A poss-modified high dielectric constant silicone rubber composite and a method for preparing the same

Abstract

This invention discloses a POSS-modified high-dielectric-performance silicone rubber and its preparation method. The silicone rubber is made from the following raw materials: 110 rubber, modified silicone rubber, silica, ester-based POSS, and a vulcanizing agent. The addition of ester-based POSS to this composite material significantly improves the dielectric constant of the silicone rubber, while also noticeably improving the material's mechanical properties and thermal stability. The preparation process is simple and efficient, and easily scalable for mass production.

Description

Technical Field

[0001] This invention relates to a POSS-modified high dielectric constant silicone rubber and its preparation method, belonging to the field of polymer materials technology. Background Technology

[0002] Silicone rubber possesses advantages such as low modulus, high elasticity, high insulation, and low viscoelastic hysteresis loss, making it one of the ideal materials for dielectric elastomers. However, unmodified silicone rubber exhibits a low dielectric constant, requiring it to operate at higher driving voltages, which is detrimental to the practical application of dielectric elastomer transducers.

[0003] Studies have found that physical and chemical modification of silicone rubber can improve its dielectric constant. Sheima et al. started with polymethylvinylsiloxanes with different vinyl contents, and then converted the vinyl groups into polar groups of various properties (-CN, -NO2, -Cl, -OH, etc.) through an efficient one-step mercapto-ene click reaction, which significantly improved the dielectric constant of the material (Macromolecules, 2021, 54(12): 5737-5749.). Adding conductive particles to the material can improve its dielectric constant, and the effect of low-load conductive particles is very obvious. When conductive fillers are used to increase the dielectric constant of the material, when the filler reaches a threshold, it is easy to form conductive paths in the material, making the material unusable (ACS Nano, 2009, 3(9), 2447-2450.). Adding ceramic materials to materials often requires a very high content to improve the dielectric constant of the material. Moreover, ceramic materials have poor compatibility with polymer matrices, which can easily lead to filler aggregation, increase internal defects in the material, and reduce its performance (Chem.Eng.J,2020,393:124791.).

[0004] Polyhedral oligomeric silsesquioxane (POSS) is a novel nanostructured material that has emerged in recent years. Its general formula is (RSiO). 1.5In POSS, R can be hydrogen atoms, alkyl, halogen, alkenyl, aryl, or other groups. POSS is a novel high-performance hybrid material commonly used to modify various polymer systems as a nanostructure filler. Numerous studies have shown that adding POSS to a polymer matrix can improve the overall performance of composite materials, such as service temperature, decomposition temperature, oxidation resistance, surface hardening properties, mechanical properties, flame resistance, and thermal evolution properties. However, the compatibility of POSS with different matrix polymers remains a significant challenge. Changes in the organic groups on the POSS molecule can be used to control compatibility with different matrices, thus forming blends or nanocomposites. The hollow cage structure of POSS results in low density, good air permeability, and a low dielectric constant. However, by modifying POSS and then combining it with a polymer matrix, the dielectric properties of the material can be improved (CN 111187461A). Summary of the Invention

[0005] The purpose of this invention is to overcome the low dielectric properties of ordinary silicone rubber and provide a POSS-modified high dielectric constant silicone rubber and its preparation method. First, POSS and methyl vinyl silicone rubber are chemically modified, and then the two are physically modified together. The silicone rubber prepared by this method has excellent dielectric properties, as well as superior mechanical properties and thermal stability.

[0006] To achieve the above objectives, the present invention adopts the following solution:

[0007] A POSS-modified high dielectric constant silicone rubber, characterized in that it comprises 110 rubber, modified silicone rubber, silica, ester-based POSS, and a vulcanizing agent, wherein the mass fraction of the composite material is:

[0008] Element Number of parts by weight 110 glue 100 Modified silicone rubber 0-40 precipitate 3-7 Ester-based POSS 3-7 vulcanizing agent 0.3-0.5

[0009] The general structural formula of the ester-based POSS is:

[0010]

[0011] in One of them.

[0012] The 110 adhesive has a relative molecular weight of 450,000-800,000 and a vinyl content of 0.03-0.06 wt%.

[0013] The silica mentioned is one of fumed silica, precipitated silica, and silane-modified silica.

[0014] The modified silicone rubber is an ester-grafted silicone rubber, and after graft modification, the double bond content of the silicone rubber remains at 10-15 mol%.

