloromethane, then adding water and ethanol, and extracting 3 to 5 times.

[0044] Furthermore, the dehydration is achieved by adding anhydrous magnesium sulfate after extraction.

[0045] Furthermore, the distillation is performed by removing water followed by vacuum distillation at 60–80°C to remove excess solvent.

[0046] Specifically, the purification process includes dissolving the product in dichloromethane, adding an appropriate amount of water and ethanol, and extracting 3 to 5 times. After extraction, anhydrous magnesium sulfate is added to remove water, and after water removal, excess solvent is removed by vacuum distillation at 60 to 80°C.

[0047] Furthermore, as an optional method for testing thiol content, the method includes the following steps:

[0048] The measurements were performed using a Bruker AVANCE III 400MHz Superconducting Fourier nuclear magnetic resonance spectrometer (Switzerland). The measurements were conducted at room temperature using deuterated chloroform (CDCl3) as the solvent. 1 The thiol content of the prepared side-thiol silicone oil can be tested by the internal standard method of HNMR.

[0049] Furthermore, the specific test method for the thiol content includes the following steps:

[0050] At room temperature, using dioxane as an internal standard and CDCl3 as a solvent, a certain amount of sample and 1,4-dioxane were mixed in CDCl3, sonicated for 20 min, and then tested to calculate the thiol content.

[0051] Furthermore, the formula for calculating the thiol content (SC) is as follows:

[0052]

[0053] In the formula, the unit of SC is mmol·g -1 A represents half the absorption peak area of ​​the -CH2- group linked to mercaptopropyl group and -SH; B represents the peak area of ​​the -CH2- group in 1,4-dioxane; W i W represents the mass of the internal standard, in grams. s 8 represents the mass of the sample in g; 8 represents the number of protons in 1,4-dioxane; 88 represents the relative molecular mass of 1,4-dioxane in g·mol⁻¹. -1 .

[0054] Furthermore, the viscosity is tested according to GB / T10247-□1988, which measures the dynamic viscosity at 25°C.

[0055] Furthermore, the side-thiol silicone oil has a thiol content of 0.5–2 mmol / g and a viscosity of 3000–8000 mPa·s.

[0056] Preferably, the side-thiol silicone oil has a thiol content of 0.8–1.2 mmol / g and a viscosity of 4000–6000 mPa·s.

[0057] Furthermore, the end-vinyl hydrogen-containing silicone oil is a polysiloxane with hydrogen-containing side chains at the vinyl end. The side-thiol silicone oil and the polysiloxane can combine curing and foaming in the same raw material. Otherwise, it is necessary to add additional vinyl silicone oil (vinyl silicone oil: a polysiloxane with vinyl end side chains all containing methyl segments) for curing, which will result in unsatisfactory cell number and uniformity. As for the vinyl content of the end-vinyl hydrogen-containing silicone oil, too little will make it difficult for the cells to cure and form or even result in no cells. Too much will result in larger cell size and fewer cells.

[0058] Furthermore, the structural formula of the end-vinyl hydrogen-containing silicone oil is:

[0059]

[0060] In the formula, x is selected from any integer from 1 to 96, and y is selected from any integer from 1 to 16.

[0061] Furthermore, as an optional approach, the method for preparing the end-vinyl hydrogen-containing silicone oil includes the following steps:

[0062] Divinyltetramethyldisiloxane, tetramethylcyclotetrasiloxane, an organosilicon intermediate, an acidic catalyst, and water are mixed and reacted thoroughly at 50–70°C. The resulting purified product is the vinyl-terminated hydrogen-containing silicone oil. The specific reaction equation is as follows:

[0063]

[0064] Furthermore, the organosilicon intermediate includes linear siloxanes and cyclic siloxanes.

[0065] Furthermore, the linear siloxane includes one or more of dimethyldimethoxysilane, methylphenyldimethoxysilane, diphenyldimethoxysilane, and aminopropyltrimethylsilane.

[0066] Furthermore, the cyclic siloxane includes one or more of octamethylcyclotetrasiloxane, hexamethylcyclotrisiloxane, decamethylcyclopentasiloxane, dodecylcyclohexasiloxane, trifluoropropylmethylcyclotrisiloxane, and tetramethyltetraphenylcyclotetrasiloxane.

[0067] Preferably, the organosilicon intermediate is octamethylcyclotetrasiloxane.

[0068] Furthermore, the acidic catalyst includes one or more of trifluoromethanesulfonic acid, hydrochloric acid, sulfuric acid, and cation exchange resin.

[0069] Furthermore, the amount of acidic catalyst added is 0.5% to 2% of the total mass of divinyltetramethyldisiloxane, tetramethylcyclotetrasiloxane, and organosilicon intermediate.

[0070] Furthermore, the molar ratio of the divinyltetramethyldisiloxane, tetramethylcyclotetrasiloxane and the organosilicon intermediate is 1:(2-10):(1-4).

[0071] Furthermore, the molar ratio of the divinyltetramethyldisiloxane added as a capping agent affects the molecular weight and vinyl content of the polymer; the tetramethylcyclotetrasiloxane is used to introduce side active hydrogen, and the molar ratio added affects the hydrogen content of the end vinyl hydrogen-containing polysiloxane.

[0072] Furthermore, the molar ratio of the tetramethylcyclotetrasiloxane to water is 1:(0.2-0.6).

[0073] Furthermore, when the molar ratio of water to tetramethylcyclotetrasiloxane is small, insufficient hydrolysis of tetramethylcyclotetrasiloxane and organosilicon intermediates is likely to occur, resulting in a low yield of end-vinyl hydrogen-containing polysiloxanes; when the molar ratio of water to tetramethylcyclotetrasiloxane is large, gelation is likely to occur.

[0074] Furthermore, the time for the complete reaction is 6 to 10 hours.

[0075] Furthermore, if the reaction temperature is too low or the reaction time is too short, the hydrolysis and condensation will be insufficient, resulting in poor grafting effect of the active hydrogen. If the reaction temperature is too high or the reaction time is too long, the reaction will be too violent and gelation will easily occur. Under the conditions of a reaction temperature of 50-70°C and a reaction time of 6-10 hours, terminal vinyl hydrogen-containing polysiloxanes with sufficient hydrolysis and condensation and good grafting effect of active hydrogen can be prepared.

[0076] Furthermore, the purification process includes extraction, dehydration, and distillation.

[0077] Furthermore, the extraction involves dissolving the product in dichloromethane, then adding water and ethanol, and extracting 3 to 5 times.

[0078] Furthermore, the dehydration is achieved by adding anhydrous magnesium sulfate after extraction.

[0079] Furthermore, the distillation is performed by removing water followed by vacuum distillation at 60–80°C to remove excess solvent.

