Hydrophobic conductive liquid silicone rubber and preparation method thereof

Abstract

The invention belongs to the technical field of silicone rubber, and particularly discloses hydrophobic conductive liquid silicone rubber and a preparation method thereof. The liquid silicone rubber comprises a component A and a component B, the component A comprises addition type liquid silicone rubber base rubber and a platinum catalyst, and the component B comprises vinyl silicone oil, hydrogen-containing silicone oil, an inhibitor, a Nafion solution and fibrous silver-coated glass powder. According to the invention, fibrous silver coated glass powder is introduced into the component B as a conductive filler, and a Nafion solution is used for surface modification of the conductive filler, so that a conductive network with high efficiency and low percolation threshold is constructed, and the interfacial compatibility of the filler and a silicone rubber matrix is also significantly improved; the perfluorosulfonic acid structure of Nafion not only enhances the interaction with the silver surface, but also endows the surface of the material with the low-energy characteristic, and synergistically realizes high conductivity and high hydrophobicity. The hydrophobic conductive liquid silicone rubber disclosed by the invention not only has excellent hydrophobicity and conductivity, but also has excellent mechanical properties.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of silicone rubber, in particular to a hydrophobic conductive liquid silicone rubber and a preparation method thereof. BACKGROUND

[0002] Addition type liquid silicone rubber is a kind of high performance polymer elastomer material, which takes vinyl-containing polyorganosiloxane as the base polymer and hydrogen-containing silicone oil as the crosslinking agent, and is crosslinked and cured through the silicon hydrogen addition reaction under the catalysis of platinum catalyst. It has excellent transparency, mechanical strength, high and low temperature resistance, long-term thermal stability, biocompatibility, natural hydrophobicity and environmental aging resistance, and no small molecule by-products are released during the curing process, with low shrinkage and good dimensional stability. Therefore, liquid silicone rubber has been widely used in baby products, medical devices, electronic packaging, automobile industry and precision mold fields.

[0003] With the rapid development of microelectronic technology, flexible electronics and wearable devices, there is an urgent need for conductor materials with excellent conductive properties and environmental stability. Especially in complex environments such as moisture, sweat, rain or body fluids, electronic devices need to maintain stable electrical signal transmission capability, which puts forward double requirements of "high conductivity" and "high hydrophobicity" for the materials used for packaging or circuit formation. However, the main chain of addition type liquid silicone rubber is composed of alternating silicon-oxygen bonds (Si-O-Si), and the side chains are mainly methyl or vinyl groups, with highly saturated molecular structure and low polarity, which results in extremely low electrical conductivity of the material, seriously limiting the application of liquid silicone rubber in the electronic field.

[0004] To improve the conductive properties of liquid silicone rubber, the existing technology generally adopts the method of filling conductive fillers in the silicone rubber matrix to realize charge transmission by forming percolation network. The commonly used conductive fillers mainly include carbon-based materials such as carbon black, graphene and carbon nanotubes, and metal powders such as copper powder, silver powder, aluminum powder and zinc powder. Although these methods can improve the electrical conductivity of the composite material to a certain extent, these conductive fillers often have hydrophilicity and are easy to agglomerate, which leads to an increase in the surface energy of the composite material and a significant decrease in hydrophobicity. Moreover, the electrical conductivity of these conductive fillers is relatively limited, and a high filling amount is required to reach the percolation threshold, which further affects the flexibility and mechanical properties of the material.

[0005] Patent CN110845851A discloses a liquid conductive glue for power cable accessories and a preparation method thereof. The conductive glue comprises, by mass fraction, vinyl silicone oil, polyvinyl silicone oil, hydrogen-containing silicone oil, fumed white carbon black, conductive carbon black, hexamethyl disilazane, methyl hexadecyl dimethoxysilane, inhibitor, platinum gold catalyst and distilled water 0.5-3 parts. The liquid conductive glue prepared by the invention has a volume conductivity of 45-90 nΩ·m, a tensile strength of 4.8-7.8 Mpa and a tear strength of 25-33 N / mm. Although the liquid conductive glue has good mechanical properties and good conductivity, the hydrophobicity of the material is not mentioned, and it is difficult to meet the use requirements in complex wet environments.