[0015] The specific steps for preparing the modified silicone rubber are as follows: Methylvinylcyclotetrasiloxane is placed in a three-necked flask, and 0.05-0.1 wt% of tetramethylammonium hydroxide pentahydrate is added. The mixture is reacted at 95-100℃ to polymerize and obtain polymethylvinylsiloxane. The polymethylvinylsiloxane and a mercapto ester compound are dissolved in a suitable solvent and, under photoinitiator conditions, irradiated with ultraviolet light to obtain the modified silicone rubber.

[0016] The specific steps for preparing the ester-based POSS are as follows: octavinyl POSS and mercapto ester compounds are dissolved in a suitable solution, a photoinitiator is added, and the mixture is irradiated under a UV lamp. After the reaction, post-treatment is performed.

[0017] The vulcanizing agent is one of dicumyl peroxide, benzoyl peroxide, and di-tert-butyl peroxide.

[0018] The photoinitiator is one of 2,2-dimethoxy-2-phenyl-acetophenone, 2,2-diethoxy-2-phenyl-acetophenone, or 1-hydroxy-cyclohexylacetophenone.

[0019] The thiol ester compound is one of ethyl mercaptoacetate, methyl mercaptoacetate, and diethyl mercaptosuccinate.

[0020] The photoinitiator content is 0.5-2 wt%.

[0021] The ultraviolet irradiation time is 15-30 minutes.

[0022] The molar ratio of the octavinyl POSS to the mercapto ester compound is 1:9.6-12.

[0023] The molar ratio of the polymethyl vinyl silicone rubber to the mercapto ester compound is n(double bond):n(mercapto) = 1:1.3-1.5.

[0024] This invention also provides a method for preparing POSS-modified high dielectric constant silicone rubber. The specific steps are as follows: 110 rubber, modified silicone rubber, ester-based POSS, silica, and vulcanizing agent are mixed evenly on a two-roll mill. After mixing, the mixed rubber is placed on a hot press and vulcanized at 160°C for 10 minutes to obtain POSS-modified high dielectric constant silicone rubber.

[0025] Beneficial effects of the present invention

[0026] (1) The composite material provided by this invention incorporates polar POSS, which simultaneously improves the dielectric constant, thermal stability, and mechanical properties of the material. The modified silicone rubber also acts as a compatibilizer between the 110 silicone rubber and the polar POSS. This invention improves the compatibility between POSS and the polymer matrix, and the synergistic effect of POSS and modified silicone rubber in enhancing the dielectric constant of the material provides a new approach for the application of silicone rubber in the field of dielectric elastomers.

[0027] (2) The preparation process of this invention is simple, efficient, practical and easy to promote. Attached image description:

[0028] Figure 1 Dielectric constant diagrams of the embodiments and comparative examples are shown.

[0029] Figure 2 Dielectric loss diagrams of the embodiments and comparative examples are shown.

[0030] Figure 3 Mechanical performance diagrams of the embodiments and comparative examples are shown.

[0031] Figure 4 Thermal stability performance diagrams for the examples and comparative examples. Detailed implementation method:

[0032] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0033] Example

[0034] The present invention will be further described below through specific embodiments. However, these embodiments are merely exemplary and do not constitute any limitation on the scope of protection of the present invention.

[0035] Example 1

[0036] Octadecyl polysilsesquioxane and ethyl mercaptoside (n(vinyl):n(mercapto) = 1:1.5) were dissolved in a suitable amount of tetrahydrofuran, and then 1% photoinitiator DMPA was added and stirred until homogeneous. The solution was then irradiated under a UV lamp (365 nm) for 30 minutes. Part of the solution was removed using a rotary evaporator. The remaining solution was then precipitated three times with water / tetrahydrofuran to remove excess ethyl mercaptoside and photoinitiator. The precipitate was collected and dried in an oven to obtain ester-based POSS (POSS-COOR).