[0080] Specifically, the purification process includes dissolving the product in dichloromethane, adding an appropriate amount of water and ethanol, and extracting 3 to 5 times. After extraction, anhydrous magnesium sulfate is added to remove water, and after water removal, excess solvent is removed by vacuum distillation at 60 to 80°C.

[0081] Furthermore, the test method for the hydrogen content of the end vinyl hydrogen-containing silicone oil is the People's Republic of China industry standard HG / T 4658-2014.

[0082] Furthermore, the test method for the vinyl content of the end-vinyl hydrogen-containing silicone oil is the People's Republic of China National Standard GB / T 43314-2023.

[0083] Preferably, the vinyl content of the end-vinyl hydrogen-containing silicone oil is 0.4-0.6 mmol / g, and the hydrogen content is 9-10 mmol / g.

[0084] Furthermore, the alcohol compound or hydroxyl silicone oil is a low molecular weight hydroxyl silicone oil with a high hydroxyl content and a low molecular weight alcohol with a high boiling point (boiling point > 90℃). For the hydroxyl content of the hydroxyl silicone oil, too little hydroxyl content will result in high system viscosity and poor dispersibility, leading to poor foaming; too much hydroxyl content will cause condensation reactions due to unstable raw materials, making it difficult to maintain a high hydroxyl content. Using low-boiling-point low molecular weight alcohols such as ethanol will cause evaporation under ultraviolet irradiation, affecting the condensation and dehydrogenation reaction of hydroxyl groups with silicon-hydrogen bonds, thus affecting the foaming effect.

[0085] Furthermore, the boiling point >90℃ refers to a boiling point >90℃ under standard atmospheric pressure (101kPa).

[0086] Preferably, the hydroxyl content of the hydroxyl silicone oil is 0.8 to 0.9 mmol / g.

[0087] Preferably, the alcohol compound is an alcohol compound with a boiling point >150°C.

[0088] Specifically, the alcohol compounds include one or more of n-propanol, ethylene glycol, and butanediol.

[0089] More preferably, the alcohol compound is ethylene glycol and / or butanediol.

[0090] Furthermore, the photoinitiators used are all commercially available free radical photoinitiators, and their dosage is the dosage commonly used in UV curing and 3D printing. Too much or too little will not have a significant impact on silicone rubber foam.

[0091] Preferably, the photoinitiator is one or more of ethyl 2,4,6-trimethylbenzoylphenylphosphonate (TPO-L), phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide (819), and 2,4,6-trimethylbenzoyl-di(p-tolyl)phosphine oxide (TMO).

[0092] More preferably, the photoinitiator is phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide.

[0093] Furthermore, the platinum catalysts are all commercially available platinum, requiring only trace amounts, and are dissolved and diluted using alkanes with high boiling points, such as 1,4-dioxane.

[0094] Furthermore, the platinum catalyst has a platinum content of 5 to 1000 ppm.

[0095] Furthermore, the platinum catalyst is selected from trimethylcyclopentadiene platinum or acetylacetonate platinum.

[0096] This invention protects a method for preparing the silicone rubber foam material, comprising the following steps:

[0097] S1. Mix side-thiol silicone oil, terminal vinyl hydrogen-containing silicone oil, hydroxyl-containing compound, photoinitiator and platinum catalyst evenly to obtain 3D printing silicone rubber precursor;

[0098] S2. Print the 3D printed silicone rubber precursor obtained in step S1, wash the printed product, and cure it under ultraviolet irradiation to obtain silicone rubber foam material.

[0099] Existing physical foaming methods for preparing silicone rubber foam mostly employ supercritical carbon dioxide foaming, which requires sophisticated equipment and involves complex preparation processes, including pressurized dissolution and blending, and depressurization foaming, requiring 2-3 hours for curing. Existing chemical foaming methods include pre-curing and post-curing processes, also requiring 2-3 hours to prepare silicone rubber foam. Compared to these methods, the photocuring method of preparing silicone rubber foam in this invention only requires 10-20 minutes of ultraviolet light irradiation, significantly shortening the preparation time and saving energy. Furthermore, this invention extends the photocuring preparation method to 3D printing technology, enriching the processing methods for silicone rubber foam and enabling customized manufacturing and macroscopic structural design, further expanding its applications.

[0100] Furthermore, in step S2, the layer thickness in the printing is set to 50–150 μm, and the exposure time is 3–6 s, preferably 3 s.

[0101] Furthermore, in step S2, the wavelength of the ultraviolet irradiation is 350–420 nm.

[0102] Furthermore, in step S2, the intensity of the ultraviolet irradiation is 1–20 mW / cm². 2 .

[0103] Furthermore, in step S2, the curing time is 10 to 20 minutes.

[0104] Compared with existing technologies, this invention has the following advantages: This invention utilizes photocuring to prepare a silicone rubber foam material using a chemical foaming method. By cleverly controlling the content and amount of reactive functional groups such as mercapto, vinyl, silanol, and hydroxyl groups, controllable foaming is achieved during the photocuring process. This control can significantly shorten the preparation time of the silicone rubber foam material and controllably adjust the pore size. The resulting silicone rubber foam material has small and dense pores, offering advantages in terms of simple and rapid preparation compared to existing physical foaming methods. Furthermore, this invention extends photocuring to 3D technology, enriching the processing methods for silicone rubber foam and enabling customized manufacturing and macroscopic structural design, further expanding its application areas. Attached Figure Description

[0105] Figure 1 The image shows the 1H NMR spectrum of the side-thiol silicone oil used in Example 1.

[0106] Figure 2 The image shows the 1H NMR spectrum of the vinyl-terminated hydrogen-containing silicone oil used in Example 1.

[0107] Figure 3 The images show the SEM morphology of the cross-sectional cells of the silicone rubber foams prepared by 3D printing in Examples 1-8.

[0108] Figure 4 SEM images of the cross-sectional pore structure of the silicone rubber foams prepared by 3D printing in Comparative Examples 1-8.

[0109] Figure 5 The image shown is a cross-sectional view of the pore structure of the silicone rubber foam prepared by 3D printing in Comparative Example 9, captured by a regular camera. Detailed Implementation

[0110] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

[0111] Unless otherwise specified, all reagents and materials used in the following examples and comparative examples are commercially available or prepared using conventional methods.

[0112] Hydroxyl silicone oils with different hydroxyl contents were all purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0113] The vinyl silicone oil was purchased from Guangzhou Jucheng Zhaoye Organosilicon Raw Material Co., Ltd.

[0114] Trimethylcyclopentadiene platinum (platinum content 1000ppm) was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0115] Photoinitiator 819 was purchased from BASF AG, Germany.

