Self-repairing organic silicon rubber elastomer foam material for vehicle and preparation method of self-repairing organic silicon rubber elastomer foam material

Abstract

The invention belongs to the technical field of self-repairing of microcracks of silicone rubber elastomer foam, and discloses a self-repairing organic silicone rubber elastomer foam material for a vehicle and a preparation method of the self-repairing organic silicone rubber elastomer foam material. The mechanical strength and melt strength of the silicone rubber elastomer are improved by inherent crosslinking, and the self-repairing performance is endowed by dynamic crosslinking. Secondly, soaking and permeating the constructed silicone rubber elastomer system with the inherent crosslinking and dynamic crosslinking dual-network structure by adopting high-pressure fluid until saturation, instantaneously releasing pressure and foaming, enabling the silicone rubber elastomer and the supercritical gas homogeneous system to enter a thermodynamic unstable state, and determining the temperature of the sample under the action of the gas concentration difference inside and outside the sample. The induced gas forms a bubble core in the silicone rubber elastomer, and bubbles grow to form a porous structure. According to the invention, the self-repairing of the foam microcracks of the organic silicon rubber elastomer is realized under the condition of keeping the stability of the foam structure.

Description

Technical Field

[0001] The invention belongs to the technical field of self-repairing microcracks in silicone rubber elastomer foam, and in particular relates to a self-repairing organic silicone rubber elastomer foam material for a vehicle and a preparation method thereof. Background Art

[0002] Silicone rubber foam materials have the excellent properties of both silicone rubber and foam materials. They have the high elasticity of silicone rubber and the properties of foam such as sound absorption, noise reduction, shock absorption, and heat insulation. They are widely used in thermal insulation foam pipes for automotive air conditioners, shock-absorbing gaskets, and foamed silicone sealing gaskets for new energy vehicle batteries. The supercritical fluid foaming method currently used is a green and environmentally friendly foaming method that can effectively control the pore structure. However, it is inevitable that silicone rubber foam materials will produce microcracks during use. If the silicone rubber elastomer foam material can be given self-healing properties, the microcracks caused by the damage of the silicone rubber elastomer foam material can be repaired while ensuring the stability of the pore structure, which can effectively improve the safety and durability of automotive silicone rubber elastomer foam materials.

[0003] At present, the self-healing mechanism of organic silicone rubber elastomer materials can be mainly divided into two categories: external aid type and intrinsic type. External aid type self-healing requires additional addition of repair agents, which is inefficient and cannot be repaired multiple times. Intrinsic self-healing uses the dissociation and association of dynamic chemical bonds on the molecular chain to achieve repair performance, which is efficient and can be repaired multiple times. Under specified conditions, the three-dimensional network structure of dynamic chemical bonds formed by intrinsic organic silicone rubber elastomers is activated, and dynamic chemical bonds can be quickly broken and reorganized to achieve micro-crack repair.

[0004] However, the strong migration ability of the molecular chains of intrinsic silicone rubber elastomers will reduce the stability of the pore structure, and it is still facing many challenges. On the one hand, the migration ability of the molecular chains of intrinsic silicone rubber elastomers is enhanced during the breaking and reorganization of dynamic chemical bonds, which will cause the instability of the pore structure, collapse and merge the pore structure, and disappear the pore structure; on the other hand, the microcrack repair process is also the process of heat shrinkage of the pore wall. The pore wall is an oriented structure formed by unidirectional foaming. When heated, the oriented structure of the pore wall will be deoriented, resulting in shrinkage, which significantly affects the self-repair performance of microcracks in silicone rubber elastomer foam materials.

[0005] Therefore, it is challenging to achieve self-repair of microcracks in silicone rubber elastomer foam, and there is currently no method to solve the problem of self-repair of microcracks in silicone rubber elastomer foam. Summary of the invention

[0006] In view of the problems existing in the prior art, the present invention provides a self-repairing organic silicon rubber elastomer foam material for a vehicle and a preparation method thereof.

[0007] The present invention is achieved by a method for preparing a self-repairing organic silicone rubber elastomer foam material for a vehicle, comprising the following steps:

[0008] S1, synthetic silicone rubber elastomer:

[0009] S11, adding polydimethylsiloxane and a chain extender in molar ratio into a reaction container in sequence, and reacting at room temperature for 6-12 hours;

[0010] S12, heating to 50-70°C, introducing a dynamic cross-linking agent and continuing the reaction for 3-6 hours;

[0011] S13, cooling to 30-50°C, introducing an intrinsic cross-linking agent and continuing the reaction for 3-6 hours;

[0012] S14, pouring the reaction product directly into a mold, vacuum degassing, and after the solvent is completely volatilized, obtaining a silicone rubber elastomer having a dual cross-linked network structure of inherent cross-linking and dynamic cross-linking;

