High and low temperature resistant rubber and preparation method thereof

Abstract

The invention discloses high and low temperature resistant rubber and a preparation method thereof, and relates to the technical field of rubber materials. Polyurethane and ceramic aerogel are combined to form a semi-interpenetrating network to prepare the hybrid filler, amino groups on the surface of the aerogel react with isocyanate groups of the polyurethane to generate covalent bonds, polyether / polyester soft segments of the polyurethane serve as flexible chain segments, the movement ability of molecular chain segments is still kept at extremely low temperature, and the hybrid filler is prepared. Meanwhile, nanopores of the aerogel obstruct heat conduction of gas. Carrying out nucleophilic addition on phosphoric acid and epoxy groups of the hollow glass beads, and adding a hybrid filler into silicone rubber for modification; the phosphate group and a chain in the silicone rubber form a hydrogen bond; hydrogen bonds interact to form a polyurethane / aerogel / microbead three-dimensional interpenetrating network; the phosphate layer forms a pyrophosphate network at high temperature to delay thermal decomposition, and the hollow structure of the microbead absorbs thermal stress through deformation during low-temperature shrinkage to cooperate with the gas barrier effect in the microbead. The prepared rubber has the effects of high temperature resistance, low temperature resistance and flame retardance.

Description

Technical Field

[0001] The present invention relates to the technical field of rubber materials, and particularly to a high and low temperature resistant rubber and a preparation method thereof. Background Art

[0002] As a kind of high molecular elastomer with polysiloxane as the main chain, silicone rubber is widely used in the fields of aerospace, electronic packaging, medical devices, etc. due to its excellent high and low temperature resistance, chemical inertness, biocompatibility and electrical insulation. However, its intrinsic molecular chain flexible structure and weak intermolecular force lead to insufficient mechanical properties, and the stability under extreme temperatures still faces challenges. Although the mechanical properties can be improved by adding reinforcing fillers such as fumed silica, uneven dispersion of the fillers is likely to cause stress concentration, and high filling amounts lead to poor processing fluidity, decreased elasticity and increased permanent deformation rate (up to 20% - 30% at high temperatures). In addition, the wear resistance and creep resistance of silicone rubber are poor, and surface wear and dimensional instability are likely to occur during long-term dynamic use.

[0003] In terms of high and low temperature resistance, although silicone rubber performs excellently in the conventional temperature range, there are still obvious shortcomings under extreme conditions. In terms of high temperature, when the temperature exceeds 250°C, the main chain of silicone rubber is prone to oxidative degradation, resulting in a sharp drop in mechanical properties, and at the same time, volatile small molecules are released, causing material shrinkage or cracking. When exposed to an environment above 150°C for a long time, the crosslinking network of silicone rubber will undergo thermogravimetric rearrangement, accelerating aging and failure. In terms of low temperature, although the glass transition temperature of silicone rubber is as low as -120°C, in actual applications, when the temperature is below -50°C, the elastic modulus rises sharply, resulting in the loss of flexibility, and seals are prone to failure due to embrittlement and cracking.

[0004] To address the above problems, the existing technologies mainly optimize the performance through chemical modification and nanocomposite, but still face technical bottlenecks. For example, phenyl silicone rubber can increase the upper temperature limit of heat resistance to 300°C, but the steric effect of phenyl groups increases the processing difficulty and further deteriorates the mechanical properties; although nanometer fillers can synergistically enhance the mechanical and heat resistance, poor interfacial compatibility is prone to cause agglomeration, and high aspect ratio fillers will significantly increase the hardness of the material, sacrificing elasticity. Summary of the Invention

[0005] The purpose of the present invention is to provide a high and low temperature resistant rubber and a preparation method thereof to solve the problems existing in the prior art.

