Process for preparing graphene-doped silicone rubber foam through supercritical foaming and silicone rubber foam

Abstract

The invention discloses a process for preparing graphene doped silicone rubber foam through supercritical foaming and silicone rubber foam, the process comprises the following steps: S1, adding methyl vinyl silicone rubber, fumed silica, hydroxyl silicone oil and reduced graphene oxide into an internal mixer, mixing while heating, and aging at normal temperature to obtain a rubber compound 1; s2, adding the rubber compound 1 and a vulcanizing agent into an internal mixer, and mixing at normal temperature to obtain a rubber compound 2; s3, the rubber compound 2 is placed in a press vulcanizer to be pre-vulcanized, and a to-be-foamed product is obtained; and S4, putting the to-be-foamed product into a supercritical foaming device for foaming, then heating and drying foam obtained after foaming, and then carrying out heat treatment to obtain the final graphene-doped silicone rubber foam. According to the invention, many defects in the prior art are successfully overcome, the silicone rubber foam with high strength, good thermal conductivity, excellent buffer performance, low density, high hardness and environmental friendliness is prepared, and the silicone rubber foam has a wide application prospect.

Description

Technical Field

[0001] The invention relates to the field of silicone rubber foam materials, and in particular to a process for preparing graphene-doped silicone rubber foam by supercritical foaming and the silicone rubber foam. Background Art

[0002] With the continuous development of material science and technology, foam materials have a wide range of application needs in many fields. Silicone rubber foam has become a commonly used foam material due to its good flexibility, weather resistance and insulation properties. However, the silicone rubber foam obtained by traditional preparation methods still needs to be improved in some aspects, such as its strength, thermal conductivity and cushioning performance.

[0003] Among the many improved methods, supercritical foaming technology has received widespread attention in recent years. Supercritical fluid microporous foaming technology is a method of preparing microporous structural materials by using the dependence of the solubility of gas in polymers on pressure and temperature. Supercritical fluids have unique properties. Their density, diffusion coefficient, solvation capacity and other properties are very sensitive to changes in temperature and pressure. The viscosity and diffusion coefficient are closer to gases, while the density and solvation capacity are closer to liquids. This technology has been applied in the foaming of some polymer materials and has achieved good results.

[0004] At the same time, as a new type of two-dimensional material, graphene has excellent mechanical properties, high thermal conductivity and good electrical properties. Doping graphene into silicone rubber is expected to further improve the performance of silicone rubber foam. Studies have attempted to compound graphene with silicone rubber, but there are some problems in the preparation process, such as uneven dispersion of graphene in silicone rubber, which affects the performance improvement of the composite material.

[0005] The traditional preparation methods of silicone rubber foam mainly include chemical foaming method and physical foaming method. The chemical foaming method produces gas by decomposing the chemical foaming agent during heating to make the silicone rubber foam. The physical foaming method introduces gas, such as nitrogen, air, etc., into the silicone rubber to make it expand and form bubbles during heating. Although these two methods are easy to operate, they have the following problems:

[0006] Uneven cell structure: The chemical blowing agent is unevenly distributed in the silicone rubber, resulting in different cell sizes, affecting the overall performance of the foam.

[0007] The pore size is large: The pore size of the foam prepared by the traditional method is large, and it is difficult to achieve a microporous structure, which affects the mechanical and thermal properties of the foam.

[0008] Environmental pollution: Chemical foaming agents may produce harmful substances during the decomposition process, causing environmental pollution.

[0009] Therefore, it is necessary to improve the existing technology to provide a more reliable solution. Summary of the invention

[0010] The technical problem to be solved by the present invention is to provide a process for preparing graphene-doped silicone rubber foam by supercritical foaming and silicone rubber foam in view of the deficiencies in the above-mentioned prior art. The present invention aims to provide a method for preparing graphene-doped silicone rubber foam by supercritical foaming, and to prepare silicone rubber foam with high strength, good thermal conductivity and excellent cushioning performance by optimizing the supercritical foaming process and improving the graphene doping method.