[0006] Patent CN116948409A discloses a wear-resistant hydrophobic liquid silicone rubber and a preparation method thereof. The A component comprises, by weight fraction, base glue 80-100 parts, vinyl silicone oil 6-18 parts and platinum gold catalyst 0.5-0.9 parts. The B component comprises, by weight fraction, vinyl silicone oil 70-90 parts, hydrogen-containing silicone oil 17-30 parts, perfluorooctyl ethylene 10-19 parts, trimethoxysilane 15-25 parts, steel slag 10-25 parts and inhibitor 0.15-0.65 parts. The contact angle of the product is 100-111°, which significantly improves the hydrophobicity and wear resistance, but the optimization of the conductive performance is not involved.

[0007] The conductive liquid silicone rubber material in the prior art often sacrifices its intrinsic high hydrophobicity and environmental stability while achieving high conductivity, which is difficult to meet the requirements of modern electronic products. Therefore, it is urgent to develop a new type of liquid silicone rubber composite material that can have high conductivity and high hydrophobicity while maintaining the excellent flexibility, biocompatibility and environmental tolerance of silicone rubber. SUMMARY

[0008] The main purpose of the present application is to provide a hydrophobic conductive liquid silicone rubber and a preparation method thereof, which solves the problems in the above background art. The hydrophobic conductive liquid silicone rubber of the present application has good hydrophobicity, conductivity and mechanical properties.

[0009] To solve the above technical problems, the technical solution adopted by the present application is: A hydrophobic conductive liquid silicone rubber, comprising A component and B component in a mass ratio of 1:1-5, wherein the A component comprises the following raw materials in mass fraction: addition type liquid silicone rubber base glue 100-200 parts and platinum gold catalyst 1.2-3.6 parts; The B component comprises the following raw materials in mass fraction: vinyl silicone oil 50-100 parts, hydrogen-containing silicone oil 16-48 parts, inhibitor 0.5-1 parts, Nafion solution 2.5-5 parts and fibrous silver-coated glass powder 50-100 parts.

[0010] In the technical solution, the vinyl groups of the base glue and the Si-H groups of the hydrogen-containing silicone oil undergo a hydrosilylation reaction under the action of a platinum catalyst, and the inhibitor can reduce the activity of the catalyst, thereby improving the storage stability.

[0011] The application greatly improves the electrical conductivity of the liquid silicone rubber by using fibrous silver-coated glass powder as an additive and by adjusting the amount of the fibrous silver-coated glass powder. The introduction of Nafion solution increases the hydrophobicity of the liquid silicone rubber. The combination of the two improves the electrical conductivity, hydrophobicity and mechanical properties of the liquid silicone rubber.

[0012] Preferably, the addition type liquid silicone rubber is vinyl-terminated polydimethylsiloxane.

[0013] Preferably, the platinum catalyst is a complex of chloroplatinic acid and divinyltetramethyldisiloxane, and the platinum content in the catalyst is 700-9000 ppm.

[0014] Preferably, the vinyl silicone oil is one of vinyl-terminated polydimethylsiloxane or vinyl-terminated polymethylvinylsiloxane, and the viscosity of the vinyl silicone oil is 1000-60000 mpa.s, and the mass fraction of vinyl is 0.06-0.3%.

[0015] Preferably, the hydrogen-containing silicone oil is one or a mixture of more than one of hydrogen-terminated silicone oil, hydrogen-lateral silicone oil and hydrogen-terminal-lateral silicone oil, and the hydrogen content of the hydrogen-containing silicone oil is 0.5-1.0 wt%.

[0016] In the technical solution, the hydrogen-containing silicone oil is used as a crosslinking agent for liquid silicone rubber, and the content of the Si-H groups in the molecular structure of the hydrogen-containing silicone oil has a significant impact on the performance of the final product. By adjusting the proportion of the hydrogen-containing silicone oil, the number of crosslinking points and the length of the main chain in the silicone network are balanced, so that the liquid silicone rubber has the best mechanical strength. At the same time, by adjusting the proportion of the platinum catalyst and the inhibitor, the operation time and the length of the final curing time are balanced, so that the liquid silicone rubber has the best industrial efficiency.

[0017] Preferably, the inhibitor is an alkyne alcohol compound, which can reduce the activity of the platinum catalyst, prolong the storage period and operation window of the rubber compound, and improve the storage stability of the material.