[0013] S2, preparation of self-healing silicone rubber elastomer foam:

[0014] S21, preparing the prepared silicone rubber elastomer into a molded body for foaming, placing the body on a hot plate of a high-pressure reactor; heating the body to 50-80° C., and then introducing a low-pressure foaming gas into the high-pressure reactor;

[0015] S22, after the temperature in the kettle is stabilized, introduce foaming gas to 8-16MPa;

[0016] S23, the pressure is rapidly released to atmospheric pressure within 1s to 3s, so that the homogeneous system of silicone rubber elastomer and supercritical gas enters a thermodynamically unstable state. Under the action of the gas concentration difference inside and outside the sample, the gas is induced to form bubble nuclei in the silicone rubber elastomer, and the bubbles grow to form a porous structure; thus, a silicone rubber elastomer foam with a uniform and stable pore structure is obtained.

[0017] Further, the polydimethylsiloxane in step S11 includes any one of amino-terminated polydimethylsiloxane and hydroxy-terminated polydimethylsiloxane, and the number average molecular weight is between 1000 and 10000. The chain extender includes any one of polyisocyanates such as naphthalene diisocyanate (NDI), isophorone isocyanate (IPDI), p-phenylene diisocyanate (PPDI), and hexamethylene diisocyanate (HDI).

[0018] Furthermore, when hydroxyl-terminated polydimethylsiloxane is used, a catalyst should be added. The catalyst is used to catalyze the exchange reaction. The catalyst includes any one of an organic divalent zinc salt, an organic divalent tin salt and a tertiary amine.

[0019] Furthermore, the dynamic crosslinking agent in step S12 is any one of disulfides such as 4,4'-dithiodiphenylamine (APDS), 2,2'-diaminodiphenyl disulfide (DAPDS), 3,3'-dihydroxydiphenyl disulfide, and bis(4-hydroxyphenyl) disulfide (MSDS).

[0020] Furthermore, the inherent cross-linking agent in step S13 is any one of cross-linking agents such as glycerol and tris(2-aminoethyl)amine.

[0021] Furthermore, in step S14, the reaction solvent is any one of acetone, ethanol, toluene and tetrahydrofuran; and the foaming gas is any one of carbon dioxide, nitrogen and an inert gas.

[0022] Furthermore, in step S21, low-pressure foaming gas is introduced into the high-pressure reactor, and the exhaust valve is opened to exhaust the air in the reactor, which is expected to take 1-3 minutes.

[0023] Furthermore, in step S22, the supercritical condition of the gas is maintained for 2 to 5 hours, so that the gas can completely diffuse and dissolve in the silicone rubber elastomer until saturation, forming a homogeneous system of the silicone rubber elastomer and the gas.

[0024] Another object of the present invention is to provide a self-repairing organic silicon rubber elastomer foam material for vehicles.

[0025] In combination with the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solutions to be protected by the present invention are as follows:

[0026] First, in the preparation of the automotive silicone rubber elastomer foam material, the present invention innovatively proposes to construct a silicone rubber elastomer system with a dual network structure of inherent crosslinking and dynamic crosslinking, replacing the original dynamic crosslinking silicone rubber elastomer system. By adjusting the degree of inherent crosslinking and dynamic crosslinking, the inherent crosslinking improves the mechanical strength and melt strength of the silicone rubber elastomer, and the dynamic crosslinking gives it self-healing properties. Secondly, a high-pressure fluid is used to soak and penetrate the constructed silicone rubber elastomer system with a dual network structure of inherent crosslinking and dynamic crosslinking until saturation and instantaneous pressure relief and foaming, so that the silicone rubber elastomer and supercritical gas homogeneous system enter a thermodynamically unstable state. Under the action of the gas concentration difference inside and outside the sample, the gas is induced to form bubble nuclei in the silicone rubber elastomer, and the bubbles grow to form a porous structure. On the one hand, the inherent crosslinking improves the melt strength, promotes the uniformity and stability of the pore structure, and is conducive to foaming; on the other hand, the molecular chains of the silicone rubber elastomer foam are restricted by the inherent crosslinking molecular chains during the heating process, which can effectively inhibit the deorientation of the pore wall of the foam during the heating process and effectively control the shrinkage of the pore wall. It is precisely because of the coordinated effects of the above aspects that the silicone rubber elastomer foam prepared by foaming has a stable pore structure.