[0006] To solve the above technical problems, the present invention provides the following technical solution: A high and low temperature resistant rubber, which is prepared by using a self-made aerogel / polyurethane hybrid filler to synergistically modify silicone rubber with hollow glass microspheres of phosphoric acid, and includes the following preparation steps:

[0007] (1) Immerse the aminated ceramic aerogel in a polyurethane prepolymer N,N-dimethylformamide solution with a concentration of 20%, add dibutyltin dilaurate accounting for 0.1 - 0.5% of the total mass of the reaction system, and permeate for 2 h under the conditions of a vacuum degree of 0.1 MPa and a temperature of 50°C; then add chain extender 1,4-butanediol with a molar ratio of isocyanate group to 1:1.05, and react at 60°C for 4 h; after the reaction is completed, wash the unreacted monomers with acetone and dry in vacuum at 60°C for 24 h with a vacuum degree of 10 mbar; then perform segmented ball milling on the aerogel / polyurethane polymer, and then dry at 60°C for 6 h to obtain hybrid filler with a particle size of 20 - 60 μm;

[0008] (2) Disperse the modified hollow glass microspheres in a phosphoric acid ethanol aqueous solution with a concentration of 10%, the volume ratio of ethanol to water is 7:3, then add dilute hydrochloric acid accounting for 0.4% of the mass of the phosphoric acid ethanol aqueous solution, and stir and react at 60°C for 6 h with a stirring speed of 60 rpm; after the reaction is completed, centrifuge for 10 min at a speed of 8000 rpm to collect the microspheres, wash with deionized water until neutral, and dry at 80°C for 6 h to obtain phosphoric acid hollow glass microspheres;

[0009] (3) Mix the polyurethane aerogel hybrid filler and the phosphoric acid hollow glass microspheres according to a mass ratio of 3 - 5:0.5 - 2, add a dispersant equivalent to 5% of the total mass of the filler, and perform high-speed shear dispersion at a speed of 2000 - 3000 rpm for 30 min at a temperature of 65 - 75°C; then thin-pass the silicone rubber base rubber 3 times on a two-roll open mill preheated to 50°C, and add the pre-dispersed mixed filler in batches; add bis(2,4-dichlorobenzoyl) peroxide accounting for 0.8 - 2.0% of the mass of the silicone rubber and continue mixing for 5 min; after placing the rubber compound in the mold, first defoam at -0.095 MPa for 10 min, and then perform secondary vulcanization to obtain the high and low temperature resistant rubber.

[0010] Further, the preparation method of the aminated ceramic aerogel in the step (1) is: immerse the ceramic aerogel in a KH550 ethanol solution with a concentration of 5%, the solid-liquid ratio is 1:20, perform ultrasonic treatment for 20 - 30 min, and set the power to 300 W; then dry in vacuum at 60°C for 12 h with a vacuum degree of 10 mbar to obtain an aerogel rich in amino groups on the surface.

[0011] Further, the preparation method of the polyurethane prepolymer in step (1) is as follows: isophorone diisocyanate and polyether polyol are dehydrated separately. Isophorone diisocyanate is dehydrated under vacuum at 80°C and -0.095 MPa until the water content is 0.05%, and polyether polyol is dehydrated under reduced pressure at 120°C and 0.098 MPa until the water content is 0.03%. Subsequently, under nitrogen protection, according to isocyanate: polyol = 2:1, isophorone diisocyanate is slowly added dropwise to polyether polyol, and polycondensation reaction is carried out by controlling the temperature at 80°C and continuously stirring for 24 h. After the reaction end point, the temperature is quickly lowered to below 40°C to terminate the reaction. After vacuum degassing at -0.095 MPa, filtering through a 5-10 μm filter screen, and adding 0.5% triphenyl phosphate of the total reactant mass as a stabilizer, the polyurethane prepolymer is obtained.

[0012] Further, the segmented ball milling method in step (1) is as follows: the ball-to-material ratio is 5-10:1, wet milling is carried out with zirconia balls using ethanol as the medium, the rotation speed is 300 rpm and ball milling is carried out for 2 h, then the speed is increased to 400 rpm and ball milling is carried out for another 2 h. After ball milling, centrifuge at 3000 rpm for 5 min.

[0013] Further, the mass ratio of the ceramic aerogel to the polyurethane prepolymer in step (1) is 1:2-5.

[0014] Further, the mass ratio of the hollow glass microspheres to the phosphoric acid ethanol solution in step (2) is 1:5-10.

