Preparation method of high-tensile and fast-rebound organosilicon elastomer

Abstract

The invention discloses a preparation method of a high-tensile and fast-rebound organic silicon elastomer. The preparation method specifically comprises the following steps: step 1, respectively synthesizing PDMS with molecular weights of 5000, 10000 and 20000 through a condensation polymerization reaction of silicone oil; and 2, carrying out a hydrosilylation reaction on the PDMS to generate the light-cured PDMS. According to the preparation method of the high-tensile and fast-rebound organic silicon elastomer, PDMS with the molecular weights of 5000, 10000 and 20000 is synthesized through condensation polymerization of silicone oil, then the high-tensile and fast-rebound organic silicon elastomer is prepared through hydrosilylation reaction, and the thermal stability of the material is analyzed through TG; results show that S20000-30% can obviously slow down the decomposition speed at high temperature and has good thermal stability, and the material has certain fluidity after a diluent is added to meet the viscosity requirement of a photocuring 3D printing material and has good hydrophobic performance.

Description

Technical Field

[0001] The present invention relates to the technical field of organosilicon materials, and in particular to a method for preparing a high-stretch and fast-rebound organosilicon elastomer. Background Art

[0002] The chemical structure and properties of silicone materials make them widely used in the automotive, electronics, medical and other fields. Among them, highly stretchable and soft silicone elastomers are important materials for manufacturing stretchable and soft devices. In recent years, the preparation of photocurable silicone elastomers has attracted widespread attention.

[0003] However, few studies have focused on the polymer design of silicone molecules and explored the performance of photocurable silicone elastomers under different molecular chain lengths and diluent ratios. There is an urgent need to explore the relationship between the ductility and softness of photocurable silicone elastomers and their molecular weight. Summary of the Invention

[0004] The present invention discloses a method for preparing a high-stretch and fast-rebound silicone elastomer, which aims to solve the problem raised in the background technology. However, few studies have focused on the polymer design of silicone molecules and explored the performance of photocurable silicone elastomers under different molecular chain lengths and diluent ratios. It is urgent to solve the technical problem of exploring the relationship between the ductility and softness of photocurable silicone elastomers and their molecular weight.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for preparing a high-stretch and fast-rebound silicone elastomer comprises the following steps:

[0007] Step 1: Synthesize PDMS with molecular weights of 5000, 10000, and 20000 respectively through polycondensation reaction of silicone oil;

[0008] Step 2: PDMS generates a light-curable PDMS through a hydrosilylation reaction;

[0009] In the step 1, octamethylcyclotetrasiloxane and 1,1,3,3-tetramethyldisiloxane are added to a three-necked flask with a thermometer, and after heating to 70° C., trifluoromethanesulfonic acid is added and reacted for 6 hours. After the reaction is completed, the heating is turned off, and calcium carbonate is added and stirred for 2 hours to bind the acid. After stopping stirring, the excess unreacted octamethylcyclotetrasiloxane is removed by filtration and vacuum distillation to finally obtain a hydrogen-terminated PDMS product, named S5000;

[0010] In the step 2, AMA was added to a three-necked flask, and the temperature was raised to 40° C., and then a KARSTEDT catalyst was added. Then, S5000 was slowly added dropwise. After reacting for 4 hours, 4-methoxyphenol was added to terminate the reaction, and finally, a photocurable PDMS was obtained, which was named S5000-AMA.

[0011] In a preferred embodiment, the reaction equation of S5000-AMA is:

[0012]

[0013] The preparation method of photocurable PDMS with molecular weights of 10,000 and 20,000 is the same as that of S5000-AMA.

[0014] In a preferred embodiment, the photocurable PDMS is detected by infrared spectroscopy, gel permeation chromatography, tensile testing, cyclic loading testing and creep test. When the photocurable PDMS is detected by infrared spectroscopy, there is a Si-H peak with a chemical shift of 4.6 ppm, and a methyl peak in the silicone segment is present at 0 ppm. When allyl methacrylate is added to silicon hydrogen, the Si-H peak at 4.6 ppm disappears, and a double bond peak at 5.5-6.2 ppm appears.