[0116] Example 1: A photocurable 3D printable silicone rubber foam material

[0117] 1. Experimental Methods

[0118] (1) Preparation of side-thiol silicone oil

[0119] Weigh 1.86 g of hexamethyldisiloxane, 72.14 g of thiopropylmethyldimethoxysilane, 296.62 g of octamethylcyclotetrasiloxane, 1.85 g of trifluoromethanesulfonic acid, and 14.4 mL of water, mix them, and then carry out a hydrolysis-condensation reaction at 80 °C for 6 h to obtain the product. Dissolve the product in dichloromethane, and then add an appropriate amount of water and ethanol for extraction three times. After extraction, add anhydrous magnesium sulfate to remove water. After water removal, remove excess solvent by vacuum distillation at 70 °C to obtain side-thiol silicone oil.

[0120] (2) Preparation of vinyl-terminated hydrogen-containing silicone oil

[0121] Weigh 20g of divinyltetramethyldisiloxane, 120.26g of tetramethylcyclotetrasiloxane, 60g of octamethylcyclotetrasiloxane, 1g of trifluoromethanesulfonic acid, and 3.6mL of water, mix them, and then carry out a hydrolysis-condensation reaction at 60℃ for 8 hours to obtain the product. Dissolve the product in dichloromethane, and then add an appropriate amount of water and ethanol for extraction three times. After extraction, add anhydrous magnesium sulfate to remove water. After water removal, remove excess solvent by vacuum distillation at 70℃ to obtain the end-vinyl hydrogen-containing silicone oil.

[0122] (3) Preparation of a photocurable 3D printable silicone rubber foam material

[0123] A photocurable 3D printable silicone rubber foam material comprises, by total mass percentage, the following components: 45.5% side-mercaptosilicone oil (mercap content 1 mmol / g, viscosity 5000 mPa·s); 50% end-vinyl hydrogen-containing silicone oil (vinyl content 0.5 mmol / g, hydrogen content 10 mmol / g); 2% hydroxyl silicone oil (hydroxyl content 0.9 mmol / g); 1.5% photoinitiator 819; and 1% UV-activated platinum catalyst trimethylcyclopentadiene platinum (platinum content 1000 ppm).

[0124] Specifically, 22.75g of side-thiol silicone oil, 25g of terminal vinyl hydrogen-containing silicone oil, 1g of hydroxyl silicone oil, 0.75g of photoinitiator 819, and 0.5g of trimethylcyclopentadiene platinum (platinum content 1000ppm) were sequentially added to a black plastic container and stirred evenly to obtain a photocurable 3D printable silicone rubber precursor. This precursor was then poured into the resin tank of a 3D printer. 3D printing tests were conducted using a Shenzhen Vistec LCD-3D printer with a 405nm LED light source and a light intensity of 5mW / cm². 2The layer thickness was set to 100 μm, and the exposure time was 3 seconds. After printing, the finished product was washed with ethanol to remove the uncured silicone rubber precursor. After removal, the finished product was post-cured in a 405 nm UV curing lamp for 15 minutes to obtain the 3D printed product.

[0125] 2. Experimental Results

[0126] The 1H NMR spectra of side-thiol silicone oil and terminal vinyl hydrogen-containing silicone oil are as follows: Figure 1 , Figure 2 As shown, the chemical shifts of each chemical bond are marked in the figure. In the two compounds, the peak area corresponding to the CH3-Si bond is the largest, consistent with the molecular formula. Changing the thiol or vinyl group content results in minimal changes to the 1H NMR spectra of the resulting side-thiol silicone oil or end-vinyl hydrogen-containing silicone oil; essentially only the peak area changes, while the peak positions remain unchanged. That is, the 1H NMR spectra of the side-thiol silicone oils with different thiol contents in other examples and comparative examples are essentially the same as the 1H NMR spectra of the side-thiol silicone oil in Example 1; the same applies to the 1H NMR spectra of the end-vinyl hydrogen-containing silicone oils with different vinyl group contents.

[0127] SEM results are as follows Figure 3 As shown, the pore size of the obtained material is less than 1 μm, which is nanoscale, and the number of pores is large and uniform.

[0128] Example 2: A photocurable 3D printable silicone rubber foam material

[0129] 1. Experimental Methods

[0130] A photocurable 3D printable silicone rubber foam material comprises, by total mass percentage, the following components: 40% side-mercaptosilicone oil (mercap content 1 mmol / g, viscosity 5000 mPa·s); 52% end-vinyl hydrogen-containing silicone oil (vinyl content 0.5 mmol / g, hydrogen content 10 mmol / g); 5% hydroxyl silicone oil (hydroxyl content 0.9 mmol / g); 1% photoinitiator 819; and 2% UV-activated platinum catalyst trimethylcyclopentadiene platinum (platinum content 1000 ppm).

[0131] Based on a total weight of 50g, each component raw material was weighed according to the above proportions, and a photocurable 3D printable silicone rubber foam material was prepared according to the method of Example 1.

[0132] 2. Experimental Results

[0133] SEM results are as follows Figure 3 As shown, compared to Example 1, Example 2 increased the amount of hydroxyl silicone oil and the amount of ultraviolet light-activated platinum catalyst, which to some extent made the foaming rate faster than that of Example 1. The resulting 3D printed silicone rubber foam material still had a pore size of less than 1 μm, which is nanoscale, and the number of pores was large and uniform.

[0134] Example 3: A photocurable 3D printable silicone rubber foam material

[0135] 1. Experimental Methods

[0136] A photocurable 3D printable silicone rubber foam material comprises, by total mass percentage, the following components: 50% side-mercaptosilicone oil (mercap content 1 mmol / g, viscosity 5000 mPa·s); 46.5% end-vinyl hydrogen-containing silicone oil (vinyl content 0.5 mmol / g, hydrogen content 10 mmol / g); 1% hydroxyl silicone oil (hydroxyl content 0.9 mmol / g); 2% photoinitiator 819; and 0.5% UV-activated platinum catalyst trimethylcyclopentadiene platinum (platinum content 1000 ppm).

[0137] Based on a total weight of 50g, each component raw material was weighed according to the above proportions, and a photocurable 3D printable silicone rubber foam material was prepared according to the method of Example 1.

[0138] 2. Experimental Results

[0139] SEM results are as follows Figure 3 As shown, compared to Example 1, Example 3 increases the amount of side mercapto silicone oil and photoinitiator in the crosslinking curing component, resulting in 3D printed silicone rubber foam material with pore sizes all less than 1 μm, which is nanoscale, and the number of pores is large and uniform.