[0015] Further, the preparation method of the modified hollow glass microspheres in step (2) is as follows: Hollow glass microspheres with a particle size of 20-50 μm and a wall thickness of 1-2 μm are mixed with a prepared sodium hydroxide solution with a mass fraction of 50% at a mass ratio of 1:10, put into a round-bottom flask, stirred in a water bath at 80°C for 8 h and then taken out, the stirring speed is 60 rpm, washed 4 times with distilled water, filtered and dried for 6 h at a temperature of 40°C to obtain pretreated hollow glass microspheres; Take KH-560, add it to 100 ml of absolute ethanol and mix evenly to prepare a 5% KH-560 aqueous solution, add 2% of the pretreated hollow glass microspheres of the aqueous solution mass, and the two are condensed and refluxed in a water bath at 80°C for 6 h. After the reaction is completed, wash 4 times with absolute ethanol to obtain modified hollow glass microspheres.

[0016] Further, the dispersant in step (3) is hydroxy silicone oil with a molecular weight of 2808.

[0017] Further, the filler is added in batches in step (3), and the total addition amount is 20-30% of the silicone rubber mass. The first addition amount is 50% of the total filler, the second addition amount accounts for 30% of the total filler, and the third addition amount accounts for 20% of the total filler.

[0018] Further, the two-stage vulcanization method in step (3) is as follows: one-stage vulcanization is carried out at 160 °C and a pressure of 10 MPa for 15 min, and then two-stage vulcanization is carried out in an atmospheric environment at 200 °C for 2 h to eliminate residual volatiles. After the two-stage vulcanization is completed, the temperature is cooled to room temperature at a rate of 5 °C / min, and left standing for 24-48 h to release residual thermal stress.

[0019] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0020] The present invention prepares an aerogel / polyurethane hybrid filler, and synergistically modifies silicone rubber with phosphoric acid hollow glass microspheres to achieve the effects of high temperature resistance, low temperature resistance, and flame retardancy.

[0021] First, polyurethane is combined with ceramic aerogel to form a semi-interpenetrating network to prepare a hybrid filler, which is added to silicone rubber; functional synergy is achieved through physical interpenetration and chemical bonding. Based on the design concept of material property complementarity, the polyether / polyester soft segment of polyurethane serves as a flexible chain segment, and still maintains the molecular chain segment movement ability at extremely low temperatures. The stress is dispersed through the dynamic recombination of hydrogen bonds, improving the low temperature resistance of silicone rubber; the polyurethane prepolymer penetrates into the pores of the aerogel and cures to form a flexible network to fill the rigid skeleton. The amino group on the surface of the aerogel reacts with the isocyanate group of polyurethane to form a covalent bond. The elastic buffering stress of polyurethane and the rigid skeleton support of the aerogel enable the composite material to have both high strength and high resilience; at the same time, the nanopores of the aerogel block gas heat conduction, and the polyurethane chain segments inhibit solid thermal vibration. The hybrid structure broadens the thermal stability temperature range; this "rigid-flexible interpenetration" design not only optimizes the compatibility between polyurethane and silicone rubber, but also improves the mechanical properties of silicone rubber;

[0022] Secondly, the phosphoric acid group undergoes nucleophilic addition with the epoxy group of the modified hollow glass microspheres, and then is added to silicone rubber for modification; the phosphate group forms hydrogen bonds with the chains in the silicone rubber, and at the same time, a condensation reaction may occur to form covalent bonds, enhancing the interfacial bonding force; the amino or hydroxyl group in the polyurethane can form hydrogen bonds with the phosphate group to increase the crosslinking density of the hybrid filler; the hydroxyl groups on the surface of the ceramic aerogel interact with the two hydrogen bonds generated by the combination to form a three-dimensional interpenetrating network of polyurethane / aerogel / microspheres; the phosphate layer forms a pyrophosphate network at high temperatures to delay thermal decomposition. The hollow structure of the microspheres absorbs thermal stress through deformation during low temperature shrinkage, and synergistically with the gas barrier effect inside the microspheres to prevent cracking of the silicone rubber matrix. Specific embodiments

[0023] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0024] To illustrate the method provided by the present invention more clearly, the following embodiments are used for detailed description. The test methods for various indexes of a high and low temperature resistant rubber prepared in the following embodiments are as follows:

[0025] Mechanical properties: The examples and comparative examples were tested using a GP-TS2000S universal tensile testing machine of Shenzhen Gaopin Testing Equipment Co., Ltd. in accordance with GB / T 528—2009 to test the tensile strength and elongation at break;

[0026] High temperature resistance: The silicone rubbers prepared in the examples and comparative examples of the present invention were cut into test samples that met the test specifications. Referring to the standard GB / T 528-2009, the tensile strength of the test samples after being treated in an oven at 350 °C for 6 h was tested. The tensile rate was set at 500 mm / min, and the strength retention rate was calculated to evaluate the high temperature resistance performance;

[0027] Low temperature resistance: The silicone rubbers prepared in the examples and comparative examples of the present invention were cut into test samples that met the test specifications. Referring to the standard GB / T 528-2009, the tensile strength of the test samples after being treated at -50 °C for 6 h was tested. The tensile rate was set at 500 mm / min, and the strength retention rate was calculated to evaluate the low temperature resistance performance;

[0028] Flame retardancy: The silicone rubbers prepared in the examples and comparative examples of the present invention were cut into test samples that met the test specifications, and the self-extinguishing time of the materials was measured in accordance with UL-94 respectively.

[0029] Example 1

[0030] (1) Dehydration treatments were carried out on isophorone diisocyanate and INOVOL R3001 polyether polyol respectively. Isophorone diisocyanate was dehydrated under vacuum at 80 °C and -0.095 MPa until the water content reached 0.05%, and polyether polyol was dehydrated under reduced pressure at 120 °C and 0.098 MPa until the water content reached 0.03%. Subsequently, under nitrogen protection, isophorone diisocyanate was slowly added dropwise to polyether polyol at an isocyanate: polyol ratio of 2:1, and polycondensation reaction was carried out by controlling the temperature at 80 °C and continuously stirring for 24 h. After the reaction end point, the temperature was rapidly cooled below 40 °C to terminate the reaction. After vacuum degassing at -0.095 MPa, filtration through a 5 μm filter, and addition of 0.5% triphenyl phosphate of the total reactant mass as a stabilizer, a polyurethane prepolymer was obtained. At room temperature, methacrylic acid and N,N-methylenebisacrylamide were dissolved in acetamide to obtain a mixed solution, in which the mass ratio of methacrylic acid to N,N-methylenebisacrylamide was 20:1, and 0.25 g of methacrylic acid was dissolved in each milliliter of acetamide. Silicon oxide ceramic powder and a dispersant were added to the mixed solution, and the pH value was adjusted to 7.5 and mixed evenly to obtain a suspension, in which the addition amount of silicon oxide ceramic powder was 25% of the total volume of the suspension, and the mass ratio of citric acid to silicon oxide ceramic powder was 2.5:100. An aqueous solution of ammonium persulfate with a concentration of 20% was added to the suspension and stirred evenly, in which the dosage of the aqueous solution of ammonium persulfate with a concentration of 20% was 5% of the total weight of the suspension. Then it was poured into the mold cavity, then heated to 70 °C and crosslinked and cured for 40 min, and demolded after natural cooling to room temperature and dried at 10 °C for 24 h to obtain a ceramic green body. The ceramic green body was placed in a debinding furnace and heated to 500 °C and kept for debinding for 80 h. The debound product was placed in a sintering furnace and sintered for 4.5 h under the conditions of sintering atmosphere and sintering temperature of 2000 °C, and then cooled to room temperature with the furnace to obtain a ceramic aerogel. The ceramic aerogel was immersed in a KH550 ethanol solution with a mass concentration of 5%, the solid-liquid ratio was 1:20, and ultrasonic treatment was carried out for 20 min with the power set at 300 W. Subsequently, it was vacuum dried at 60 °C for 12 h with a vacuum degree of 10 mbar to obtain an aerogel rich in amino groups on the surface. Then the amino-functionalized aerogel was immersed in a N,N-dimethylformamide solution of polyurethane prepolymer with a volume concentration of 20%, 0.1% dibutyltin dilaurate of the total mass of the reaction system was added, and the mass ratio of aerogel to polyurethane prepolymer was 1:2, and infiltration was carried out for 2 h under the conditions of a vacuum degree of 0.1 MPa and a temperature of 50 °C. Subsequently, it was added with a molar ratio of 1:1 to the isocyanate group.The chain extender 1,4-butanediol with a content of 0.5% was used to react at 60 °C for 4 h to cure the polyurethane prepolymer in the pores of the aerogel to form a semi-interpenetrating network. After the reaction was completed, the unreacted monomers were washed with acetone and vacuum-dried at 60 °C for 24 h with a vacuum degree of 10 mbar. Then, the aerogel / polyurethane polymer was ball-milled with a ball-to-material ratio of 5:1. Using ethanol as the medium and zirconia balls for wet milling, the milling was carried out at a speed of 300 rpm for 2 h, and then the speed was increased to 400 rpm and milled for another 2 h. After the ball milling was completed, it was centrifuged at 3000 rpm for 5 min and then dried at 60 °C for 6 h to obtain a hybrid filler with a particle size of 20 μm.