[0011] To achieve the above object, the technical solution adopted by the present invention is: In a first aspect of the present invention, a process for preparing graphene-doped silicone rubber foam by supercritical foaming is provided, comprising the following steps:

[0012] S1. Mixing:

[0013] Adding methyl vinyl silicone rubber, fumed silica, hydroxy silicone oil and reduced graphene oxide into an internal mixer, mixing under heating, and then aging at room temperature to obtain a rubber mixture 1;

[0014] S2. Vulcanizing agent mixing:

[0015] Adding the rubber mix 1 and the vulcanizing agent into an internal mixer, and mixing at room temperature to obtain the rubber mix 2;

[0016] S3, pre-vulcanization:

[0017] The mixed rubber 2 is placed in a flat vulcanizer for pre-vulcanization to obtain a product to be foamed;

[0018] S4, Supercritical Foaming:

[0019] The product to be foamed is placed in a supercritical foaming device for foaming, and then the foam obtained after foaming is heated and dried, and then heat-treated to obtain the final graphene-doped silicone rubber foam.

[0020] Preferably, the reduced graphene oxide in step S1 is partially reduced graphene oxide with a reduction degree of 60-90%.

[0021] Preferably, step S1 specifically comprises:

[0022] Methyl vinyl silicone rubber, fumed silica, hydroxy silicone oil and partially reduced graphene oxide are sequentially added into an internal mixer at 60-100° C. in a mass ratio of 100:25:8:0.5-10, mixed at a speed of 50-200 r / min for 15-60 min, and aged at room temperature for 12-48 h to obtain a rubber mixture 1.

[0023] Preferably, the vulcanizing agent in step S2 is vulcanizing agent DCP.

[0024] Preferably, step S2 specifically comprises:

[0025] The rubber mix and the vulcanizing agent DCP were added into an internal mixer at a mass ratio of 100:1-5, and mixed at room temperature for 5-30 minutes at a rotation speed of 30-150 r / min to obtain a rubber mix 2.

[0026] Preferably, step S3 specifically comprises:

[0027] The rubber compound 2 is placed in a flat vulcanizer at 100-130° C. for pre-vulcanization, with the pre-vulcanization time being 3-25 minutes, to obtain a product to be foamed.

[0028] Preferably, the supercritical fluid used in the supercritical foaming device in step S4 is any one of supercritical carbon dioxide, supercritical nitrogen and supercritical butane.

[0029] Preferably, step S4 is specifically:

[0030] The obtained sample is placed in a supercritical carbon dioxide foaming test device and foamed at a foaming pressure of 5-25 MPa. The foam obtained after foaming is then dried at 130-180° C. for 15-60 min, and then heated to 230-280° C. for heat treatment for 15-60 min to obtain the final graphene-doped silicone rubber foam.

[0031] Preferably, the process for preparing graphene-doped silicone rubber foam by supercritical foaming comprises the following steps:

[0032] S1. Mixing:

[0033] Methyl vinyl silicone rubber, fumed silica, hydroxy silicone oil, and partially reduced graphene oxide with a reduction degree of 80% were added into an internal mixer at 80° C. in a mass ratio of 100:25:8:5, mixed at a speed of 90 r / min for 30 min, and aged at room temperature for 24 h to obtain a rubber mixture 1;

[0034] S2. Vulcanizing agent mixing:

[0035] The rubber mix and the vulcanizing agent DCP were added into an internal mixer at a mass ratio of 100:2.5, and mixed at room temperature for 10 min at a speed of 60 r / min to obtain a rubber mix 2;

[0036] S3, pre-vulcanization:

[0037] The mixed rubber 2 is placed in a mold with a length×width×thickness of 20 mm×20 mm×2 mm, and placed in a flat vulcanizer at 120° C. for pre-vulcanization. The pre-vulcanization time is 3-25 min to obtain a product to be foamed;

[0038] S4, Supercritical Foaming:

[0039] The product to be foamed is placed in a supercritical foaming device, supercritical dioxide is used as the supercritical fluid, and foaming is carried out under a pressure of 10 MPa for 3 hours. The foam obtained after foaming is then placed in a constant temperature forced air drying oven at 150°C and dried for 30 minutes, and then the temperature is raised to 250°C and heat treated for 0.5 hours to obtain the final graphene-doped silicone rubber foam.

[0040] A second aspect of the present invention provides a graphene-doped silicone rubber foam, which is prepared by the process described above.

[0041] The beneficial effects of the present invention are:

[0042] The present invention provides a process for preparing graphene-doped silicone rubber foam by supercritical foaming and graphene-doped silicone rubber foam prepared based on the process. The silicone rubber foam prepared by the present invention has the following advantages:

[0043] 1. High strength

[0044] The silicone rubber foam prepared by the invention has significantly improved strength, especially outstanding performance in tensile strength and compressive strength.