[0140] Example 4: A photocurable 3D printable silicone rubber foam material

[0141] 1. Experimental Methods

[0142] (1) Preparation of side-thiol silicone oil

[0143] Weigh 1.63 g of hexamethyldisiloxane, 29.6 g of thiopropylmethyldimethoxysilane, 296.62 g of octamethylcyclotetrasiloxane, 1.63 g of trifluoromethanesulfonic acid, and 5.9 mL of water, mix them, and then carry out a hydrolysis-condensation reaction at 80 °C for 6 h to obtain the product. Dissolve the product in dichloromethane, and then add an appropriate amount of water and ethanol for extraction three times. After extraction, add anhydrous magnesium sulfate to remove water. After water removal, remove excess solvent by vacuum distillation at 70 °C to obtain side-thiol silicone oil.

[0144] (2) Preparation of vinyl-terminated hydrogen-containing silicone oil

[0145] Weigh 10g of divinyltetramethyldisiloxane, 120.26g of tetramethylcyclotetrasiloxane, 54g of octamethylcyclotetrasiloxane, 0.92g of trifluoromethanesulfonic acid, and 3.6mL of water, mix them, and then carry out a hydrolysis-condensation reaction at 60℃ for 8 hours to obtain the product. Dissolve the product in dichloromethane, and then add an appropriate amount of water and ethanol for extraction three times. After extraction, add anhydrous magnesium sulfate to remove water. After dehydration, remove excess solvent by vacuum distillation at 70℃ to obtain the end-vinyl hydrogen-containing silicone oil.

[0146] (3) Preparation of a curable 3D printable silicone rubber foam material

[0147] A photocurable 3D printable silicone rubber foam material comprises, by total mass percentage, the following components: 45.5% side-mercaptosilicone oil (mercap content 0.5 mmol / g, viscosity 8000 mPa·s); 50% end-vinyl hydrogen-containing silicone oil (vinyl content 0.3 mmol / g, hydrogen content 11 mmol / g); 2% hydroxyl silicone oil (hydroxyl content 1 mmol / g); 1.5% photoinitiator 819; and 1% UV-activated platinum catalyst trimethylcyclopentadiene platinum (platinum content 1000 ppm).

[0148] Based on a total weight of 50g, each component raw material was weighed according to the above proportions, and a photocurable 3D printable silicone rubber foam material was prepared according to the method of Example 1.

[0149] 2. Experimental Results

[0150] SEM results are as follows Figure 3 As shown, compared to Example 1, Example 4 reduced the content of mercapto and vinyl groups and increased the content of hydrogen and hydroxyl groups, which affected the matching degree of curing rate and foaming rate, resulting in larger pore size and micron-sized pores. The pore size is less than 100 μm and the number of pores is relatively large. It is still a silicone rubber foam material with good performance.

[0151] Example 5: A photocurable 3D printable silicone rubber foam material

[0152] 1. Experimental Methods

[0153] (1) Preparation of side-thiol silicone oil

[0154] Weigh 3.36 g of hexamethyldisiloxane, 169.3 g of thiopropylmethyldimethoxysilane, 296.62 g of octamethylcyclotetrasiloxane, 2.35 g of trifluoromethanesulfonic acid, and 33.8 mL of water, mix them, and then carry out a hydrolysis-condensation reaction at 80 °C for 6 h to obtain the product. Dissolve the product in dichloromethane, and then add an appropriate amount of water and ethanol for extraction three times. After extraction, add anhydrous magnesium sulfate to remove water. After water removal, remove excess solvent by vacuum distillation at 70 °C to obtain side-thiol silicone oil.

[0155] (2) Preparation of vinyl-terminated hydrogen-containing silicone oil

[0156] Weigh 36g of divinyltetramethyldisiloxane, 120.26g of tetramethylcyclotetrasiloxane, 90g of octamethylcyclotetrasiloxane, 1.23g of trifluoromethanesulfonic acid, and 3.6mL of water, mix them, and then carry out a hydrolysis-condensation reaction at 60℃ for 8 hours to obtain the product. Dissolve the product in dichloromethane, and then add an appropriate amount of water and ethanol for extraction three times. After extraction, add anhydrous magnesium sulfate to remove water. After water removal, remove excess solvent by vacuum distillation at 70℃ to obtain the end-vinyl hydrogen-containing silicone oil.

[0157] (3) Preparation of a curable 3D printable silicone rubber foam material

[0158] A photocurable 3D printable silicone rubber foam material comprises, by total mass percentage, the following components: 45.5% side-mercaptosilicone oil (mercap content 2 mmol / g, viscosity 3000 mPa·s); 50% end-vinyl hydrogen-containing silicone oil (vinyl content 0.8 mmol / g, hydrogen content 8 mmol / g); 2% hydroxyl silicone oil (hydroxyl content 0.6 mmol / g); 1.5% photoinitiator 819; and 1% UV-activated platinum catalyst trimethylcyclopentadiene platinum (platinum content 1000 ppm).

[0159] Based on a total weight of 50g, each component raw material was weighed according to the above proportions, and a photocurable 3D printable silicone rubber foam material was prepared according to the method of Example 1.

[0160] 2. Experimental Results

[0161] SEM results are as follows Figure 3 As shown, compared to Example 1, Example 5 increased the content of mercapto groups and vinyl groups, and decreased the content of hydrogen and hydroxyl groups, affecting the matching degree of curing rate and foaming rate, resulting in larger pore sizes and becoming micron-sized pores. Compared to Example 4, Example 5 has a faster curing rate and a slower foaming rate. As can be seen from the figure, the pore uniformity of Example 5 is better than that of Example 4.

[0162] Example 6: A photocurable 3D printable silicone rubber foam material

[0163] 1. Experimental Methods

[0164] A photocurable 3D printable silicone rubber foam material comprises, by total mass percentage, the following components: 45.5% side-mercaptosilicone oil (mercap content 1 mmol / g, viscosity 5000 mPa·s); 50% end-vinyl hydrogen-containing silicone oil (vinyl content 0.5 mmol / g, hydrogen content 10 mmol / g); 2% ethylene glycol; 1.5% photoinitiator 819; and 1% UV-activated platinum catalyst trimethylcyclopentadiene platinum (platinum content 1000 ppm).

[0165] Based on a total weight of 50g, each component raw material was weighed according to the above proportions, and a photocurable 3D printable silicone rubber foam material was prepared according to the method of Example 1.

[0166] 2. Experimental Results

[0167] SEM results are as follows Figure 3 As shown, ethylene glycol was used to replace hydroxyl silicone oil in the preparation of silicone rubber foam. Since ethylene glycol is a small molecule alcohol, it is slightly inferior to hydroxyl silicone oil in the silicone oil system. Its foaming effect is slightly worse than that of the system using hydroxyl silicone oil, but it can still successfully prepare silicone rubber foam with micron-sized pores and a large number of pores.