[0031] (2) Hollow glass microspheres with a particle size of 20 μm and a wall thickness of 1 μm were mixed with a sodium hydroxide solution with a prepared mass fraction of 50% at a mass ratio of 1:10, placed in a round-bottom flask, stirred in a water bath at 80 °C for 8 h, and then taken out. The stirring speed was 60 rpm. It was washed 4 times with distilled water and filtered and dried for 6 h at a temperature of 40 °C to obtain pretreated hollow glass microspheres. KH-560 was taken and added to 100 ml of absolute ethanol and mixed evenly to prepare a 5% aqueous solution of KH-560. 2% of the pretreated hollow glass microspheres by mass of the aqueous solution were added, and the two were refluxed and condensed in a water bath at 80 °C for 6 h. After the reaction was completed, it was washed 4 times with absolute ethanol to obtain modified hollow glass microspheres. The modified hollow glass microspheres were dispersed in a phosphoric acid ethanol aqueous solution with a concentration of 10%, and the volume ratio of ethanol to water was 7:3. Then, dilute hydrochloric acid with a content of 0.4% by mass of the phosphoric acid ethanol aqueous solution was added, and the mass ratio of the hollow glass microspheres to the phosphoric acid ethanol solution was 1:5. It was stirred and reacted at 60 °C for 6 h with a stirring speed of 60 rpm to make the phosphoric acid group undergo nucleophilic addition with the epoxy group on the surface of the microspheres. After the reaction was completed, the microspheres were collected by centrifugation at a speed of 8000 rpm for 10 min, washed with deionized water until neutral, and dried at 80 °C for 6 h to obtain phosphoric acid hollow glass microspheres.

[0032] (3) Hybridize the polyurethane aerogel filler with hollow glass microspheres of phosphoric acid at a mass ratio of 3:0.5, add hydroxyl silicone oil equivalent to 5% of the total mass of the filler as a dispersant, and disperse it by high-speed shearing at a speed of 2000 rpm for 30 min at a temperature of 65 °C; then pass the silicone rubber base gum thinly through a two-roll mill preheated to 50 °C three times. The silicone rubber base gum is methyl vinyl silicone rubber 110-2 from Jiangxi Xinghuo Organosilicon Plant. Add the pre-dispersed mixed filler in batches, with a total addition amount of 20% of the mass of the silicone rubber. The first addition amount is 50% of the total filler, the second addition amount accounts for 30% of the total filler, and the third addition amount accounts for 20% of the total filler; Knead for 15 min and add bis(2,4-dichlorobenzoyl) peroxide at 0.8% of the mass of the silicone rubber, and continue kneading for 5 min; After placing the rubber compound in the mold, first defoam it at -0.095 MPa for 10 min, then perform primary vulcanization at 160 °C and a pressure of 10 MPa for 15 min, and then perform secondary vulcanization in an atmospheric environment at 200 °C for 2 h to eliminate residual volatiles. After the secondary vulcanization is completed, cool it to room temperature at a rate of 5 °C / min and let it stand for 24 h to release the residual thermal stress to obtain the high and low temperature resistant rubber.