[0045] In the present invention, graphene has excellent mechanical properties, and its high modulus and high strength characteristics can effectively enhance the mechanical properties of silicone rubber foam.

[0046] In the present invention, a uniform and fine cell structure can be prepared by supercritical carbon dioxide foaming, which further improves the mechanical properties of the foam and enables it to better disperse stress when subjected to external force.

[0047] 2. Good thermal conductivity

[0048] The silicone rubber foam prepared by the invention has significantly improved thermal conductivity, and its thermal conductivity coefficient is significantly better than that of traditional silicone rubber foam.

[0049] In the present invention, graphene has extremely high thermal conductivity, and its uniform dispersion in silicone rubber can significantly improve the thermal conductivity of the foam, which is beneficial to the effective conduction and dissipation of heat.

[0050] In the present invention, the cell structure prepared by supercritical foaming technology is more uniform and fine, which reduces the resistance in the heat transfer process and further improves the thermal conductivity.

[0051] 3.Excellent cushioning performance

[0052] The silicone rubber foam prepared by the present invention has significantly improved cushioning performance, significantly reduced compression permanent deformation, and can provide better shock absorption and cushioning effects.

[0053] In the present invention, the addition of graphene makes the pore structure more uniform, improves the elastic recovery ability of the foam, and reduces the permanent deformation after compression.

[0054] In the present invention, the cell structure prepared by supercritical foaming technology is more uniform and fine, which improves the elasticity and cushioning performance of the foam, so that it can better absorb energy and restore its original shape when impacted.

[0055] 4. Low density

[0056] The silicone rubber foam prepared by the invention has a lower apparent density and is obviously lightweight.

[0057] In the present invention, the addition of graphene makes the pore structure more uniform, reduces the gaps between the pores, and reduces the overall density of the foam.

[0058] In the present invention, by precisely controlling the foaming pressure and temperature, a uniform and fine cell structure can be prepared, further reducing the density of the foam.

[0059] 5. High hardness

[0060] The silicone rubber foam prepared by the present invention has significantly improved hardness and can better resist external pressure and deformation.

[0061] In the present invention, the high modulus property of graphene significantly improves the hardness of the foam, which can better resist external pressure.

[0062] In the present invention, the cell structure prepared by supercritical foaming technology is more uniform and dense, thereby improving the overall hardness of the foam.

[0063] 6. Environmental friendliness

[0064] The invention adopts supercritical carbon dioxide foaming technology, avoids the use of traditional chemical foaming agents, and has good environmental friendliness.

[0065] In the present invention, supercritical carbon dioxide foaming technology: supercritical carbon dioxide is a green and environmentally friendly foaming agent, does not produce harmful substances, and meets the requirements of green manufacturing.

[0066] The present invention does not contain chemical foaming agents, thus avoiding the generation of harmful substances that may be produced during the decomposition process of traditional chemical foaming agents and reducing pollution to the environment.

[0067] In summary, through the optimization and improvement of the above-mentioned technical means, the present invention successfully overcomes many shortcomings of the prior art and prepares silicone rubber foam with high strength, good thermal conductivity, excellent cushioning performance, low density, high hardness and environmental friendliness; these advantages make the present invention have broad application prospects in the fields of transportation, petrochemical industry, electronics industry, aerospace and military weapons and equipment. DETAILED DESCRIPTION

[0068] The present invention is further described in detail below in conjunction with embodiments so that those skilled in the art can implement the invention with reference to the description.

[0069] It should be understood that the terms such as “having”, “including” and “comprising” used herein do not exclude the existence or addition of one or more other elements or combinations thereof.

[0070] The test methods used in the following examples are conventional methods unless otherwise specified. The materials and reagents used in the following examples are all commercially available unless otherwise specified. In the following examples, if no specific conditions are specified, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used, if the manufacturer is not specified, are all conventional products that can be purchased commercially.

[0071] The present invention provides a process for preparing graphene-doped silicone rubber foam by supercritical foaming, comprising the following steps:

[0072] S1. Mixing:

[0073] Adding methyl vinyl silicone rubber, fumed silica, hydroxy silicone oil and reduced graphene oxide into an internal mixer, mixing under heating, and then aging at room temperature to obtain a rubber mixture 1;

[0074] S2. Vulcanizing agent mixing:

[0075] Adding the rubber mix 1 and the vulcanizing agent into an internal mixer, and mixing at room temperature to obtain the rubber mix 2;

[0076] S3, pre-vulcanization:

[0077] The mixed rubber 2 is placed in a flat vulcanizer for pre-vulcanization to obtain a product to be foamed;

[0078] S4, Supercritical Foaming:

[0079] The product to be foamed is placed in a supercritical foaming device for foaming, and then the foam obtained after foaming is heated and dried, and then heat-treated to obtain the final graphene-doped silicone rubber foam.