[0015] As can be seen from the above, a method for preparing a high-stretch and fast-rebound silicone elastomer specifically includes the following steps: Step 1: synthesizing PDMS with molecular weights of 5000, 10000 and 20000 respectively through the polycondensation reaction of silicone oil; Step 2: PDMS generates a light-cured PDMS through a hydrosilylation reaction; in the step 1, octamethylcyclotetrasiloxane and 1,1,3,3-tetramethyldisiloxane are added to a three-necked flask with a thermometer, and after heating to 70°C, trifluoromethanesulfonic acid is added and reacted for 6 hours. After completion, the heating was turned off, and calcium carbonate was added and stirred for 2 hours to bind the acid. After stopping the stirring, the excess unreacted octamethylcyclotetrasiloxane was removed by filtration and reduced pressure distillation to finally obtain a hydrogen-terminated PDMS product, named S5000. In the step 2, AMA was added to a three-necked flask, and the temperature was raised to 40° C., and then the KARSTEDT catalyst was added. Then, S5000 was slowly added dropwise, and after reacting for 4 hours, 4-methoxyphenol was added to terminate the reaction, and finally a light-cured PDMS was obtained, which was named S5000-AMA. The preparation method of the high-strength and fast-rebound silicone elastomer provided by the present invention synthesizes PDMS with molecular weights of 5,000, 10,000, and 20,000 respectively through the condensation reaction of silicone oil, and then prepares a high-strength and fast-rebound silicone elastomer through a hydrosilylation reaction. The thermal stability of the material was analyzed by TG, and the results showed that S20,000-30% can significantly slow the decomposition rate at high temperature and has good thermal stability. After adding a diluent, the material has a certain fluidity that meets the viscosity requirements of light-cured 3D printing materials and has good hydrophobic properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a preparation diagram of the photocurable PDMS for the preparation method of the high-stretch and fast-rebound silicone elastomer proposed in the present invention.

[0017] Figure 2 This is a characterization diagram of the nuclear magnetic resonance results of the preparation method of a high-stretch and fast-rebound silicone elastomer proposed in the present invention.

[0018] Figure 3 This is a molecular weight distribution diagram of the hydrogen-terminated PDMS in the preparation method of the high-stretch and fast-rebound silicone elastomer proposed in the present invention.

[0019] Figure 4 This is a diagram of the PDMS photosensitive resin curing mechanism for the preparation method of a high-stretch and fast-rebound silicone elastomer proposed in the present invention.

[0020] Figure 5 This is a diagram showing the effect of diluent on the tensile properties of photocured PDMS with different molecular weights in the preparation method of a high-stretch and fast-rebound silicone elastomer proposed in the present invention.

[0021] Figure 6 This is a creep test diagram under different pressures for the preparation method of a high-strength and fast-rebound silicone elastomer proposed in the present invention.

[0022] Figure 7 This is a rebound performance diagram of the preparation method of a high-stretch and fast-rebound silicone elastomer proposed in the present invention.

[0023] Figure 8 The contact angle and surface free energy diagrams of S20000-20%, S20000-30%, S20000-40% and S20000-50% of the preparation method of a high-stretch and fast-rebound silicone elastomer proposed by the present invention.

[0024] Figure 9 This is a thermogravimetric experimental diagram of S20000-30% of the preparation method of a high-stretch and fast-rebound silicone elastomer proposed in the present invention.

[0025] Figure 10 This is a diagram of the S20000-30% light-cured strap for the preparation method of a high-stretch and fast-rebound silicone elastomer proposed in the present invention. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0027] Reference Figures 1-10 A method for preparing a high-strength and fast-rebound silicone elastomer, taking the preparation of 5000 molecular weight photocurable PDMS as an example, the preparation steps are as follows:

[0028] 500g (1.69mol) of octamethylcyclotetrasiloxane and 12.94g (96.3mmol) of

[0029] 1,1,3,3-Tetramethyldisiloxane was added to a three-necked flask equipped with a thermometer. After heating to 70°C, 0.50 g (0.10 wt%) of trifluoromethanesulfonic acid was added and reacted for 6 h. After the reaction was completed, the heat was turned off and 1 g (0.20 wt%) of calcium carbonate was added and stirred for 2 h to bind the acid. After stirring was stopped, the mixture was filtered and the excess unreacted octamethylcyclotetrasiloxane was removed by vacuum distillation to obtain 502 g of hydrogen-terminated PDMS product, named S5000, with a yield of 98%.

[0030] The reaction equation is as follows Figure 1As shown, 2.50 g (0.02 mol) of AMA was added to a three-necked flask, and after heating to 40°C, 0.10 g (10 ppm) of KARSTEDT catalyst was added, and then 50 g (0.01 mol) of S5000 was slowly added dropwise. After reacting for 4 hours, 0.1 wt% of 4-methoxyphenol was added to terminate the reaction, and finally photocurable PDMS was obtained and named S5000-AMA. The preparation method of photocurable PDMS with molecular weights of 10,000 and 20,000 was the same as that of S5000-AMA.