[0018] Preferably, the Nafion solution is a perfluorosulfonic acid type polymer solution with a concentration of 5-20%, which enhances the hydrophobicity of the material and improves the dispersibility of the conductive filler.

[0019] Preferably, the fibrous silver-coated glass powder has a diameter of 5-20 um and a length of 100-200 um.

[0020] The second aspect of the present application provides a preparation method of the hydrophobic conductive liquid silicone rubber, comprising the following steps: (1) uniformly mixing an addition type liquid silicone rubber base glue and a platinum gold catalyst to obtain component A; (2) heating and stirring the fibrous silver-coated glass powder and a Nafion solution to obtain a mixture; (3) uniformly mixing a vinyl silicone oil, a hydrogen-containing silicone oil, an inhibitor and the mixture of step (2) to obtain component B; (4) uniformly mixing and stirring component A and component B according to a mass ratio to obtain the hydrophobic conductive liquid silicone rubber.

[0021] Preferably, the heating temperature of step (2) is 100-150℃, and the heating time is 20-40min.

[0022] In the above technical solution, the fibrous silver-coated glass powder and the Nafion solution are heated and stirred, so that the Nafion solution is adsorbed on the surface of the fibrous silver-coated glass powder. On the one hand, the dispersion effect of the fibrous silver-coated glass powder in the liquid silicone rubber and the hydrophobicity of the liquid silicone rubber can be improved. On the other hand, the unsaturated hydrogen is introduced on the surface of the fibrous silver-coated glass powder, and under the action of the platinum gold catalyst, the silicon-hydrogen addition reaction occurs with the vinyl group of the base glue, so that the fibrous silver-coated glass powder is introduced into the silicone crosslinked network, and the compatibility of the fibrous silver-coated glass powder and the liquid silicone rubber is improved, and the mechanical properties are improved.

[0023] The beneficial effects of the present application are as follows: 1. The fibrous silver-coated glass powder is used as a conductive filler in the present application, and its high aspect ratio is conducive to the formation of a continuous conductive network, which significantly reduces the percolation threshold and realizes high conductivity at a lower filling amount. The Nafion solution is introduced to pretreat the filler, the hydrophobic perfluorocarbon chain is compatible with the silicone rubber matrix, and the hydrophilic sulfonic acid group strongly interacts with the silver surface, effectively improving the dispersion and preventing agglomeration, greatly improving the interface stability, and the introduction of Nafion cooperates to construct a low surface energy interface, which improves the water resistance and realizes the synergy of high conductivity and high hydrophobicity.

[0024] 2. The liquid silicone rubber of the present application has a static contact angle of 108-110°, an electrical resistivity of 32-34nΩ·m, a tensile strength of 8.7-8.9MPa, and a tear strength of 29.4-29.7KN / m, and has excellent hydrophobicity, conductivity and mechanical properties, effectively solving the problem that the traditional liquid silicone rubber cannot simultaneously consider conductivity and hydrophobicity, and is suitable for the fields of microelectronics, flexible electronics and other fields with high requirements for material conductivity and hydrophobicity.

[0025] 3. The preparation process is simple, operable, does not require complex equipment, and is suitable for industrialized batch production. DETAILED DESCRIPTION

[0026] The technical solutions of the present application are further described below in combination with examples.

[0027] Example 1 The present example provides a hydrophobic conductive liquid silicone rubber, which comprises A component and B component with a mass ratio of 1:3, the A component comprises the following raw materials in parts by mass: addition type liquid silicone rubber base glue 150 parts, platinum gold catalyst 2.4 parts; wherein the vinyl content in the base glue is 0.34wt%; the platinum gold catalyst is a complex of chloroplatinic acid and divinyltetramethyldisiloxane, and the platinum content is 5000ppm; The B component comprises the following raw materials in parts by mass: vinyl silicone oil 80 parts, hydrogen-containing silicone oil 30 parts, inhibitor 0.7 parts, Nafion solution 3.75 parts, and fibrous silver-coated glass powder 75 parts; wherein the vinyl silicone oil is end-vinyl polydimethylsiloxane, the viscosity is 10000mPa·s, and the vinyl content is 0.12wt%; the inhibitor is 1-ethynylcyclohexanol; the hydrogen-containing silicone oil is side hydrogen-containing silicone oil, and the hydrogen content is 0.75wt%; the concentration of perfluorosulfonic acid resin in the Nafion solution is 10%, the diameter of the fibrous silver-coated glass powder is 10μm, and the length is 150μm.