[0080] In a preferred embodiment, the reduced graphene oxide in step S1 is partially reduced graphene oxide with a reduction degree of 60-90%, more preferably partially reduced graphene oxide with a reduction degree of 80%. The increase in the reduction degree will increase the electrical conductivity and thermal conductivity of graphene, thereby further improving the thermal conductivity and mechanical properties of the foam.

[0081] The particle size of the reduced graphene oxide can be 10-200 nm, for example, graphene nanosheets of 10 nm, 50 nm, 100 nm, and 200 nm, respectively. Graphene nanosheets with smaller particle sizes are easier to disperse evenly in silicone rubber, which helps to improve the mechanical properties and thermal conductivity of the foam.

[0082] In a preferred embodiment, step S1 specifically comprises: adding methyl vinyl silicone rubber, fumed silica, hydroxy silicone oil, and partially reduced graphene oxide in a mass ratio of 100:25:8:0.5-10 to a 60-100° C. internal mixer, mixing at a speed of 50-200 r / min for 15-60 min, and aging at room temperature for 12-48 h to obtain a rubber mixture 1.

[0083] In a preferred embodiment, the vulcanizing agent in step S2 is vulcanizing agent DCP.

[0084] In a preferred embodiment, step S2 specifically comprises: adding the rubber mix and the vulcanizing agent DCP into an internal mixer at a mass ratio of 100:1-5, and mixing at a speed of 30-150 r / min at room temperature for 5-30 min to obtain the rubber mix 2.

[0085] In a preferred embodiment, step S3 specifically includes: placing the rubber mixture 2 in a flat vulcanizer at 100-130° C. for pre-vulcanization, with the pre-vulcanization time being 3-25 minutes, to obtain a product to be foamed.

[0086] Increasing the pre-vulcanization temperature may accelerate the vulcanization reaction, making the pore structure more uniform, thereby improving the mechanical properties and thermal conductivity of the foam. Prolonging the pre-vulcanization time may make the vulcanization reaction more complete, making the pore structure more stable, thereby improving the mechanical properties and thermal conductivity of the foam.

[0087] In a preferred embodiment, the supercritical fluid used in the supercritical foaming device in step S4 is any one of supercritical carbon dioxide, supercritical nitrogen, and supercritical butane, and is more preferably supercritical carbon dioxide. The solubility and diffusion coefficient of nitrogen are different from those of carbon dioxide, which may have different effects on the pore structure and foam properties, but a uniform pore structure can still be prepared. The solubility and diffusion coefficient of butane are higher, and a finer pore structure may be prepared, thereby further improving the mechanical properties and thermal conductivity of the foam.

[0088] In a preferred embodiment, step S4 is specifically as follows: placing the obtained sample into a supercritical carbon dioxide foaming test device, foaming it at a foaming pressure of 5-25 MPa, and then drying the foam obtained after foaming at 130-180°C for 15-60 minutes, and then heating it to 230-280°C for heat treatment for 15-60 minutes to obtain the final graphene-doped silicone rubber bubble.

[0089] In a preferred embodiment, the process for preparing graphene-doped silicone rubber foam by supercritical foaming comprises the following steps:

[0090] S1. Mixing:

[0091] Methyl vinyl silicone rubber, fumed silica, hydroxy silicone oil, and partially reduced graphene oxide with a reduction degree of 80% were added into an internal mixer at 80° C. in a mass ratio of 100:25:8:5, mixed at a speed of 90 r / min for 30 min, and aged at room temperature for 24 h to obtain a rubber mixture 1;

[0092] S2. Vulcanizing agent mixing:

[0093] The rubber mix and the vulcanizing agent DCP were added into an internal mixer at a mass ratio of 100:2.5, and mixed at room temperature for 10 min at a speed of 60 r / min to obtain a rubber mix 2;

[0094] S3, pre-vulcanization:

[0095] The mixed rubber 2 is placed in a mold with a length×width×thickness of 20 mm×20 mm×2 mm, and placed in a flat vulcanizer at 120° C. for pre-vulcanization. The pre-vulcanization time is 3-25 min to obtain a product to be foamed;

[0096] S4, Supercritical Foaming:

[0097] The product to be foamed is placed in a supercritical foaming device, supercritical dioxide is used as the supercritical fluid, and foaming is carried out under a pressure of 10 MPa for 3 hours. The foam obtained after foaming is then placed in a constant temperature forced air drying oven at 150°C and dried for 30 minutes, and then the temperature is raised to 250°C and heat treated for 0.5 hours to obtain the final graphene-doped silicone rubber foam.