[0027] The present invention explores the construction conditions and foaming conditions of a silicone rubber elastomer system with a dual network structure of inherent crosslinking and dynamic crosslinking, realizes the self-repair of microcracks in silicone rubber elastomer foam while maintaining the stability of the pore structure, and proposes a new idea for the construction of self-healing silicone rubber elastomer foam materials. This breaks through the technical bottleneck of self-repair of silicone rubber elastomer foam materials, solves the problem that silicone rubber elastomer foam materials in the prior art are difficult to achieve stable pore structure and self-repair of microcracks, and achieves important technical innovation in extending the service life and safety of automotive silicone rubber elastomer foam materials.

[0028] Second, existing automotive elastomer foam materials have significant deficiencies in durability, self-healing ability, and uniformity of foaming structure. Traditional methods for preparing silicone rubber elastomers often rely solely on a single cross-linking mechanism, which makes it difficult for the material to achieve effective self-repair after damage, reducing its service life and safety in automotive applications. In addition, traditional foaming processes lack precise control methods for bubble nucleus formation and pore structure control, resulting in uneven pore distribution, which affects the mechanical properties and sound insulation effect of the material. Therefore, how to prepare silicone rubber elastomer foam materials with high self-healing ability and uniform and stable pore structure by optimizing the cross-linking system and foaming process has become a technical problem that needs to be solved urgently.

[0029] The present invention effectively solves the above technical problems by introducing a dual cross-linking system (inherent cross-linking and dynamic cross-linking) and optimizing the foaming process parameters. In step S1, polydimethylsiloxane is reacted with a variety of chain extenders in a specific molar ratio to ensure the stability of the basic network structure of the elastomer. Further, a dynamic cross-linking agent and an inherent cross-linking agent are introduced in steps S12 and S13 to form a dual cross-linked network structure with a self-repairing function, which greatly improves the self-healing ability of the material after damage. At the same time, through the rapid pressure relief solid-state foaming process of the high-pressure reactor in step S2, the injection and release rates of the foaming gas are accurately controlled to achieve uniform formation of bubble nuclei and stability of the pore structure. These parameter optimizations not only improve the self-repairing properties of the material, but also significantly improve the uniformity of the pore structure, and enhance the overall mechanical properties and sound insulation effect of the elastomer.

[0030] The preparation method of the present invention has achieved significant technical progress. The obtained automotive self-repairing silicone rubber elastomer foam material has efficient self-repairing ability and uniform and stable pore structure, which significantly improves the application performance of the material in automotive shock absorption, sound insulation and safety protection. Through the optimized double cross-linking system and precise foaming process, the material can quickly self-heal after mechanical damage, extending its service life and reducing maintenance costs. At the same time, the uniform pore structure gives the material excellent mechanical properties and sound insulation effects, meeting the needs of modern automobiles for high-performance elastic materials. This technological advancement not only fills the key gaps in the prior art, but also provides solid technical support for the widespread application of automotive elastomer foam materials, and has broad market prospects and significant commercial value. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a flow chart of a method for preparing a self-repairing organic silicone rubber elastomer foam material for a vehicle provided by an embodiment of the present invention;

[0032] Figure 2 is a flow chart of a synthetic silicone rubber elastomer provided by an embodiment of the present invention;

[0033] Figure 3 is a flow chart of preparing a self-repairing silicone rubber elastomer foam provided by an embodiment of the present invention;

[0034] Figure 4 Schematic diagram of the preparation principle of the silicone rubber elastomer provided by an embodiment of the present invention;

[0035] Figure 5 is a schematic diagram of a foaming solution provided in an embodiment of the present invention;

[0036] Figure 6 : are SEM images of the PISTF cell structures provided in the embodiments of the present invention; (a) Comparative Example 3; (b) Example 2; (c) Comparative Example 4;

[0037] Figure 7 The SEM images of the cell structure of the PISTF provided in the embodiments of the present invention after being placed for 96 hours; (a) Comparative Example 3; (b) Example 2; (c) Comparative Example 4;

[0038] Figure 8 These are SEM images of the PISTF provided in an embodiment of the present invention before and after crack healing after being placed for 96 hours; (a) (b) Example 2; (c) (d) Comparative Example 4. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0040] like Figure 1 As shown, an embodiment of the present invention provides a method for preparing a self-repairing organic silicone rubber elastomer foam material for a vehicle, comprising the following steps:

[0041] S1, synthetic silicone rubber elastomer:

[0042] S11, adding polydimethylsiloxane and a chain extender in molar ratio into a reaction container in sequence, and reacting at room temperature for 6-12 hours;

[0043] S12, heating to 50-70°C, introducing a dynamic cross-linking agent and continuing the reaction for 3-6 hours;

[0044] S13, cooling to 30-50°C, introducing an intrinsic cross-linking agent and continuing the reaction for 3-6 hours;

[0045] S14, pouring the reaction product directly into a mold, vacuum degassing, and after the solvent is completely volatilized, obtaining a silicone rubber elastomer having a dual cross-linked network structure of inherent cross-linking and dynamic cross-linking;