[0168] Example 7: A photocurable 3D printable silicone rubber foam material

[0169] 1. Experimental Methods

[0170] A photocurable 3D printable silicone rubber foam material comprises, by total mass percentage, the following components: 40% side-mercaptosilicone oil (mercap content 1 mmol / g, viscosity 5000 mPa·s); 52% end-vinyl hydrogen-containing silicone oil (vinyl content 0.5 mmol / g, hydrogen content 10 mmol / g); 5% ethylene glycol; 1% photoinitiator 819; and 2% UV-activated platinum catalyst trimethylcyclopentadiene platinum (platinum content 1000 ppm).

[0171] Based on a total weight of 50g, each component raw material was weighed according to the above proportions, and a photocurable 3D printable silicone rubber foam material was prepared according to the method of Example 1.

[0172] 2. Experimental Results

[0173] SEM results are as follows Figure 3 As shown, compared to Example 6, increasing the amount of small molecule alcohol and the amount of UV-activated platinum catalyst will, to some extent, increase the foaming rate compared to Example 6. At the same time, the higher amount of small molecule alcohol has poor compatibility with the silicone oil system, making it more prone to aggregation. This results in a larger pore size and a reduced number of cells in Example 7 compared to Example 6, and the appearance of open-cell structures (interconnected cells). However, overall, it still belongs to the category of silicone rubber foam with good uniformity, a large number of cells, and micron-sized pores.

[0174] Example 8: A 3D Printable Silicone Rubber Foam Material

[0175] 1. Experimental Methods

[0176] A photocurable 3D printable silicone rubber foam material comprises, by total mass percentage, the following components: 50% side-mercaptosilicone oil (mercap content 1 mmol / g, viscosity 5000 mPa·s); 46.5% end-vinyl hydrogen-containing silicone oil (vinyl content 0.5 mmol / g, hydrogen content 10 mmol / g); 1% ethylene glycol; 2% photoinitiator 819; and 0.5% UV-activated platinum catalyst trimethylcyclopentadiene platinum (platinum content 1000 ppm).

[0177] Based on a total weight of 50g, each component raw material was weighed according to the above proportions, and a photocurable 3D printable silicone rubber foam material was prepared according to the method of Example 1.

[0178] 2. Experimental Results

[0179] SEM results are as follows Figure 3 As shown, compared to Example 6, the amount of side mercapto silicone oil and photoinitiator was increased, which to some extent made the curing rate faster than that of Example 6. This to some extent limited the aggregation and enlargement of the bubbles (referring to the process of several small bubbles aggregating to form a large bubble), but it was still possible to prepare silicone rubber foam with good uniformity, a large number of bubbles, and micron-sized bubbles.

[0180] Comparative Example 1: A photocurable 3D printable silicone rubber foam material

[0181] 1. Experimental Methods

[0182] (1) Preparation of side-thiol silicone oil

[0183] Weigh 1.28 g of hexamethyldisiloxane, 11.2 g of thiopropylmethyldimethoxysilane, 296.62 g of octamethylcyclotetrasiloxane, 1.55 g of trifluoromethanesulfonic acid, and 2.24 mL of water, mix them, and then carry out a hydrolysis-condensation reaction at 80 °C for 6 h to obtain the product. Dissolve the product in dichloromethane, and then add an appropriate amount of water and ethanol for extraction three times. After extraction, add anhydrous magnesium sulfate to remove water. After water removal, remove excess solvent by vacuum distillation at 70 °C to obtain side-thiol silicone oil.

[0184] (2) Preparation of vinyl-terminated hydrogen-containing silicone oil

[0185] Weigh 20g of divinyltetramethyldisiloxane, 120.26g of tetramethylcyclotetrasiloxane, 60g of octamethylcyclotetrasiloxane, 1g of trifluoromethanesulfonic acid, and 3.6mL of water, mix them, and then carry out a hydrolysis-condensation reaction at 60℃ for 8 hours to obtain the product. Dissolve the product in dichloromethane, and then add an appropriate amount of water and ethanol for extraction three times. After extraction, add anhydrous magnesium sulfate to remove water. After water removal, remove excess solvent by vacuum distillation at 70℃ to obtain the end-vinyl hydrogen-containing silicone oil.

[0186] (3) Preparation of a curable 3D printable silicone rubber foam material

[0187] A photocurable 3D printable silicone rubber foam material comprises, by total mass percentage, the following components: 45.5% side-mercaptosilicone oil (mercap content 0.2 mmol / g, viscosity 10000 mPa·s); 50% end-vinyl hydrogen-containing silicone oil (vinyl content 0.5 mmol / g, hydrogen content 10 mmol / g); 2% hydroxyl silicone oil (hydroxyl content 0.9 mmol / g); 1.5% photoinitiator 819; and 1% UV-activated platinum catalyst trimethylcyclopentadiene platinum (platinum content 1000 ppm).

[0188] Based on a total weight of 50g, each component raw material was weighed according to the above proportions, and a photocurable 3D printable silicone rubber foam material was prepared according to the method of Example 1.

[0189] 2. Experimental Results

[0190] SEM results are as follows Figure 4 As shown, the pore size is less than 100 μm, but the number of pores is very small. This is because the low mercapto content results in a very poor match between the curing rate and the foaming rate. The slow curing rate and the fast foaming rate cause severe agglomeration and enlargement of the pores, resulting in a material with too few pores, large and non-uniform pore sizes.

[0191] Comparative Example 2: A photocurable 3D printable silicone rubber foam material

[0192] 1. Experimental Methods

[0193] (1) Preparation of side-thiol silicone oil

[0194] Weigh 2.38 g of hexamethyldisiloxane, 245.5 g of thiopropylmethyldimethoxysilane, 296.62 g of octamethylcyclotetrasiloxane, 2.72 g of trifluoromethanesulfonic acid, and 49 mL of water, mix them, and then carry out a hydrolysis-condensation reaction at 80 °C for 6 h to obtain the product. Dissolve the product in dichloromethane, and then add an appropriate amount of water and ethanol for extraction three times. After extraction, add anhydrous magnesium sulfate to remove water. After water removal, remove excess solvent by vacuum distillation at 70 °C to obtain side mercaptosilicone oil.

[0195] (2) Preparation of vinyl-terminated hydrogen-containing silicone oil

[0196] Weigh 20g of divinyltetramethyldisiloxane, 120.26g of tetramethylcyclotetrasiloxane, 60g of octamethylcyclotetrasiloxane, 1g of trifluoromethanesulfonic acid, and 3.6mL of water, mix them, and then carry out a hydrolysis-condensation reaction at 60℃ for 8 hours to obtain the product. Dissolve the product in dichloromethane, and then add an appropriate amount of water and ethanol for extraction three times. After extraction, add anhydrous magnesium sulfate to remove water. After water removal, remove excess solvent by vacuum distillation at 70℃ to obtain the end-vinyl hydrogen-containing silicone oil.