[0031] In a preferred embodiment, the NMR results are as follows Figure 2 As shown:

[0032] use 1 The structures of S5000, S10000, S20000, S5000-AMA, S10000-AMA and S20000-AMA were characterized by HNMR. It was found that S5000, S10000 and S20000 had a Si-H peak at a chemical shift of 4.6 ppm, and a methyl peak in the silicone segment at 0 ppm. By calculating the peak area, the molecular weights of S5000, S10000 and S20000 were very close to the designed amounts. In addition, the molecular weight of the products was further verified by GPC.

[0033] In a preferred embodiment, as shown in the attached Figure 3 As shown:

[0034] The molecular weight of the product is basically consistent with the designed amount. Then, when allyl methacrylate is added with silicon hydrogen, the Si-H peak at 4.6 ppm disappears, and then the double bond peak at 5.5-6.2 ppm appears, which indicates the success of silicon hydrogen addition.

[0035] In a preferred embodiment, the prepared S5000-AMA and IBOA are mixed in mass ratios of 8:2, 7:3, 6:4, and 5:5, respectively, and 1 wt% TPO-L is added and stirred uniformly. The 8:2 compounded silicone photosensitive resin is named S5000-20%. Similarly, the silicone photosensitive resins compounded in 7:3, 6:4, and 5:5 ratios are named S5000-30%, S5000-40%, and S5000-50%, respectively. The same naming applies to the photosensitive resins compounded with S10000-AMA and S20000-AMA and IBOA.

[0036] The curing mechanism is as follows Figure 4As shown, TPO-L was selected as the photoinitiator because PDMS has poor compatibility with initiators such as TPO, initiator 819, and initiator 184. Only TPO-L can be well dissolved in PDMS. The prepared PDMS photosensitive resin was cured under 405nm light and its performance was tested.

[0037] In a preferred embodiment, the present application explores the effect of molecular weight on the mechanical properties of photocurable PDMS by varying the PDMS molecular chain length. The results show that at low diluent content (≥30 wt% IBOA), the tensile strength increases with increasing silicone segments; at high diluent content (<30 wt% IBOA), the tensile strength decreases with increasing silicone segments.

[0038] This is because at low diluent content, short-chain PDMS cannot show good toughness, resulting in excessive cross-linking density, the material showing the characteristics of being extremely easy to break, and reduced strength. Therefore, the longer the molecular chain, the higher the strength. Therefore, short-chain PDMS can effectively reduce the cross-linking density and improve the strength of the material after adding diluent. In addition, as the silicone chain segment increases, the tensile modulus continues to decrease and the elongation at break continues to increase, which shows that increasing the silicone chain length is helpful to improve the flexibility of the material.

[0039] In a preferred embodiment, referring to the attached Figure 5 As shown:

[0040] This application uses IBOA as a diluent. Results show that the addition of the diluent significantly improves the mechanical properties of photocurable PDMS. Neither pure photocurable PDMS nor pure IBOA has good mechanical properties. This shows that IBOA plays a significant role in improving the performance of photocurable PDMS. The performance of S5000-AMA continues to improve with the addition of IBOA, while the strength of S10000-AMA and S20000-AMA increases with the addition of IBOA, but the elongation at break initially increases and then decreases. Therefore, there is a reasonable value for the addition of IBOA. When the addition is around 30%, S20000-30% exhibits the highest elongation at break.

[0041] In a preferred embodiment, referring to the attached Figure 6 As shown:

[0042] In the cyclic loading experiment, the smaller the area of ​​the interval enclosed by the spline when it is stretched and rebounded, the better the elasticity. The experimental results show that the longer the silicone molecular chain, the better the rebound performance, and the less diluent IBOA, the better the rebound performance. Therefore, S20000-20% has the best rebound resilience. Considering both rebound resilience and elongation at break, S20000-30% has the best mechanical properties (455.65% elongation at break and excellent rebound performance). In this regard, creep tests were also carried out to further verify the rebound resilience of S20000-20%. Under a stress of 0.08MPa, S20000-30% underwent a strain of 11.8%, and its length recovery rate reached 94%, which also proved that S20000-30% has excellent rebound performance.

[0043] In a preferred embodiment, referring to the attached Figure 7 As shown:

[0044] After being stretched, S20000-30% can immediately return to its original shape. Therefore, this material has excellent rebound properties. The viscosity of the prepared PDMS photosensitive resin and the corresponding raw materials was tested. Referring to the table below, it can be seen that the larger the molecular weight, the greater the viscosity of the material. However, the viscosity of S20000-AMA has reached 1400cps, which shows that molecular weight has a significant impact on viscosity. Fortunately, the viscosity of S20000-AMA decreased significantly after adding 20wt% IBOA. When 30wt% IBOA was added, the viscosity of S20000-30% was 650cps, which meets the requirements of light-curing 3D printing.