[0033] Example 2

[0034] (1) The isophorone diisocyanate and INOVOL R3001 polyether polyol were dehydrated separately. The isophorone diisocyanate was dehydrated under vacuum at 80 °C and -0.095 MPa until the water content reached 0.05%. The polyether polyol was dehydrated under reduced pressure at 120 °C and 0.098 MPa until the water content reached 0.03%. Subsequently, under nitrogen protection, the isophorone diisocyanate was slowly added dropwise to the polyether polyol at an isocyanate:polyol ratio of 2:1, and polycondensation reaction was carried out by controlling the temperature at 80 °C and continuously stirring for 24 h. After the reaction end point, the temperature was rapidly cooled below 40 °C to terminate the reaction. After vacuum degassing at -0.095 MPa, filtration through a 7.5 μm filter, and addition of 0.5% triphenyl phosphate based on the total mass of the reactants as a stabilizer, a polyurethane prepolymer was obtained. At room temperature, methacrylic acid and N,N-methylenebisacrylamide were dissolved in acetamide to obtain a mixed solution, where the mass ratio of methacrylic acid to N,N-methylenebisacrylamide was 20:1, and 0.25 g of methacrylic acid was dissolved in each milliliter of acetamide. Silicon oxide ceramic powder and a dispersant were added to the mixed solution, and the pH value was adjusted to 7.5 and mixed evenly to obtain a suspension, where the addition amount of the silicon oxide ceramic powder was 25% of the total volume of the suspension, and the mass ratio of citric acid to the silicon oxide ceramic powder was 2.5:100. An aqueous solution of ammonium persulfate with a concentration of 20% was added to the suspension and stirred evenly, where the amount of the aqueous solution of ammonium persulfate with a concentration of 20% was 5% of the total weight of the suspension. Then it was poured into the mold cavity, then heated to 70 °C, and crosslinked and cured for 40 min. After natural cooling to room temperature, demolding was carried out, and drying was carried out at 10 °C for 24 h to obtain a ceramic green body. The ceramic green body was placed in a debinding furnace and heated to 500 °C for 80 h of heat preservation and debinding. The debound product was placed in a sintering furnace and sintered for 4.5 h under the conditions of a sintering atmosphere and a sintering temperature of 2000 °C, and then cooled to room temperature with the furnace to obtain a ceramic aerogel. The ceramic aerogel was immersed in a 5% KH550 ethanol solution with a solid-liquid ratio of 1:20 and ultrasonically treated for 25 min with a power setting of 300 W. Subsequently, vacuum drying was carried out at 60 °C for 12 h with a vacuum degree of 10 mbar to obtain an aerogel rich in amino groups on the surface. Then the amino-functionalized aerogel was immersed in a 20% polyurethane prepolymer N,N-dimethylformamide solution, and dibutyltin dilaurate with 0.3% of the total mass of the reaction system was added. The mass ratio of the aerogel to the polyurethane prepolymer was 1:3.5, and infiltration was carried out under the conditions of a vacuum degree of 0.1 MPa and a temperature of 50 °C for 2 h. Subsequently, a chain extender 1,4-butanediol with a molar ratio of 1:1.05 to the isocyanate group was added and reacted at 60 °C for 4 h to cause the polyurethane prepolymer to cure in the pores of the aerogel to form a semi-interpenetrating network. After the reaction was completed, the unreacted monomers were washed with acetone, and vacuum drying was carried out at 60 °C for 24 h with a vacuum degree of 10 mbar. Then the aerogel / polyurethane polymer was ball-milled with a ball-to-material ratio of 7.5:1, using ethanol as the medium and zirconia balls for wet grinding, grinding at a speed of 350 rpm for 2 h, then increasing the speed to 400 rpm and grinding for another 2 h; after the grinding is completed, centrifuge at 3000 rpm for 5 min, and then dry at 60 °C for 6 h to obtain hybrid filler with a particle size of 40 μm.