[0046] S2, preparation of self-healing silicone rubber elastomer foam:

[0047] S21, preparing the prepared silicone rubber elastomer into a molded body for foaming, placing the body on a hot plate of a high-pressure reactor; heating the body to 50-80° C., and then introducing a low-pressure foaming gas into the high-pressure reactor;

[0048] S22, after the temperature in the kettle is stabilized, introduce foaming gas to 8-16MPa;

[0049] S23, the pressure is rapidly released to atmospheric pressure within 1s to 3s, so that the homogeneous system of silicone rubber elastomer and supercritical gas enters a thermodynamically unstable state. Under the action of the gas concentration difference inside and outside the sample, the gas is induced to form bubble nuclei in the silicone rubber elastomer, and the bubbles grow to form a porous structure; thus, a silicone rubber elastomer foam with a uniform and stable pore structure is obtained.

[0050] The preparation of silicone rubber elastomers is a key step in constructing a double cross-linked network through chemical reactions. First, polydimethylsiloxane and chain extenders are added to the reaction vessel in a predetermined molar ratio, and the chain growth reaction is carried out at room temperature for 6-12 hours to enhance the length and flexibility of the molecular chain. Subsequently, the system is heated to 50-70°C, and a dynamic cross-linker is added to initiate a dynamic cross-linking reaction for 3-6 hours. The dynamic cross-linker provides reversible chemical bonds, giving the elastomer self-healing properties. Next, the reaction temperature is lowered to 30-50°C, and an inherent cross-linker is added for an inherent cross-linking reaction to further stabilize the network structure. This process enables silicone rubber elastomers to have both high elasticity and self-healing functions by constructing a dual network in which dynamic and inherent cross-linking coexist.

[0051] After the cross-linking reaction is completed, the obtained silicone rubber elastomer is directly poured into the mold and vacuum degassing is performed to remove the residual bubbles in the system to ensure the structural uniformity and stability of the elastomer. After the degassing is completed, the elastomer is fully cured and a stable double-network cross-linking structure is formed by the natural evaporation of the solvent. The prepared silicone rubber elastomer has high elasticity and fatigue resistance, and at the same time lays a physical and chemical foundation for the subsequent foaming process.

[0052] The silicone rubber elastomer is prepared into a molded body for foaming, placed on a hot stage of a high-pressure reactor, and heated to 50-80°C to provide sufficient thermal diffusion rate for gas diffusion. Subsequently, a low-pressure foaming gas (such as carbon dioxide or nitrogen) is introduced into the reactor for 1-3 minutes to remove the air in the reactor. Subsequently, the pressure of the foaming gas is rapidly increased to 8-16MPa and maintained for 2-5 hours, so that the gas can be evenly diffused into the elastomer to form a gas-solid homogeneous system, avoiding bubble defects caused by uneven gas distribution. Immediately afterwards, the pressure is quickly released to atmospheric pressure within 1-3 seconds, causing the system to enter a thermodynamically unstable state. At this time, due to the concentration gradient of the gas inside and outside the silicone rubber elastomer, the induced gas is rapidly precipitated and bubble nuclei are formed. These bubble nuclei expand stably with the support of the silicone rubber elastomer, and finally form a uniform porous structure inside the elastomer. The obtained foam has excellent mechanical properties and cell stability, and maintains the self-healing ability of the silicone rubber elastomer, which is suitable for the field of automotive elastomer foam materials.

[0053] The first step in preparing the self-healing silicone rubber elastomer foam material for automobiles is to synthesize the silicone rubber elastomer (step S1). In step S11, polydimethylsiloxane (PDMS) and a chain extender are sequentially added to a reaction vessel in a predetermined molar ratio and reacted at room temperature for 6 to 12 hours. As a base polymer, polydimethylsiloxane provides excellent elasticity and temperature resistance, while the chain extender enhances the network structure of the elastomer through a chemical reaction with PDMS, thereby improving the mechanical strength and elasticity of the material. In step S12, the reaction temperature is increased to 50-70°C, a dynamic crosslinker is introduced, and the reaction is continued for 3 to 6 hours. Dynamic crosslinkers (such as disulfide compounds) promote crosslinking reactions at higher temperatures, form reversible chemical bonds, and give the material self-healing capabilities. Then, in step S13, the temperature is reduced to 30-50°C, an intrinsic crosslinker is introduced, and the reaction is continued for 3 to 6 hours. Intrinsic crosslinkers (such as propylene glycol or tris(2-aminoethyl)amine) further enhance the network structure of the silicone rubber elastomer and ensure the stability and durability of the material. Finally, in step S14, the reaction product is poured into a mold and subjected to vacuum degassing treatment. After the solvent is completely volatilized, a silicone rubber elastomer having a dual cross-linked network structure of inherent cross-linking and dynamic cross-linking is obtained. This dual cross-linked network not only improves the mechanical properties of the material, but also gives it excellent self-healing ability.