[0098] The present invention also provides a graphene-doped silicone rubber foam, which is prepared by the above process.

[0099] In the present invention, partially reduced graphene oxide (SE2340R, reduction degree 80%) is used, and its surface active groups are helpful for dispersion in silicone rubber. Optimized mixing process: By mixing at 90r / min in an internal mixer at 80°C for 30 minutes, the graphene can be uniformly dispersed in the silicone rubber.

[0100] In the present invention, by controlling the foaming pressure and temperature, a uniform and fine pore structure can be prepared. Specifically, by adjusting the foaming pressure (5MPa to 25MPa), foams with different pore structures can be prepared; higher foaming pressure can prepare finer pores and improve the mechanical properties and thermal conductivity of the foam. The foaming temperature is controlled at about 60°C to ensure that the solubility and diffusion coefficient of supercritical carbon dioxide in silicone rubber are appropriate, thereby preparing a uniform pore structure. By controlling the foaming time and the pressure relief speed, the formation and stability of the pores are ensured. Usually, the foaming time is 3 hours and the pressure relief time is less than 2 seconds.

[0101] In the present invention, the pre-vulcanization conditions are optimized to ensure that the vulcanization reaction is fully carried out. Specifically, an appropriate pre-vulcanization temperature (120°C) is selected to ensure that the vulcanizing agent DCP is evenly distributed and fully reacted in the silicone rubber. The pre-vulcanization time is adjusted (5 minutes to 20 minutes) to ensure that the vulcanization reaction is fully carried out, and a structurally stable compound rubber is prepared. A mold with a length × width × thickness of 20 mm × 20 mm × 2 mm is used to ensure that the compound rubber is evenly heated and formed during the pre-vulcanization process.

[0102] In the present invention, the complete vulcanization and stable performance of the foam can be ensured by a suitable post-treatment process. Specifically, the foamed sample is placed in a constant temperature blast drying oven at 150°C for 30 minutes to ensure that the moisture and residual gas in the foam are completely removed, thereby improving the mechanical properties and thermal conductivity of the foam. The dried sample is heated to 250°C for 0.5 hours to further improve the vulcanization degree of the foam and ensure the structural stability and performance consistency of the foam.

[0103] The present invention can not only improve the performance of silicone rubber foam by optimizing the supercritical foaming process and the doping method of graphene, but also further optimize the comprehensive performance of the foam by using different types of graphene, changing the foaming agent and adjusting the pre-vulcanization conditions.

[0104] In summary, the present invention has been optimized and improved in at least the following aspects:

[0105] Uniform dispersion of graphene: Ensure uniform dispersion of graphene in the silicone rubber matrix by selecting the appropriate graphene type, optimizing the mixing process and adding additives.

[0106] Supercritical carbon dioxide foaming technology: By controlling the foaming pressure, temperature and time, a uniform and fine pore structure is prepared to improve the mechanical properties and thermal conductivity of the foam.

[0107] Pre-vulcanization process: By optimizing the pre-vulcanization temperature and time, the vulcanization reaction is ensured to be fully carried out and a structurally stable compound rubber is prepared.

[0108] Post-treatment process: Through drying and heat treatment, ensure the complete vulcanization and stable performance of the foam.

[0109] The comprehensive application of these key technical points enables the present invention to prepare silicone rubber foam with high strength, good thermal conductivity, excellent cushioning performance, low density, high hardness and environmental friendliness, meeting the needs of various application fields.

[0110] The above is the overall concept of the present invention, and detailed embodiments and comparative examples are provided below on the basis of the overall concept of the present invention to further illustrate the present invention.