[0028] The preparation method of the hydrophobic conductive liquid silicone rubber is as follows: (1) Put the addition type liquid silicone rubber base glue and the platinum gold catalyst into a vertical kneader, knead at room temperature for 30min, then open the vacuum to-0.1Mpa, continue to knead for 30min, and press the glue out to obtain the A component; (2) Stir the fibrous silver-coated glass powder and the Nafion solution at 120℃ for 30min to obtain a mixture; (3) Put the vinyl silicone oil, hydrogen-containing silicone oil, inhibitor, and the mixture of step (2) into a vertical kneader, then open the vacuum to-0.1Mpa, continue to knead for 30min, and press the glue out to obtain the B component; (4) Mix and stir the A component and the B component according to the mass ratio for 10min to obtain the hydrophobic conductive liquid silicone rubber.

[0029] Example 2 The embodiment provides a hydrophobic conductive liquid silicone rubber, which comprises an A component and a B component in a mass ratio of 1:1, the A component contains the following raw materials in parts by mass: 100 parts of addition type liquid silicone rubber base glue, 1.2 parts of platinum gold catalyst; wherein the vinyl content in the base glue is 0.34wt%; the platinum gold catalyst is a complex of chloroplatinic acid and divinyltetramethyldisiloxane, and the platinum content is 5000ppm; The B component contains the following raw materials in parts by mass: 50 parts of vinyl silicone oil, 16 parts of hydrogen-containing silicone oil, 0.5 parts of inhibitor, 3.75 parts of Nafion solution and 75 parts of fibrous silver-coated glass powder; wherein the vinyl silicone oil is end-vinyl polydimethylsiloxane, the viscosity is 10000mPa·s, and the vinyl content is 0.12wt%; the inhibitor is 1-ethynylcyclohexanol; the hydrogen-containing silicone oil is side hydrogen-containing silicone oil, and the hydrogen content is 0.75wt%; the concentration of perfluorosulfonic acid resin in the Nafion solution is 10%, the diameter of the fibrous silver-coated glass powder is 10μm, and the length is 150μm.

[0030] The preparation method of the hydrophobic conductive liquid silicone rubber is as follows: (1) the addition type liquid silicone rubber base glue and the platinum gold catalyst are placed in a vertical kneader, kneaded at room temperature for 30min, then vacuum is opened to-0.1Mpa, and the kneading is continued for 30min, and the material is pressed out to obtain the A component; (2) the fibrous silver-coated glass powder and the Nafion solution are stirred and reacted at 120℃ for 30min to obtain a mixture; (3) the vinyl silicone oil, the hydrogen-containing silicone oil, the inhibitor and the mixture of step (2) are placed in a vertical kneader, then vacuum is opened to-0.1Mpa, and the kneading is continued for 30min, and the material is pressed out to obtain the B component; (4) the A component and the B component are mixed and stirred for 10min according to the mass ratio, and the hydrophobic conductive liquid silicone rubber is obtained.

[0031] The embodiment provides a hydrophobic conductive liquid silicone rubber, which comprises an A component and a B component in a mass ratio of 1:5, the A component contains the following raw materials in parts by mass: 100 parts of addition type liquid silicone rubber base glue, 1.2 parts of platinum gold catalyst; wherein the vinyl content in the base glue is 0.34wt%; the platinum gold catalyst is a complex of chloroplatinic acid and divinyltetramethyldisiloxane, and the platinum content is 5000ppm; The B component comprises the following raw materials by mass fraction: 100 parts of vinyl silicone oil, 48 parts of hydrogen-containing silicone oil, 1 part of inhibitor, 3.75 parts of Nafion solution, and 75 parts of fibrous silver-coated glass powder; wherein the vinyl silicone oil is end-vinyl polydimethylsiloxane with a viscosity of 10,000 mPa·s and a vinyl content of 0.12 wt%; the inhibitor is 1-ethynylcyclohexanol; the hydrogen-containing silicone oil is side hydrogen-containing silicone oil with a hydrogen content of 0.75 wt%; the concentration of perfluorosulfonic acid resin in the Nafion solution is 10%, and the fibrous silver-coated glass powder has a diameter of 10 μm and a length of 150 μm.