[0054] After the silicone rubber elastomer is synthesized, the second step (step S2) of preparing the self-healing silicone rubber elastomer foam is entered. In step S21, the synthesized silicone rubber elastomer is prepared into a molded body for foaming and placed on a hot stage in a high-pressure reactor. Subsequently, the temperature is raised to 50-80°C, and a low-pressure foaming gas (such as carbon dioxide, nitrogen or other inert gases) is passed into the high-pressure reactor. In step S22, when the temperature in the reactor is stable, the foaming gas is continuously introduced to a pressure range of 8-16MPa. Under high pressure, the gas is fully dissolved in the silicone rubber elastomer to form a homogeneous solution. Then, in step S23, the pressure of the reactor is quickly released to atmospheric pressure within 1 to 3 seconds, so that the homogeneous system of the silicone rubber elastomer and the supercritical gas enters a thermodynamically unstable state. In this process, the gas concentration difference drives the gas to form bubble nuclei in the silicone rubber elastomer, which gradually develops into a porous structure. This rapid foaming process ensures the uniformity and stability of the pore structure, thereby producing silicone rubber elastomer foam materials with excellent mechanical properties and self-healing capabilities.

[0055] The present invention forms a silicone rubber elastomer network structure with high toughness and self-healing ability through the dual crosslinking system (inherent crosslinking and dynamic crosslinking) in step S1. The permanent crosslinking network formed by the inherent crosslinking agent provides the basic elasticity and structural stability of the material, while the reversible crosslinking network formed by the dynamic crosslinking agent gives the material self-healing ability. When the material is mechanically damaged, the reversible bonds in the dynamic crosslinking network break and reform, thereby achieving self-healing of the cracks. This dual crosslinking structure not only improves the durability and service life of the material, but also enables the material to maintain good performance after multiple damages, greatly improving its application value and reliability in the automotive field.

[0056] In step S2, the uniform formation of bubble nuclei and the stability of the pore structure are successfully achieved through the rapid pressure relief process in the autoclave. Temperature and pressure control during the foaming process is crucial to ensure the full dissolution and uniform distribution of the gas in the silicone rubber elastomer. Rapid pressure relief allows the dissolved gas to precipitate quickly, forming tiny and evenly distributed bubble nuclei, which then develop into a uniform pore structure. By adjusting the type of foaming gas, pressure range and pressure relief speed, the size and distribution of the bubbles can be precisely controlled, thereby optimizing the mechanical properties and sound insulation effect of the material. The uniform pore structure not only enhances the elasticity and compression resistance of the material, but also improves its sound insulation and shock absorption effects, meeting the needs of automotive elastomer foam materials in high-performance applications.

[0057] The present invention achieves significant improvement in material performance by precisely controlling the reaction conditions and component ratios of each step during the synthesis and foaming process. In step S11, different types of polydimethylsiloxane and chain extenders are selected to optimize the basic properties of the elastomer; the introduction of dynamic crosslinkers and inherent crosslinkers in steps S12 and S13 optimizes the self-healing ability and mechanical strength of the material; and the optimization of the foaming process parameters in steps S21 to S23 ensures the uniformity and stability of the pore structure. These parameter optimizations not only improve the overall performance of the material, but also give it the potential for wide application in the automotive field, such as automotive shock absorption, sound insulation, and safety protection, significantly improving the market competitiveness and application value of the material.

[0058] Through the preparation method of the present invention, the obtained automotive self-healing silicone rubber elastomer foam material has efficient self-healing ability and excellent pore structure, which greatly improves its application performance in the automotive industry. The self-healing ability of the material prolongs its service life and reduces maintenance costs; the uniform pore structure gives the material excellent mechanical properties and sound insulation effects, meeting the needs of modern automobiles for high-performance elastic foam materials. In addition, the material also has broad application prospects in other fields such as building sound insulation, shockproof equipment, etc. Through the optimized double cross-linking system and precise foaming process, the present invention not only fills the key gaps in the prior art, but also provides solid technical support for the widespread application of automotive elastomer foam materials, and has significant commercial value and broad market prospects.

[0059] The method for preparing the automotive self-repairing silicone rubber elastomer foam material of the present invention successfully solves the shortcomings of traditional materials in terms of durability, self-repairing ability and uniformity of pore structure by optimizing the cross-linking system and foaming process, and achieves a significant improvement in material performance. This technological advancement not only improves the application performance of the material in automotive shock absorption, sound insulation and safety protection, but also has broad commercial value and market prospects, providing strong support for the innovative development of automotive elastomer foam materials.