[0045] Samples Viscosity(cps) Samples Viscosity(cps) S5000 55 S5000-50％ 50 S10000 270 S10000-20％ 360 S20000 840 S10000-30％ 250 S5000-AMA 150 S10000-40％ 150 S10000-AMA 510 S10000-50％ 140 S20000-AMA 1400 S20000-20％ 850 S5000-20％ 95 S20000-30％ 650 S5000-30％ 90 S20000-40％ 420 S5000-40％ 55 S20000-50％ 300

[0046] In a preferred embodiment, referring to the attached Figure 8 As shown:

[0047] The contact angle and surface free energy were used to study the hydrophobicity of the material. The addition of 20-50wt% diluent to S20000-AMA had little effect on the hydrophobicity of the material. The contact angle was above 110°, meeting the requirement for hydrophobic materials (contact angle ≥ 90°). This is because the silicone skeleton can increase the contact angle of the material and reduce the surface free energy of the material. The above results show that the light-cured PDMS has good hydrophobic properties.

[0048] In a preferred embodiment, referring to the attached Figure 9 As shown:

[0049] S20000-30% begins to decompose rapidly at 305°C. Subsequently, during the thermal decomposition process, the silicone material forms a protective Si-O-Si layer on its surface, preventing further decomposition. Consequently, the decomposition rate is significantly slowed, and ultimately, at 800°C, 9.7% residual carbon remains.

[0050] In a preferred embodiment, referring to the attached Figure 10 As shown:

[0051] The watchband mold was printed using LCD technology. Finally, S20000-30% was poured into the mold and the light-cured watchband was prepared. The material's excellent resilience ensured a secure fit for the sports watch, while the soft silicone material provided excellent comfort.

[0052] Working principle: When used, PDMS with molecular weights of 5000, 10000 and 20000 are synthesized through the polycondensation reaction of silicone oil, and then a light-curing PDMS is developed through the hydrosilylation reaction. The effects of different molecular weights and diluents on light-curing PDMS are studied. The results show that the light-curing PDMS has good compatibility with IBOA and TPO-L. In addition, the larger the molecular weight of the light-curing PDMS, the easier it is to stretch the cured product. However, when no diluent is added, the material performance is extremely poor. Therefore, the effect of the diluent on the light-curing PDMS is relatively small. When the diluent content is 30%, the material exhibits excellent mechanical properties and rebound performance, especially for S20000-30%, the material has fast rebound elasticity. The thermal stability of the material was analyzed by TG. The results showed that S20000-30% can significantly slow down the decomposition rate at high temperature and has good thermal stability. In addition, the viscosity and hydrophobicity of the material were also investigated. After adding the diluent, the material has a certain fluidity that meets the viscosity requirements of light-curing 3D printing materials, and has good hydrophobicity, and is expected to be used in the field of flexible wearable devices.

[0053] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing a high-strength and fast-rebound silicone elastomer, characterized in that: The specific steps include: Step 1: Synthesize PDMS with molecular weights of 5000, 10000, and 20000 respectively through polycondensation reaction of silicone oil; Step 2: PDMS generates a light-curable PDMS through a hydrosilylation reaction; In the step 1, octamethylcyclotetrasiloxane and 1,1,3,3-tetramethyldisiloxane are added to a three-necked flask with a thermometer, and after heating to 70° C., trifluoromethanesulfonic acid is added and reacted for 6 hours. After the reaction is completed, the heating is turned off, and calcium carbonate is added and stirred for 2 hours to bind the acid. After stopping stirring, the excess unreacted octamethylcyclotetrasiloxane is removed by filtration and vacuum distillation to finally obtain a hydrogen-terminated PDMS product, named S5000; In the step 2, AMA was added to a three-necked flask, and the temperature was raised to 40° C., and then a KARSTEDT catalyst was added. Then, S5000 was slowly added dropwise. After reacting for 4 hours, 4-methoxyphenol was added to terminate the reaction, and finally, a photocurable PDMS was obtained, which was named S5000-AMA.

2. The method for preparing a high-strength and fast-rebound silicone elastomer according to claim 1, characterized in that: The specific reaction equations of step one and step two are:

3. The method for preparing a high-strength and fast-rebound silicone elastomer according to claim 1, characterized in that: The photocurable PDMS is tested by infrared spectroscopy, gel permeation chromatography, tensile testing, cyclic loading testing and creep testing.

4. The method for preparing a high-strength and fast-rebound silicone elastomer according to claim 3, characterized in that: When infrared spectroscopy was used to detect the photocured PDMS, there was a Si-H peak with a chemical shift of 4.6 ppm, and a methyl peak in the silicone segment at 0 ppm. When allyl methacrylate was added to silicon hydrogen, the Si-H peak at 4.6 ppm disappeared, and a double bond peak at 5.5-6.2 ppm appeared.

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