[0032] The preparation method of the hydrophobic conductive liquid silicone rubber is as follows: (1) Put the addition type liquid silicone rubber base and platinum gold catalyst into a vertical kneader, knead at room temperature for 30 min, then open the vacuum to-0.1 Mpa, continue to knead for 30 min, and press the material to get the A component; (2) Stir the fibrous silver-coated glass powder and Nafion solution at 120°C for 30 min to obtain a mixture; (3) Put the vinyl silicone oil, hydrogen-containing silicone oil, inhibitor, and the mixture of step (2) into a vertical kneader, then open the vacuum to-0.1 Mpa, continue to knead for 30 min, and press the material to get the B component; (4) Mix and stir the A component and the B component according to the mass ratio for 10 min to obtain the hydrophobic conductive liquid silicone rubber.

[0033] Example 4: Prepare the hydrophobic conductive liquid silicone rubber according to the method of Example 1, except that the amount of fibrous silver-coated glass powder is 50 parts.

[0034] Example 5: Prepare the hydrophobic conductive liquid silicone rubber according to the method of Example 1, except that the amount of fibrous silver-coated glass powder is 100 parts.

[0035] Example 6: Prepare the hydrophobic conductive liquid silicone rubber according to the method of Example 1, except that the amount of Nafion solution is 2.5 parts.

[0036] Example 7: Prepare the hydrophobic conductive liquid silicone rubber according to the method of Example 1, except that the amount of Nafion solution is 5 parts.

[0037] Comparative Example 1: Prepare the hydrophobic conductive liquid silicone rubber according to the method of Example 1, except that the B component does not contain fibrous silver-coated glass powder.

[0038] Comparative Example 2: Hydrophobic conductive liquid silicone rubber was prepared according to the method of Example 1, except that component B did not contain Nafion solution.

[0039] Comparative Example 3: Hydrophobic conductive liquid silicone rubber was prepared according to the method of Example 1, except that component B does not contain fibrous silver-coated glass powder and Nafion solution.

[0040] The performance of the above embodiments and comparative examples was tested using the following criteria: 1. Static contact angle: The static contact angle of the prepared hydrophobic conductive liquid silicone rubber was tested in accordance with the standard GB / T30693-2014 "Measurement of the contact angle between plastic film and water".

[0041] 2. Resistivity: The resistivity of the prepared hydrophobic conductive liquid silicone rubber was tested in accordance with the standard MIL-DTL-83528C "GASKETING MATERIAL, CONDUCTIVE, SHIELDING GASKET, ELECTRONIC, ELASTOMER, MEI / RFI GENERAL SPECIFICATION FOR". The testing equipment was a DC resistance meter (CHT3540-3).

[0042] 3. Tensile strength and tear strength: The tensile strength and tear strength of the prepared hydrophobic conductive liquid silicone rubber were tested in accordance with GB / T528-2009 "Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber".

[0043] The results are shown in Table 1.

[0044] Table 1

[0045] According to Table 1, the results of Examples 1, 4, 5 and Comparative Example 1 show that adding fibrous silver-coated glass powder can significantly reduce resistivity and improve conductivity, while also improving mechanical strength to some extent. However, adding too much fibrous silver-coated glass powder can lead to agglomeration, causing defects in the liquid silicone rubber and reducing mechanical properties. This indicates that only an appropriate amount of fibrous silver-coated glass powder can achieve a simultaneous improvement in conductivity and mechanical properties.

[0046] From the results of Examples 1, 6, 7 and Comparative Example 2, it can be seen that adding Nafion solution can increase the static contact angle, improve hydrophobicity, and at the same time increase the dispersion degree of the fibrous silver-coated glass powder, thereby increasing the electron transport; while adding too much Nafion solution can form a film on the surface of the fibrous silver-coated glass powder, resulting in too high resistivity, making it difficult for electrons to transport. It is shown that lack of Nafion solution can lead to poor dispersion of fillers, strong hydrophilicity of the interface, which affects both hydrophobicity and the continuity of the conductive network, and only the appropriate amount of Nafion solution can take into account both high conductivity and high hydrophobicity.