[0060] Further, the polydimethylsiloxane in step S11 includes any one of amino-terminated polydimethylsiloxane and hydroxy-terminated polydimethylsiloxane, and the number average molecular weight is between 1000 and 10000. The chain extender includes any one of polyisocyanates such as naphthalene diisocyanate (NDI), isophorone isocyanate (IPDI), p-phenylene diisocyanate (PPDI), and hexamethylene diisocyanate (HDI).

[0061] Furthermore, when hydroxyl-terminated polydimethylsiloxane is used, a catalyst should be added. The catalyst is used to catalyze the exchange reaction. The catalyst includes any one of an organic divalent zinc salt, an organic divalent tin salt and a tertiary amine.

[0062] Furthermore, the dynamic crosslinking agent in step S12 is any one of disulfides such as 4,4'-dithiodiphenylamine (APDS), 2,2'-diaminodiphenyl disulfide (DAPDS), 3,3'-dihydroxydiphenyl disulfide, and bis(4-hydroxyphenyl) disulfide (MSDS).

[0063] Furthermore, the inherent cross-linking agent in step S13 is any one of cross-linking agents such as glycerol and tris(2-aminoethyl)amine.

[0064] Furthermore, in step S14, the reaction solvent is any one of acetone, ethanol, toluene and tetrahydrofuran; and the foaming gas is any one of carbon dioxide, nitrogen and an inert gas.

[0065] Furthermore, in step S21, low-pressure foaming gas is introduced into the high-pressure reactor, and the exhaust valve is opened to exhaust the air in the reactor, which is expected to take 1-3 minutes.

[0066] Furthermore, in step S22, the supercritical condition of the gas is maintained for 2 to 5 hours, so that the gas can completely diffuse and dissolve in the silicone rubber elastomer until saturation, forming a homogeneous system of the silicone rubber elastomer and the gas.

[0067] Example 1

[0068] A method for preparing a silicone rubber elastomer having a dual network structure of inherent crosslinking and dynamic crosslinking, the preparation steps being:

[0069] (1) Under nitrogen protection, add 3.2 g of isophorone isocyanate (IPDI) to 34 g of polydimethylsiloxane (PDMS, Mn: 3000), and stir with a rotor in an oil bath for 12 h;

[0070] (2) Under nitrogen protection, the temperature of the oil bath in step (1) was raised to 60° C., 0.37 g of 4,4'-diphenylamine disulfide (APDS) was added, and the mixture was stirred with a rotor for 6 h;

[0071] (3) Under nitrogen protection, the temperature of the oil bath in step (2) was lowered to 45°C, 0.10 g of tris(2-aminoethyl)amine (TAEA) was added as a cross-linking agent, and the reaction was stirred for 6 h.

[0072] (4) The product obtained in step (3) is directly poured into a square polytetrafluoroethylene mold, and allowed to volatilize in a fume hood for 12 hours, and then further volatilized in an ordinary blast oven at 120° C. for 2 hours to obtain an elastomer, which is the silicone rubber elastomer having a dual network structure of intrinsic crosslinking and dynamic crosslinking of the present invention, denoted as PIST 0.050 .

[0073] Silicone rubber elastomer preparation process diagram Figure 4 shown.

[0074] Comparative Example 1

[0075] The operation of this comparative example is basically the same as that of Example 1, except that step (3) is removed, the amount of APDS added in step (2) is replaced from 0.37 g to 0.60 g, and the prepared silicone rubber elastomer is recorded as PIST0.

[0076] Comparative Example 2

[0077] The operation of this comparative example is basically the same as that of Example 1, except that step (2) is removed and the amount of TAEA added in step (3) is replaced from 0.10 g to 0.23 g. The prepared silicone rubber elastomer is denoted as PIST 0.133 .

[0078] Example 2

[0079] This example uses the PIST prepared in Example 1 0.050 Based on the present invention, a method for preparing a silicone rubber elastomer foam having a dual network structure of inherent crosslinking and dynamic crosslinking is provided, and the preparation steps are as follows:

[0080] (1) The obtained silicone rubber elastomer is prepared into a foamed blank, and a flat vulcanizer is used to form a PIST 0.050 The hot pressing was performed to obtain a sheet-shaped green body with a thickness of 2 mm. The hot pressing temperature and pressure were 120° C. and 10 MPa, respectively.

[0081] (2) Place the sheet-shaped body on the hot plate of the autoclave, control the temperature of the autoclave to 60°C, then introduce low-pressure foaming gas into the autoclave, open the exhaust valve, and exhaust the air in the autoclave for an estimated 3 minutes. After the temperature in the autoclave stabilizes, introduce foaming gas to 12MPa. Maintain the supercritical condition of the gas for 4 hours; quickly release the pressure to atmospheric pressure within 1 second to obtain a silicone rubber elastomer foam with a uniform pore structure, stable inherent cross-linking and dynamic cross-linking dual network structure, denoted as PISTF 0.050 .