[0197] (3) Preparation of a curable 3D printable silicone rubber foam material

[0198] A photocurable 3D printable silicone rubber foam material comprises, by total mass percentage, the following components: 45.5% side-mercaptosilicone oil (mercap content 2.5 mmol / g, viscosity 1000 mPa·s); 50% end-vinyl hydrogen-containing silicone oil (vinyl content 0.5 mmol / g, hydrogen content 10 mmol / g); 2% hydroxyl silicone oil (hydroxyl content 0.9 mmol / g); 1.5% photoinitiator 819; and 1% UV-activated platinum catalyst trimethylcyclopentadiene platinum (platinum content 1000 ppm).

[0199] Based on a total weight of 50g, each component raw material was weighed according to the above proportions, and a photocurable 3D printable silicone rubber foam material was prepared according to the method of Example 1.

[0200] 2. Experimental Results

[0201] SEM results are as follows Figure 4 As shown, the pore size is less than 100 μm, but the number of pores is very small. This is because an excessively high thiol content will cause a significant mismatch between the curing rate and the foaming rate, making it difficult for the foaming component to foam. As a result, the material exhibits a very small number of pores, with micropores in a small area and no pores in most areas.

[0202] Comparative Example 3: A photocurable 3D printable silicone rubber foam material

[0203] 1. Experimental Methods

[0204] (1) Preparation of side-thiol silicone oil

[0205] Weigh 1.86 g of hexamethyldisiloxane, 72.14 g of thiopropylmethyldimethoxysilane, 296.62 g of octamethylcyclotetrasiloxane, 1.85 g of trifluoromethanesulfonic acid, and 14.4 mL of water, mix them, and then carry out a hydrolysis-condensation reaction at 80 °C for 6 h to obtain the product. Dissolve the product in dichloromethane, and then add an appropriate amount of water and ethanol for extraction three times. After extraction, add anhydrous magnesium sulfate to remove water. After water removal, remove excess solvent by vacuum distillation at 70 °C to obtain side-thiol silicone oil.

[0206] (2) Preparation of vinyl-terminated hydrogen-containing silicone oil

[0207] Weigh 15g of divinyltetramethyldisiloxane, 120.26g of tetramethylcyclotetrasiloxane, 264g of octamethylcyclotetrasiloxane, 2g of trifluoromethanesulfonic acid, and 3.6mL of water, mix them, and then carry out a hydrolysis-condensation reaction at 60℃ for 8 hours to obtain the product. Dissolve the product in dichloromethane, and then add an appropriate amount of water and ethanol for extraction three times. After extraction, add anhydrous magnesium sulfate to remove water. After water removal, remove excess solvent by vacuum distillation at 70℃ to obtain the end-vinyl hydrogen-containing silicone oil.

[0208] (3) Preparation of a curable 3D printable silicone rubber foam material

[0209] A photocurable 3D printable silicone rubber foam material comprises, by total mass percentage, the following components: 45.5% side-mercaptosilicone oil (mercap content 1 mmol / g, viscosity 5000 mPa·s); 50% end-vinyl hydrogen-containing silicone oil (vinyl content 0.2 mmol / g, hydrogen content 5 mmol / g); 2% hydroxyl silicone oil (hydroxyl content 0.9 mmol / g); 1.5% photoinitiator 819; and 1% UV-activated platinum catalyst trimethylcyclopentadiene platinum (platinum content 1000 ppm).

[0210] Based on a total weight of 50g, each component raw material was weighed according to the above proportions, and a photocurable 3D printable silicone rubber foam material was prepared according to the method of Example 1.

[0211] 2. Experimental Results

[0212] SEM results are as follows Figure 4 As shown, the pore size is less than 100 μm, but the number of pores is very small. This is because the low hydrogen content results in insufficient foaming components and incomplete foaming, leading to a material with too few pores and pores present in only a small portion of the material.

[0213] Comparative Example 4: A photocurable 3D printable silicone rubber foam material

[0214] 1. Experimental Methods

[0215] (1) Preparation of side-thiol silicone oil

[0216] Weigh 1.86 g of hexamethyldisiloxane, 72.14 g of thiopropylmethyldimethoxysilane, 296.62 g of octamethylcyclotetrasiloxane, 1.85 g of trifluoromethanesulfonic acid, and 14.4 mL of water, mix them, and then carry out a hydrolysis-condensation reaction at 80 °C for 6 h to obtain the product. Dissolve the product in dichloromethane, and then add an appropriate amount of water and ethanol for extraction three times. After extraction, add anhydrous magnesium sulfate to remove water. After water removal, remove excess solvent by vacuum distillation at 70 °C to obtain side-thiol silicone oil.

[0217] (2) Preparation of vinyl-terminated hydrogen-containing silicone oil

[0218] Weigh 30g of divinyltetramethyldisiloxane, 120.26g of tetramethylcyclotetrasiloxane, 16g of octamethylcyclotetrasiloxane, 0.83g of trifluoromethanesulfonic acid, and 3.6mL of water, mix them, and then carry out a hydrolysis-condensation reaction at 60℃ for 8 hours to obtain the product. Dissolve the product in dichloromethane, and then add an appropriate amount of water and ethanol for extraction three times. After extraction, add anhydrous magnesium sulfate to remove water. After water removal, remove excess solvent by vacuum distillation at 70℃ to obtain the end-vinyl hydrogen-containing silicone oil.

[0219] (3) Preparation of a curable 3D printable silicone rubber foam material

[0220] A photocurable 3D printable silicone rubber foam material comprises, by total mass percentage, the following components: 45.5% side-mercaptosilicone oil (mercap content 1 mmol / g, viscosity 5000 mPa·s); 50% end-vinyl hydrogen-containing silicone oil (vinyl content 1 mmol / g, hydrogen content 12 mmol / g); 2% hydroxyl silicone oil (hydroxyl content 0.9 mmol / g); 1.5% photoinitiator 819; and 1% UV-activated platinum catalyst trimethylcyclopentadiene platinum (platinum content 1000 ppm).

[0221] Based on a total weight of 50g, each component raw material was weighed according to the above proportions, and a photocurable 3D printable silicone rubber foam material was prepared according to the method of Example 1.

[0222] 2. Experimental Results

[0223] SEM results are as follows Figure 4 As shown, the pore size is less than 100 μm, but the number of pores is very small. This is because an excessively high hydrogen content will cause the foaming components to be too numerous and difficult to disperse fully, resulting in aggregation. Consequently, the resulting material exhibits a small number of pores, with only large-diameter pores present.