[0111] The main raw materials and equipment used in the following examples and comparative examples are from the following sources:

[0112] Methyl vinyl silicone rubber, 110-2 (vinyl mass fraction 0.23%), viscosity average molecular weight about 6.5×10 5 g / mol, Zhejiang Xin'an Chemical Industry Group Co., Ltd.;

[0113] Partially reduced graphene oxide (SE2340R, reduction degree 80%, Changzhou Sixth Element Technology Co., Ltd.);

[0114] Hydroxy silicone oil, GY-209-3, Zhonghao Chenguang Chemical Research Institute Co., Ltd.;

[0115] Dicumyl peroxide (DCP), analytical grade, obtained from Shenyang Xinxi Reagent Factory;

[0116] Carbon dioxide gas (CO2), a product of Sichuan Runtai Special Gas Co., Ltd.

[0117] Supercritical carbon dioxide (SC CO2) foaming test device, Beijing Century Senlang Experimental Instrument Co., Ltd.;

[0118] KCI-50 internal mixer, Nanjing Kärcher Machinery Co., Ltd.;

[0119] BL-6170-B high temperature flat vulcanizing machine (program-controlled type), Dongguan Houjie Baisheng Machinery Equipment Factory;

[0120] DZF-6050 vacuum drying oven, Shanghai Langgan Experimental Equipment Co., Ltd.;

[0121] DHG-9075A electric constant temperature blast drying oven, Henan Xinling Instrument Equipment Co., Ltd.

[0122] The relevant performance test methods or standards involved in the following examples and comparative examples are as follows:

[0123] 1. Apparent density

[0124] Test method: Test in accordance with GB / T 6343-2009 “Determination of apparent density of plastics”.

[0125] 2. Hardness (Shore A)

[0126] Test method: Test in accordance with GB / T 531.1-2008 "Test method for indentation hardness of vulcanized rubber or thermoplastic rubber Part 1: Shore durometer method".

[0127] 3. Tensile strength

[0128] Test method: Test in accordance with GB / T 1040.2-2006 “Determination of tensile properties of plastics Part 2: Test conditions for molded and extruded plastics”.

[0129] 4. Compression set

[0130] Test method: Test in accordance with GB / T 7759-2015 "Determination of compression set of vulcanized rubber or thermoplastic rubber at room temperature, high temperature and low temperature".

[0131] Example 1

[0132] A process for preparing graphene-doped silicone rubber foam by supercritical foaming, the process comprising the following steps:

[0133] S1. Mixing:

[0134] Methyl vinyl silicone rubber, fumed silica, hydroxy silicone oil, and partially reduced graphene oxide were sequentially added into an internal mixer at 80° C. in a mass ratio of 100:25:8:0.5, mixed for 30 minutes at a speed of 90 r / min, and aged at room temperature for 24 hours to achieve structural stability, thereby obtaining a rubber compound 1;

[0135] S2. Vulcanizing agent mixing:

[0136] The rubber compound 1 and the vulcanizing agent DCP were added into an internal mixer at a mass ratio of 100:2.5, and mixed at room temperature for 10 min at a speed of 60 r / min to obtain a rubber compound 2;

[0137] S3, pre-vulcanization:

[0138] The mixed rubber 2 was placed in a mold with a length×width×thickness of 20 mm×20 mm×2 mm, and placed in a flat vulcanizer at 120° C. for pre-vulcanization for 10 minutes to obtain a product to be foamed;

[0139] S4, Supercritical Foaming:

[0140] The product to be foamed is placed in a supercritical foaming device, supercritical dioxide is used as the supercritical fluid, and foaming is carried out under a pressure of 10 MPa for 3 hours. The foam obtained after foaming is then placed in a constant temperature forced air drying oven at 150°C and dried for 30 minutes, and then the temperature is raised to 250°C and heat treated for 0.5 hours to obtain the final graphene-doped silicone rubber foam.

[0141] Test performance:

[0142] The test results are as follows:

[0143] Apparent density (g / cm 3 ): 0.7675;

[0144] Hardness (Shore A): 35;

[0145] Tensile strength (MPa): 3.5;

[0146] Compression set (%): 24.

[0147] Test result analysis description:

[0148] Apparent density: The addition of graphene makes the pore structure more uniform and reduces the density.

[0149] Hardness: The addition of graphene increases the hardness of the foam.

[0150] Tensile strength: The excellent mechanical properties of graphene improve the tensile strength of foam.

[0151] Compression set: Optimization of the cell structure reduces permanent set after compression.

[0152] Compression strength: The optimization of the cell structure improves the compression strength of the foam.