[0082] Foaming scheme diagram Figure 5 shown.

[0083] The PISTF prepared in this example 0.050 The cross section was analyzed by scanning electron microscopy. Figure 6 After being placed at room temperature for 96 hours, the cross section was analyzed by scanning electron microscopy. Figure 7 As shown. Then the cut surface was scratched with a blade, the cell structure was still stable, the cell wall was destroyed, and microcracks were generated. Then it was cured in an oven at 80℃ for 4 minutes. Then it was observed by scanning electron microscopy, and it was found that the microcracks in the cut surface of the healed sample disappeared, as shown. Figure 8 As shown in the figure. 0.050 It has the ability to self-repair microcracks and has a stable pore structure.

[0084] Comparative Example 3

[0085] This comparative example is based on the PIST0 prepared in comparative example 1 to prepare a silicone rubber elastomer foam and observe its self-healing performance:

[0086] (1) The obtained silicone rubber elastomer is prepared into a foamed blank, and PIST0 is hot-pressed using a flat vulcanizer to obtain a sheet-shaped blank with a thickness of 2 mm. The hot-pressing temperature and pressure are 120° C. and 10 MPa, respectively.

[0087] (2) Place the sheet-shaped green body on the hot plate of the autoclave, control the temperature of the autoclave to 60°C, then introduce low-pressure foaming gas into the autoclave, open the exhaust valve, and exhaust the air in the autoclave for an estimated 3 minutes. After the temperature in the autoclave stabilizes, introduce foaming gas to 12MPa. Maintain the supercritical condition of the gas for 4 hours; quickly release the pressure to atmospheric pressure within 1 second to obtain a silicone rubber elastomer foam with uniform pore structure, stable inherent cross-linking and dynamic cross-linking dual network structure, recorded as PISTF0.

[0088] The cross section of PISTF0 prepared in this embodiment was analyzed by scanning electron microscope. Figure 6 After being placed at room temperature for 96 hours, the cross section was analyzed by scanning electron microscopy. Figure 7 It was observed that the pore structure collapsed and pores appeared, and the pore structure was unstable.

[0089] Comparative Example 4

[0090] This comparative example is based on the PIST prepared in Comparative Example 2. 0.133 Based on the preparation method of silicone rubber elastomer foam and observe its self-healing performance:

[0091] (1) The obtained silicone rubber elastomer is prepared into a foamed blank, and a flat vulcanizer is used to form a PIST 0.133 The hot pressing was performed to obtain a sheet-shaped green body with a thickness of 2 mm. The hot pressing temperature and pressure were 120° C. and 10 MPa, respectively.

[0092] (2) Place the sheet-shaped body on the hot plate of the autoclave, control the temperature of the autoclave to 60°C, then introduce low-pressure foaming gas into the autoclave, open the exhaust valve, and exhaust the air in the autoclave for an estimated 3 minutes. After the temperature in the autoclave stabilizes, introduce foaming gas to 12MPa. Maintain the supercritical condition of the gas for 4 hours; quickly release the pressure to atmospheric pressure within 1 second to obtain a silicone rubber elastomer foam with a uniform pore structure, stable inherent cross-linking and dynamic cross-linking dual network structure, denoted as PISTF 0.133 .

[0093] The PISTF prepared in this example 0.133 The cross section was analyzed by scanning electron microscopy. Figure 6 After being placed at room temperature for 96 hours, the cross section was analyzed by scanning electron microscopy. Figure 7As shown. Then the cut surface was scratched with a blade, the cell structure was still stable, the cell wall was destroyed, and microcracks were generated. Then it was cured in an oven at 80℃ for 4 minutes. Then it was observed by scanning electron microscopy, and it was found that the microcracks in the cut surface of the healed sample did not completely disappear, as shown. Figure 8 As shown in the figure. 0.133 It does not have the ability to self-repair microcracks, but the pore structure remains stable.

[0094] The various parameters of the PISTF cell structure after foaming are shown in Table 1

[0095] Table 1

[0096]

[0097] Relevant evidence of the technical effects achieved by the embodiments of the present invention.