[0037] 50 g of V4 and 0.025 g of TMAH were added to a 250 mL three-necked flask, and the mixture was distilled under reduced pressure for half an hour. Then, 50 μL of deionized water was added, and the mixture was heated to 95 °C and reacted for 4 hours. After the reaction was complete, the mixture was washed three times with ethanol to obtain methylvinylsiloxane (PMVS). PMVS and ethyl mercaptosiloxane (n(vinyl):n(mercapto) = 1:1.5) were weighed, dissolved in THF, and 1 wt% DMPA was added. After stirring evenly, the mixture was irradiated under a UV lamp for 15 min. After the reaction was complete, the solution was concentrated using a rotary evaporator. The remaining solution was then added dropwise to an ethanol solution to precipitate three times. Finally, the white precipitate was collected and dried in an oven to obtain ethyl mercaptosiloxane-grafted methylvinylsiloxane (PMVS-g-COOR).

[0038] Preparation of POSS-modified high dielectric constant silicone rubber composite material: 100 parts of 110 rubber, 5 parts of silica, 30 parts of modified silicone rubber, 0.5 parts of dicumyl peroxide, and 3 parts of ester-based POSS were mixed evenly on a two-roll mill, and then the mixed rubber was placed on a hot press and vulcanized at 160°C for 10 minutes.

[0039] Example 2

[0040] Repeat the steps described in Example 1, except that the ester-based POSS is replaced with 5 parts.

[0041] Example 3

[0042] Repeat the steps described in Example 1, except that the ester-based POSS is replaced with 7 parts.

[0043] Comparative Example 1

[0044] Mix 100 parts of 110 rubber, 5 parts of silica, and 0.5 parts of dicumyl peroxide evenly on a two-roll mill, and then place the mixed rubber on a hot press to vulcanize at 160°C for 10 minutes.

[0045] Comparative Example 2

[0046] The preparation steps of ester-based POSS are as described in Example 1. 100 parts of 110 rubber, 5 parts of silica, 0.5 parts of dicumyl peroxide, and 3 parts of ester-based POSS are mixed evenly on a two-roll mill. Then, the mixed rubber is placed on a hot press and vulcanized at 160°C for 10 minutes.

[0047] Comparative Example 3

[0048] Repeat the steps described in Comparative Example 2, except that the ester-based POSS is replaced with 5 parts.

[0049] Comparative Example 4

[0050] Repeat the steps described in Comparative Example 2, except that the ester group POSS is replaced with 7 parts.

[0051] Comparative Example 5

[0052] The preparation steps of the modified silicone rubber are as described in Example 1. 100 parts of 110 rubber, 5 parts of silica, 15 parts of modified silicone rubber, and 0.5 parts of dicumyl peroxide are mixed evenly on a two-roll mill. Then, the mixed rubber is placed on a hot press and vulcanized at 160°C for 10 minutes.

[0053] Comparative Example 6

[0054] Repeat the steps described in Comparative Example 5, except that the modified silicone rubber is replaced with 30 parts.

[0055] Comparative Example 7

[0056] Repeat the steps described in Comparative Example 5, except that the modified silicone rubber is replaced with 40 parts.

[0057] The formulations of Examples 1-7 and Comparative Examples 1-3 of the present invention are listed in Table 1.

[0058] Table 1. Schematic diagrams of the formulations of the embodiments and comparative examples of the present invention.

[0059]

[0060]

[0061] The dielectric properties of Examples 1-3 and Comparative Examples 1-7 of the present invention are listed in Table 2.

[0062] Table 2 Comparison of dielectric properties between embodiments and comparative examples of the present invention

[0063] formula <![CDATA[Dielectric constant @ 10 -1 Hz]]> <![CDATA[Dielectric loss @ 10 -1 Hz]]> Example 1 4.74 0.06 Example 2 5.38 0.18 Example 3 5.76 0.26 Comparative Example 1 2.76 <![CDATA[3.0×10 -3 ]]> Comparative Example 2 2.94 <![CDATA[4.2×10 -3 ]]> Comparative Example 3 3.02 <![CDATA[2.0×10 -3 ]]> Comparative Example 4 3.36 <![CDATA[2.3×10 -2 ]]> Comparative Example 5 3.91 0.02 Comparative Example 6 4.52 0.09 Comparative Example 7 5.37 0.16

[0064] As shown in Table 2 above, the dielectric constants of Examples 1-3 all reached 4.5 or higher, exhibiting high dielectric constants. Comparing Examples 1-3 with Comparative Examples 1-7, it was found that POSS and modified silicone synergistically increased the dielectric constant of the materials.

[0065] The mechanical properties of Examples 1-3 and Comparative Examples 1-7 of the present invention are listed in Table 3.