[0153] Embodiment 2-6

[0154] The difference between this group of examples and Example 1 is that the amount of reduced graphene oxide added is changed, and the mass ratio of methyl vinyl silicone rubber, fumed silica, hydroxy silicone oil, and partially reduced graphene oxide with a reduction degree of 80% is 100:25:8:A;

[0155] The specific value of ratio A and the test results of the corresponding products are shown in Table 1 below:

[0156] Table 1

[0157]

[0158] Test result analysis description:

[0159] Apparent density: With the increase of graphene content, the pore structure becomes more uniform and the density increases slightly.

[0160] Hardness: The addition of graphene increases the hardness of the foam.

[0161] Tensile strength: The excellent mechanical properties of graphene improve the tensile strength of foam, but too much graphene added leads to a decrease in material performance.

[0162] Compression set: Optimization of the cell structure reduces permanent set after compression.

[0163] Embodiment 7-11

[0164] The difference between this group of embodiments and embodiment 4 is only that the foaming pressure in step S4 is changed. The specific foaming pressure and the test results of the corresponding products are shown in Table 2 below:

[0165] Table 2

[0166]

[0167] Test result analysis description:

[0168] Apparent density: With the increase of foaming pressure, the pore size gradually decreases and the density increases slightly.

[0169] Hardness: The increase in foaming pressure makes the pore structure more uniform and the hardness increases slightly.

[0170] Tensile strength: The increase in foaming pressure makes the pore structure more uniform and the tensile strength increases.

[0171] Compression set: The increase in foaming pressure makes the cell structure more uniform and the permanent set after compression is reduced.

[0172] Comparative Example

[0173] A process for preparing silicone rubber foam by supercritical foaming, the process comprising the following steps:

[0174] S1. Mixing:

[0175] Methyl vinyl silicone rubber, fumed silica and hydroxy silicone oil were added into an internal mixer at 80° C. in a mass ratio of 100:25:8, mixed for 30 minutes at a speed of 90 r / min, and aged at room temperature for 24 hours to achieve structural stability, thereby obtaining a rubber compound 1;

[0176] S2. Vulcanizing agent mixing:

[0177] The rubber compound 1 and the vulcanizing agent DCP were added into an internal mixer at a mass ratio of 100:2.5, and mixed at room temperature for 10 min at a speed of 60 r / min to obtain a rubber compound 2;

[0178] S3, pre-vulcanization:

[0179] The mixed rubber 2 was placed in a mold with a length×width×thickness of 20 mm×20 mm×2 mm, and placed in a flat vulcanizer at 120° C. for pre-vulcanization for 10 minutes to obtain a product to be foamed;

[0180] S4, Supercritical Foaming:

[0181] The product to be foamed is placed in a supercritical foaming device, supercritical dioxide is used as the supercritical fluid, and foaming is carried out under a pressure of 3MPa for 3 hours. The foam obtained after foaming is then placed in a constant temperature forced air drying oven at 150°C and dried for 30 minutes, and then the temperature is raised to 250°C and heat treated for 0.5 hours to obtain the final graphene-doped silicone rubber foam.

[0182] Test performance:

[0183] The test results are as follows:

[0184] Apparent density (g / cm 3 ): 0.8030;

[0185] Hardness (Shore A): 26;

[0186] Tensile strength (MPa): 1.6;

[0187] Compression set (%): 33.

[0188] Test result analysis description:

[0189] Apparent density: The density of foam without graphene is higher because the pore structure is uneven and the cells are larger.

[0190] Hardness: Foam without graphene has lower hardness.

[0191] Tensile strength: Foam without graphene has lower tensile strength.

[0192] Compression set: The permanent set of the foam without graphene after compression is larger.

[0193] Compression strength: Foam without graphene has lower compression strength.

[0194] By comparison, it can be seen that the embodiments of the present invention significantly improve the comprehensive performance of silicone rubber foam by optimizing the supercritical foaming process and the doping method of graphene, especially in terms of apparent density, hardness, tensile strength, compression permanent deformation and compression strength.

[0195] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to specific details.