[0224] Comparative Example 5: A photocurable 3D printable silicone rubber foam material

[0225] 1. Experimental Methods

[0226] A photocurable 3D printable silicone rubber foam material comprises, by total mass percentage, the following components: 45.5% side-mercaptosilicone oil (mercap content 1 mmol / g, viscosity 5000 mPa·s); 50% end-vinyl hydrogen-containing silicone oil (vinyl content 0.5 mmol / g, hydrogen content 10 mmol / g); 2% hydroxyl silicone oil (hydroxyl content 0.3 mmol / g); 1.5% photoinitiator 819; and 1% UV-activated platinum catalyst trimethylcyclopentadiene platinum (platinum content 1000 ppm).

[0227] Based on a total weight of 50g, each component raw material was weighed according to the above proportions, and a photocurable 3D printable silicone rubber foam material was prepared according to the method of Example 1.

[0228] 2. Experimental Results

[0229] SEM results are as follows Figure 4 As shown, the pore size is less than 100 μm, but the number of pores is very small. This is because the low hydroxyl content results in insufficient foaming components and incomplete foaming, leading to a material with too few pores and pores in only a small area.

[0230] In addition, hydroxyl silicone oils with a hydroxyl content greater than 1 mmol / g are unstable and will undergo self-condensation, resulting in a decrease in hydroxyl content and making it impossible to stably prepare 3D printed silicone rubber foam materials.

[0231] Comparative Example 6: A photocurable 3D printable silicone rubber foam material

[0232] 1. Experimental Methods

[0233] A photocurable 3D printable silicone rubber foam material comprises, by total mass percentage, the following components: 40% side-mercaptosilicone oil (mercap content 1 mmol / g, viscosity 5000 mPa·s); 40% vinyl silicone oil (vinyl content 0.12 mmol / g, viscosity 5000 mPa·s); 15% terminal vinyl hydrogen-containing silicone oil (vinyl content 0.5 mmol / g, hydrogen content 10 mmol / g); 2.5% hydroxyl silicone oil (hydroxyl content 0.9 mmol / g); 1.5% photoinitiator 819; and 1% UV-activated platinum catalyst trimethylcyclopentadiene platinum (platinum content 1000 ppm).

[0234] Based on a total weight of 50g, each component raw material was weighed according to the above proportions, and a photocurable 3D printable silicone rubber foam material was prepared according to the method of Example 1.

[0235] 2. Experimental Results

[0236] SEM results are as follows Figure 4 As shown, there are almost no bubbles. This is because choosing to add extra vinyl silicone oil for curing leads to a reduction in the amount of hydrogen-containing silicone oil, making it difficult to obtain the desired number of bubbles.

[0237] Comparative Example 7: A photocurable 3D printable silicone rubber foam material

[0238] 1. Experimental Methods

[0239] A photocurable 3D printable silicone rubber foam material comprises, by total mass percentage, the following components: 35% side-mercaptosilicone oil (mercap content 1 mmol / g, viscosity 5000 mPa·s); 60% end-vinyl hydrogen-containing silicone oil (vinyl content 0.5 mmol / g, hydrogen content 10 mmol / g); 2.5% hydroxyl silicone oil (hydroxyl content 0.9 mmol / g); 1.5% photoinitiator 819; and 1% UV-activated platinum catalyst trimethylcyclopentadiene platinum (platinum content 1000 ppm).

[0240] Based on a total weight of 50g, each component raw material was weighed according to the above proportions, and a photocurable 3D printable silicone rubber foam material was prepared according to the method of Example 1.

[0241] 2. Experimental Results

[0242] SEM results are as follows Figure 4 As shown, the pore size is less than 100μm, and the number of pores is very small. This is because an excessively low amount of side-thiol silicone oil results in a very poor match between the curing rate and the foaming rate. The slow curing rate and fast foaming rate cause severe agglomeration and enlargement of the pores, resulting in a material with too few pores, large and non-uniform pore sizes.

[0243] Comparative Example 8: A photocurable 3D printable silicone rubber foam material

[0244] 1. Experimental Methods

[0245] A photocurable 3D printable silicone rubber foam material comprises, by total mass percentage, the following components: 60% side-mercaptosilicone oil (mercap content 1 mmol / g, viscosity 5000 mPa·s); 35% end-vinyl hydrogen-containing silicone oil (vinyl content 0.5 mmol / g, hydrogen content 10 mmol / g); 2.5% hydroxyl silicone oil (hydroxyl content 0.9 mmol / g); 1.5% photoinitiator 819; and 1% UV-activated platinum catalyst trimethylcyclopentadiene platinum (platinum content 1000 ppm).

[0246] Based on a total weight of 50g, each component raw material was weighed according to the above proportions, and a photocurable 3D printable silicone rubber foam material was prepared according to the method of Example 1.

[0247] 2. Experimental Results

[0248] SEM results are as follows Figure 4 As shown, there are almost no bubbles and many defects. This is because an excessive amount of side-mercaptosilicone oil will cause a significant mismatch between the curing rate and the foaming rate, making it difficult for the foaming component to foam. This results in a material with too few bubbles, with micropores in a small area and no bubbles in most areas. Comparative Example 9: A photocurable 3D printable silicone rubber foam material.

[0249] 1. Experimental Methods

[0250] A photocurable 3D printable silicone rubber foam material comprises, by total mass percentage, the following components: 45.5% side-mercaptosilicone oil (mercap content 1 mmol / g, viscosity 5000 mPa·s); 50% end-vinyl hydrogen-containing silicone oil (vinyl content 0.5 mmol / g, hydrogen content 10 mmol / g); 2% ethanol; 1.5% photoinitiator 819; and 1% UV-activated platinum catalyst trimethylcyclopentadiene platinum (platinum content 1000 ppm).

[0251] Based on a total weight of 50g, each component raw material was weighed according to the above proportions, and a photocurable 3D printable silicone rubber foam material was prepared according to the method of Example 1.

[0252] 2. Experimental Results

[0253] The foaming results of the obtained material are as follows Figure 5 As shown (taken with a regular camera), silicone rubber foam material was prepared using ethanol instead of hydroxyl silicone oil. Since ethanol is a small molecule alcohol with a low boiling point (<80℃) and is easily volatilized by heat, it affects the condensation and dehydrogenation reaction of hydroxyl groups and silicon-hydrogen bonds, resulting in a poorer foaming effect than the system using hydroxyl silicone oil, with only large-pore cells present.