[0066] Table 3 Comparison of mechanical properties between embodiments and comparative examples of the present invention

[0067]

[0068]

[0069] As shown in Table 3 above, the elongation at break of Examples 1-3 all reached over 700%, exhibiting high elongation. Comparing Examples 1-3 with Comparative Example 5, the tensile strength of the materials first increased and then decreased with the gradual addition of POSS. When the amount of POSS added was small, POSS acted as a reinforcing agent; however, with further increases in the amount of POSS, its plasticizing effect became dominant. Comparing Examples 1-3 with Comparative Examples 1-7, it was found that POSS and modified silicone had opposite effects on the elongation at break of the materials; their combination can have a complementary effect.

[0070] The thermal stability properties of Examples 1-3 and Comparative Examples 1-7 of the present invention are listed in Table 4.

[0071] Table 4 Comparison of thermal stability performance between embodiments and comparative examples of the present invention.

[0072]

[0073] As shown in Table 4 above, from Examples 1-3 and Comparative Examples 1-7, the introduction of ester groups lowers the initial decomposition temperature of the material. While the introduction of ester-based POSS groups also lowers the initial decomposition temperature, it increases other decomposition temperatures. The greater the amount of modified silica gel introduced, the higher the polymer crosslinking density and the stronger the intermolecular forces, thereby improving the thermal stability of the material.

Claims

1. A POSS-modified high dielectric constant silicone rubber composite material, characterized in that: It is composed of 110 rubber, modified silicone rubber, silica, ester-based POSS, and a vulcanizing agent. The POSS-modified high-dielectric silicone rubber is composed of the following parts by weight: 100 parts 110 rubber, 30-40 parts modified silicone rubber, 3-7 parts silica, 3-7 parts ester-based POSS, and 2-5 parts vulcanizing agent. The ester-based POSS has the following structure: ， Where R is One of them, The 110 adhesive has a relative molecular weight of 450,000-800,000 and a vinyl content of 0.03-0.06 wt%. The vulcanizing agent is one of dicumyl peroxide, benzoyl peroxide, and di-tert-butyl peroxide. The modified silicone rubber is an ester-grafted silicone rubber, and after graft modification, the double bond content of the silicone rubber remains at 10-15 mol%. The modified silicone rubber is prepared by the following method: Methylvinylcyclotetrasiloxane is placed in a three-necked flask, and 0.05-0.1 wt% of tetramethylammonium hydroxide pentahydrate is added. The mixture is reacted at 95-100℃ to polymerize and obtain polymethylvinylsiloxane. The polymethylvinylsiloxane is then dissolved with a mercapto ester compound in a suitable solvent, and under photoinitiator conditions, irradiated with ultraviolet light to obtain the modified silicone rubber. The molar ratio of polymethyl vinyl silicone rubber to mercapto ester compounds is n(double bond):n(mercapto) = 1:1.3-1.

5.

2. The high dielectric constant silicone rubber composite material according to claim 1, characterized in that, 30 parts of modified silicone rubber.

3. The high dielectric constant silicone rubber composite material according to claim 1, characterized in that, The silica mentioned is one of fumed silica, precipitated silica, and silane-modified silica.

4. The high dielectric constant silicone rubber composite material according to claim 1, characterized in that, The ester-based POSS is prepared by the following method: octavinyl POSS and a mercapto ester compound are dissolved in a suitable solution, a photoinitiator is added, and the mixture is irradiated under a UV lamp. Post-treatment is then performed after the reaction. The thiol ester compound is one of ethyl mercaptoacetate, methyl mercaptoacetate, and diethyl mercaptosuccinate. The photoinitiator is one of 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, or 1-hydroxy-cyclohexylacetophenone. The amount of photoinitiator used is 0.5-2 wt%. The UV irradiation time is 15-30 minutes.

5. The high dielectric constant silicone rubber composite material according to claim 4, characterized in that, The molar ratio of octavinyl POSS to mercapto ester compounds is 1:9.6-12.

6. A method for preparing a high dielectric constant silicone rubber composite material according to any one of claims 1-5, comprising: Mix 110 rubber, modified silicone rubber, ester-based POSS, silica, and vulcanizing agent evenly on a two-roll mill. After mixing, place the mixture on a hot press and vulcanize at 160°C for 10 minutes to obtain POSS-modified high dielectric constant silicone rubber.

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