Claims

1. A process for preparing graphene-doped silicone rubber foam by supercritical foaming, characterized in that: The following steps are involved: S1. Mixing: Adding methyl vinyl silicone rubber, fumed silica, hydroxy silicone oil and reduced graphene oxide into an internal mixer, mixing under heating, and then aging at room temperature to obtain a rubber mixture 1; S2. Vulcanizing agent mixing: Adding the rubber mix 1 and the vulcanizing agent into an internal mixer, and mixing at room temperature to obtain the rubber mix 2; S3, pre-vulcanization: The mixed rubber 2 is placed in a flat vulcanizer for pre-vulcanization to obtain a product to be foamed; S4, Supercritical Foaming: The product to be foamed is placed in a supercritical foaming device for foaming, and then the foam obtained after foaming is heated and dried, and then heat-treated to obtain the final graphene-doped silicone rubber foam.

2. The process for preparing graphene-doped silicone rubber foam by supercritical foaming according to claim 1, characterized in that: The reduced graphene oxide in step S1 is partially reduced graphene oxide with a reduction degree of 60-90%.

3. The process for preparing graphene-doped silicone rubber foam by supercritical foaming according to claim 2, characterized in that: Step S1 is specifically as follows: Methyl vinyl silicone rubber, fumed silica, hydroxy silicone oil and partially reduced graphene oxide are sequentially added into an internal mixer at 60-100° C. in a mass ratio of 100:25:8:0.5-10, mixed at a speed of 50-200 r / min for 15-60 min, and aged at room temperature for 12-48 h to obtain a rubber mixture 1.

4. The process for preparing graphene-doped silicone rubber foam by supercritical foaming according to claim 1, characterized in that: The vulcanizing agent in step S2 is vulcanizing agent DCP.

5. The process for preparing graphene-doped silicone rubber foam by supercritical foaming according to claim 4, characterized in that: Step S2 is specifically as follows: The rubber mix and the vulcanizing agent DCP were added into an internal mixer at a mass ratio of 100:1-5, and mixed at room temperature for 5-30 minutes at a rotation speed of 30-150 r / min to obtain a rubber mix 2.

6. The process for preparing graphene-doped silicone rubber foam by supercritical foaming according to claim 1, characterized in that: Step S3 is specifically as follows: The rubber compound 2 is placed in a flat vulcanizer at 100-130° C. for pre-vulcanization, with the pre-vulcanization time being 3-25 minutes, to obtain a product to be foamed.

7. The process for preparing graphene-doped silicone rubber foam by supercritical foaming according to claim 1, characterized in that: The supercritical fluid used in the supercritical foaming device in step S4 is any one of supercritical carbon dioxide, supercritical nitrogen, and supercritical butane.

8. The process for preparing graphene-doped silicone rubber foam by supercritical foaming according to claim 7, characterized in that: Step S4 is specifically as follows: The obtained sample is placed in a supercritical carbon dioxide foaming test device and foamed at a foaming pressure of 5-25 MPa. The foam obtained after foaming is then dried at 130-180° C. for 15-60 min, and then heated to 230-280° C. for heat treatment for 15-60 min to obtain the final graphene-doped silicone rubber foam.

9. The process for preparing graphene-doped silicone rubber foam by supercritical foaming according to claim 7, characterized in that: The process includes the following steps: S1. Mixing: Methyl vinyl silicone rubber, fumed silica, hydroxy silicone oil, and partially reduced graphene oxide with a reduction degree of 80% were added into an internal mixer at 80° C. in a mass ratio of 100:25:8:5, mixed at a speed of 90 r / min for 30 min, and aged at room temperature for 24 h to obtain a rubber mixture 1; S2. Vulcanizing agent mixing: The rubber compound 1 and the vulcanizing agent DCP were added into an internal mixer at a mass ratio of 100:2.5, and mixed at room temperature for 10 min at a speed of 60 r / min to obtain a rubber compound 2; S3, pre-vulcanization: The mixed rubber 2 is placed in a mold with a length×width×thickness of 20 mm×20 mm×2 mm, and placed in a flat vulcanizer at 120° C. for pre-vulcanization. The pre-vulcanization time is 3-25 min to obtain a product to be foamed; S4, Supercritical Foaming: The product to be foamed is placed in a supercritical foaming device, supercritical dioxide is used as the supercritical fluid, and foaming is carried out under a pressure of 10 MPa for 3 hours. The foam obtained after foaming is then placed in a constant temperature forced air drying oven at 150°C and dried for 30 minutes, and then the temperature is raised to 250°C and heat treated for 0.5 hours to obtain the final graphene-doped silicone rubber foam.

10. A graphene-doped silicone rubber foam, characterized in that: The method is prepared by the process as described in any one of claims 1 to 9.

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