[0047] From the results of Examples 1 and Comparative Example 3, it can be seen that pre-mixing Nafion solution and fibrous silver-coated glass powder can increase the compatibility of fibrous silver-coated glass powder in the cross-linked network of liquid silicone rubber, and improve the electron transport and mechanical strength.

[0048] The data in Table 1 show that the present application constructs an efficient conductive network by using fibrous silver-coated glass powder, and realizes the synergy of high conductivity (<35 nΩ·m), high hydrophobicity (>108°) and good mechanical properties by using Nafion solution to modify the surface of the fibrous silver-coated glass powder, which is suitable for electronic fields such as flexible electronics, sealed conductive parts, wearable devices, etc.

[0049] The above examples are only preferred technical solutions of the present application, and should not be regarded as a limitation of the present application. The protection scope of the present application should be based on the technical solutions recited in the claims, including equivalent replacement solutions of the technical features recited in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the present application.

Claims

1. A hydrophobic, electrically conductive liquid silicone rubber, characterized by: The A component and the B component are included in a mass ratio of 1:1-5, the A component includes the following raw materials in mass parts: 100-200 parts of addition type liquid silicone rubber base, 1.2-3.6 parts of platinum gold catalyst; The B component includes the following raw materials in mass parts: 50-100 parts of vinyl silicone oil, 16-48 parts of hydrogen-containing silicone oil, 0.5-1 part of inhibitor, 2.5-5 parts of Nafion solution, and 50-100 parts of fibrous silver-coated glass powder.

2. A hydrophobic, electrically conductive liquid silicone rubber according to claim 1, characterized in that: The addition type liquid silicone rubber is vinyl-terminated polydimethylsiloxane.

3. A hydrophobic, electrically conductive liquid silicone rubber according to claim 1, characterized in that: The platinum gold catalyst is a complex of chloroplatinic acid and divinyltetramethyldisiloxane, and the platinum content in the catalyst is 700-9000 ppm.

4. A hydrophobic, electrically conductive liquid silicone rubber according to claim 1, characterized in that: The vinyl silicone oil is one of vinyl-terminated polydimethylsiloxane or vinyl-terminated polymethylvinylsiloxane, and the viscosity of the vinyl silicone oil is 1000-60000 mpa.s; the vinyl mass fraction is 0.06-0.3%.

5. A hydrophobic, electrically conductive liquid silicone rubber according to claim 1, characterized in that: The hydrogen-containing silicone oil is one or a mixture of more than one of hydrogen-terminated silicone oil, hydrogen-containing side silicone oil, and end-side hydrogen-containing silicone oil, and the hydrogen content of the hydrogen-containing silicone oil is 0.5-1.0 wt%.

6. A hydrophobic, electrically conductive liquid silicone rubber according to claim 1, characterized in that: The inhibitor is an alkyne alcohol compound.

7. A hydrophobic, electrically conductive liquid silicone rubber according to claim 1, characterized by: The Nafion solution is a perfluorosulfonic acid type polymer solution, and the concentration is 5-20%.

8. A hydrophobic, electrically conductive liquid silicone rubber according to claim 1, characterized by: The fibrous silver-coated glass powder has a diameter of 5-20 um and a length of 100-200 um.

9. The process for the preparation of a hydrophobic, electrically conductive liquid silicone rubber according to any one of claims 1 to 8, characterized in that The method includes the following steps: (1) uniformly mixing the addition type liquid silicone rubber base and the platinum gold catalyst to obtain the A component; (2) heating and stirring the fibrous silver-coated glass powder and the Nafion solution to obtain a mixture; (3) uniformly mixing the vinyl silicone oil, the hydrogen-containing silicone oil, the inhibitor, and the mixture of step (2) to obtain the B component; (4) uniformly mixing and stirring the A component and the B component according to the mass ratio to obtain the hydrophobic conductive liquid silicone rubber.

10. The process for preparing a hydrophobic conductive liquid silicone rubber according to claim 9, characterized by: The heating temperature of step (2) is 100-150℃, and the heating time is 20-40 min.

Images