[0098] Analytical test methods:

[0099] Scanning electron microscopy analysis

[0100] The cross section of silicone rubber foam was analyzed by field emission scanning electron microscopy (SEM) to explore the cell size and cell crack repair. The analysis instrument was a SU8010 scanning electron microscope from HITACHI, Japan. Figure 6 The SEM image of the cross section of the silicone rubber foam sample. The average pore size and pore size distribution were calculated from the SEM photo using Image J software. The pore density was calculated according to the method proposed by Kumar et al., where n (>100) is the number of pores in the SEM micrograph and A is the area of ​​the SEM micrograph (in cm 2 ), ρ p is the matrix density (in g / cm 3 ), ρ f is the foam density (in g / cm 3 ), the basic idea is to convert the two-dimensional area density into three-dimensional volume density. The pore density per unit volume is:

[0101]

[0102] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a self-repairing silicone rubber elastomer foam material for a vehicle, characterized in that: The following steps are involved: S1, synthetic silicone rubber elastomer: S11, adding polydimethylsiloxane and a chain extender in molar ratio into a reaction container in sequence, and reacting at room temperature for 6-12 hours; S12, heating to 50-70°C, introducing a dynamic cross-linking agent and continuing the reaction for 3-6 hours; S13, cooling to 30-50°C, introducing an intrinsic cross-linking agent and continuing the reaction for 3-6 hours; S14, pouring the reaction product directly into a mold, vacuum degassing, and after the solvent is completely volatilized, obtaining a silicone rubber elastomer having a dual cross-linked network structure of inherent cross-linking and dynamic cross-linking; S2, preparation of self-healing silicone rubber elastomer foam: S21, preparing the prepared silicone rubber elastomer into a molded body for foaming, placing the body on a hot plate of a high-pressure reactor; heating the body to 50-80° C., and then introducing a low-pressure foaming gas into the high-pressure reactor; S22, after the temperature in the kettle is stabilized, introduce foaming gas to 8-16MPa; S23, the pressure is rapidly released to atmospheric pressure within 1s to 3s, so that the homogeneous system of silicone rubber elastomer and supercritical gas enters a thermodynamically unstable state. Under the action of the gas concentration difference inside and outside the sample, the gas is induced to form bubble nuclei in the silicone rubber elastomer, and the bubbles grow to form a porous structure; thus, a silicone rubber elastomer foam with a uniform and stable pore structure is obtained.

2. The method for preparing the vehicle self-repairing organic silicone rubber elastomer foam material according to claim 1, characterized in that: The polydimethylsiloxane in step S11 includes any one of amino-terminated polydimethylsiloxane and hydroxy-terminated polydimethylsiloxane, and the number average molecular weight is between 1000 and 10000. The chain extender includes any one of polyisocyanates such as naphthalene diisocyanate (NDI), isophorone isocyanate (IPDI), p-phenylene diisocyanate (PPDI), and hexamethylene diisocyanate (HDI).

3. The method for preparing the vehicle self-repairing silicone rubber elastomer foam material according to claim 1, characterized in that: When hydroxyl-terminated polydimethylsiloxane is used, a catalyst should also be added. The catalyst is used to catalyze the exchange reaction. The catalyst includes any one of an organic divalent zinc salt, an organic divalent tin salt and a tertiary amine.

4. The method for preparing the vehicle self-repairing silicone rubber elastomer foam material according to claim 1, characterized in that: The dynamic cross-linking agent in step S12 is any one of disulfides such as 4,4'-diphenylamine disulfide (APDS), 2,2'-diaminodiphenyl disulfide (DAPDS), 3,3'-dihydroxydiphenyl disulfide, and bis(4-hydroxyphenyl) disulfide (MSDS).

5. The method for preparing the vehicle self-repairing silicone rubber elastomer foam material according to claim 1, characterized in that: The intrinsic cross-linking agent in step S13 is any one of cross-linking agents such as glycerol and tris(2-aminoethyl)amine.

6. The method for preparing the vehicle self-repairing silicone rubber elastomer foam material according to claim 1, characterized in that: In step S14, the reaction solvent is any one of acetone, ethanol, toluene and tetrahydrofuran; the foaming gas is any one of carbon dioxide, nitrogen and inert gas.

7. The method for preparing the vehicle self-repairing organic silicone rubber elastomer foam material according to claim 1, characterized in that: In step S21, low-pressure foaming gas is introduced into the high-pressure reactor, and the exhaust valve is opened to exhaust the air in the reactor, which is expected to take 1-3 minutes.

8. The method for preparing the vehicle self-repairing silicone rubber elastomer foam material according to claim 1, characterized in that: In step S22, the supercritical condition of the gas is maintained for 2 to 5 hours, so that the gas can be completely diffused and dissolved in the silicone rubber elastomer until saturation, forming a homogeneous system of the silicone rubber elastomer and the gas.

9. A vehicle self-repairing organosilicon rubber elastomer foam material obtained by the method for preparing a vehicle self-repairing organosilicon rubber elastomer foam material as claimed in any one of claims 1 to 8.

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