[0254] As can be seen from the above, the side-thiol silicone oil used in this invention is a polysiloxane containing thiol groups on its side chains. If terminal thiol silicone oil is used, it is difficult to form a cross-linked network with terminal vinyl hydrogen-containing silicone oil. Regarding the thiol content in the thiol silicone oil, too little will make it difficult for the silicone rubber foam to cure and form (Comparative Example 1); too much will accelerate the curing speed, making the foaming process too restrictive and difficult to form small and dense cells (Comparative Example 2). Regarding the amount of side-thiol silicone oil, too little will cause severe cell aggregation and enlargement, resulting in too few cells, large and uneven pore sizes (Comparative Example 7); too much will make foaming difficult and result in an uneven number of cells (Comparative Example 8).

[0255] The vinyl-terminated hydrogen-containing silicone oil used in this invention is a polysiloxane with hydrogen-containing side chains at the vinyl end. By using side-mercapto-silicone oil in the raw materials, this polysiloxane cleverly integrates curing and foaming into a single material. If vinyl-terminated hydrogen-containing silicone oil is not used, and additional vinyl silicone oil is added for curing (Comparative Example 6), on the one hand, the amount of hydrogen-containing silicone oil used will be reduced, making it difficult to obtain the ideal number of cells; on the other hand, the crosslinking system will be too complex and dense, making it difficult to obtain uniform cells, and uneven cell distribution may occur. Specifically, regarding the vinyl content in the vinyl-terminated hydrogen-containing silicone oil, if it is too low, the silicone rubber foam will be difficult to cure and may not have cells at all (Comparative Example 3); if it is too high, the content of mercapto-silicone oil will be low, resulting in insufficient restriction of the foaming process and difficulty in forming small and dense cells (Comparative Example 4).

[0256] The alcohols used in this invention are low molecular weight hydroxyl silicone oils with high hydroxyl content and low molecular weight alcohols with high boiling points. If hydroxyl silicone oils with too low hydroxyl content are used, the system viscosity will be high and the dispersibility will be poor, resulting in poor foaming effect (Comparative Example 5). On the other hand, hydroxyl silicone oils with too high hydroxyl content have no effect on silicone rubber foaming, but there is a problem of raw material instability, which may lead to self-condensation and make it difficult to maintain a high hydroxyl content. If low-boiling-point alcohols such as ethanol are used, they may volatilize when heated during ultraviolet irradiation, affecting the foaming effect (Comparative Example 9).

[0257] The photoinitiators used in this invention are all commercially available free radical photoinitiators, and their dosage is the dosage commonly used in UV curing and 3D printing. Too much or too little will not have a significant impact on silicone rubber foam.

[0258] The ultraviolet-activated platinum used in this invention is all commercially available platinum. Due to the small amount added, it is dissolved and diluted to a mixture of 5-1000 ppm using a high-boiling-point alkane such as 1,4-dioxane for easy weighing. Too little platinum will result in a slow foaming rate, making it difficult to match with the curing rate and leading to poor foaming effect; too much platinum will not have a significant impact on silicone rubber foaming, but it will increase costs.

[0259] In summary, the photocurable 3D printable silicone rubber foam material, by mass percentage, comprises 40%–50% side-thiol silicone oil, 45%–55% terminal vinyl hydrogen-containing silicone oil, 1%–5% hydroxyl-containing compounds (hydroxyl silicone oil, n-propanol, ethylene glycol, butanediol), 1%–2% photoinitiator, and 0.5%–2% UV-activated platinum catalyst. The side-thiol silicone oil has a thiol content of 0.5–2 mmol / g; the terminal vinyl hydrogen-containing silicone oil has a vinyl content of 0.3–0.8 mmol / g and a hydrogen content of 8–11 mmol / g; the hydroxyl-containing compound is one or more of alcohols and hydroxyl silicone oils; the hydroxyl content of the hydroxyl silicone oil is 0.6–1 mmol / g; and the alcohol is an alcohol with a boiling point >90℃. Only by adhering to the above raw material ratio can a photocurable silicone rubber foam material with good uniformity and a large number of cells in the nano- or micron size be prepared.

[0260] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A silicone rubber foam material, characterized in that, It includes the following components as a percentage of total mass: 40%–50% side mercapto silicone oil; 45%–55% end vinyl hydrogen-containing silicone oil; 1%–5% hydroxyl compounds; 1%–2% photoinitiator; 0.5%–2% platinum catalyst; The side-thiol silicone oil has a thiol content of 0.5–2 mmol / g; The vinyl content of the terminal vinyl hydrogen-containing silicone oil is 0.3-0.8 mmol / g, and the hydrogen content is 8-11 mmol / g; The hydroxyl-containing compound is one or more of alcohols and hydroxyl silicone oils; The hydroxyl content of the hydroxyl silicone oil is 0.6–1 mmol / g; The alcohols mentioned are alcohols with a boiling point >90℃.

2. The silicone rubber foam material according to claim 1, characterized in that, The structural formula of the side-thiol silicone oil is: In the formula, m is selected from any integer from 1 to 400, and n is selected from any integer from 1 to 80.

3. The silicone rubber foam material according to claim 1, characterized in that, The side-thiol silicone oil has a thiol content of 0.8–1.2 mmol / g.

4. The silicone rubber foam material according to claim 1, characterized in that, The structural formula of the end-vinyl hydrogen-containing silicone oil is: In the formula, x is selected from any integer from 1 to 96, and y is selected from any integer from 1 to 16.

5. The silicone rubber foam material according to claim 1, characterized in that, The terminated vinyl hydrogen-containing silicone oil has a vinyl content of 0.4–0.6 mmol / g and a hydrogen content of 9–10 mmol / g.

6. The silicone rubber foam material according to claim 1, characterized in that, The hydroxyl content of the hydroxyl silicone oil is 0.8–0.9 mmol / g.

7. The silicone rubber foam material according to claim 1, characterized in that, The photoinitiator is one or more of ethyl 2,4,6-trimethylbenzoylphenylphosphonate, phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide, and 2,4,6-trimethylbenzoyl-di(p-tolyl)phosphine oxide.

8. The silicone rubber foam material according to claim 1, characterized in that, The platinum catalyst has a platinum content of 5 to 1000 ppm.

9. A method for preparing the silicone rubber foam material according to any one of claims 1 to 8, characterized in that, Includes the following steps: S1. Mix side-thiol silicone oil, terminal vinyl hydrogen-containing silicone oil, hydroxyl-containing compound, photoinitiator and platinum catalyst evenly to obtain 3D printing silicone rubber precursor; S2. Print the 3D printed silicone rubber precursor obtained in step S1, wash the printed product, and cure it under ultraviolet irradiation to obtain silicone rubber foam material.

10. The use of the silicone rubber foam material according to any one of claims 1 to 8 in the preparation of shock-absorbing materials, sound-insulating materials, heat-insulating materials, sealing materials or filling materials.

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