[0035] (2) Mix hollow glass microspheres with a particle size of 35 μm and a wall thickness of 1.5 μm and sodium hydroxide solution with a prepared mass fraction of 50% at a mass ratio of 1:10, put them into a round-bottom flask, stir in a water bath at 80 °C for 8 h and then take out, the stirring speed is 60 rpm, wash 4 times with distilled water, filter and dry for 6 h at a temperature of 40 °C to obtain pretreated hollow glass microspheres; take KH-560, add it to 100 ml of anhydrous ethanol and mix evenly to prepare a 5% KH-560 aqueous solution, add 2% of the pretreated hollow glass microspheres by the mass of the aqueous solution, and the two are condensed and refluxed in a water bath at 80 °C for 6 h. After the reaction is completed, wash 4 times with anhydrous ethanol to obtain modified hollow glass microspheres; disperse the modified hollow glass microspheres in a 10% phosphoric acid ethanol aqueous solution with a volume ratio of ethanol to water of 7:3, then add 0.4% of dilute hydrochloric acid by the mass of the phosphoric acid ethanol aqueous solution, and the mass ratio of the hollow glass microspheres to the phosphoric acid ethanol solution is 1:7.5, stir and react at 60 °C for 6 h, the stirring speed is 60 rpm, so that the phosphate group undergoes nucleophilic addition with the epoxy group on the microsphere surface; after the reaction is completed, centrifuge at a speed of 8000 rpm for 10 min to collect the microspheres, wash with deionized water until neutral, and dry at 80 °C for 6 h to obtain phosphoric acid hollow glass microspheres;

[0036] (3) Mix the polyurethane aerogel hybrid filler and the phosphoric acid hollow glass microspheres at a mass ratio of 4:1.25, add hydroxyl silicone oil equivalent to 5% of the total mass of the filler as a dispersant, and disperse at a high speed of 2500 rpm for 30 min at a temperature of 70 °C; then thin-pass the silicone rubber base gum 3 times on a two-roll mill preheated to 50 °C. The silicone rubber base gum is methyl vinyl silicone rubber 110-2 from Jiangxi Xinghuo Organosilicon Plant. Add the pre-dispersed mixed filler in batches, and the total addition amount is 25% of the mass of the silicone rubber. The first addition amount is 50% of the total filler, the second addition amount accounts for 30% of the total filler, and the third addition amount accounts for 20% of the total filler; knead for 15 min and add 1.4% of bis(2,4-dichlorobenzoyl) peroxide by the mass of the silicone rubber, and continue kneading for 5 min; after putting the rubber compound into the mold, first defoam at -0.095 MPa for 10 min, then carry out one-stage vulcanization at 160 °C and 10 MPa for 15 min, and then carry out two-stage vulcanization at 200 °C in an atmospheric environment for 2 h to eliminate residual volatiles. After the two-stage vulcanization is completed, cool down to room temperature at a rate of 5 °C / min, and stand for 36 h to release the residual thermal stress to obtain the high and low temperature resistant rubber.

[0037] Example 3

[0038] (1) The isophorone diisocyanate and the INOVOL R3001 polyether polyol are dehydrated respectively. The isophorone diisocyanate is dehydrated under vacuum at 80°C and -0.095 MPa until the water content is 0.05%. The polyether polyol is dehydrated under reduced pressure at 120°C and 0.098 MPa until the water content is 0.03%. Subsequently, under nitrogen protection, according to the ratio of isocyanate: polyol = 2:1, the isophorone diisocyanate is slowly added dropwise to the polyether polyol, and polycondensation reaction is carried out by controlling the temperature at 80°C and continuously stirring for 24 h. After the end point of the reaction, the temperature is quickly cooled below 40°C to terminate the reaction. After vacuum degassing at -0.095 MPa, filtering through a 10-μm filter screen, and adding 0.5% triphenyl phosphate of the total reactant mass as a stabilizer, a polyurethane prepolymer is obtained. At room temperature, methacrylic acid and N,N-methylenebisacrylamide are dissolved in acetamide to obtain a mixed solution, in which the mass ratio of methacrylic acid to N,N-methylenebisacrylamide is 20:1, and 0.25 g of methacrylic acid is dissolved in each milliliter of acetamide. Silicon oxide ceramic powder and a dispersant are added to the mixed solution, the pH value is adjusted to 7.5, and it is mixed evenly to obtain a suspension, in which the addition amount of the silicon oxide ceramic powder is 25% of the total volume of the suspension, and the mass ratio of citric acid to the silicon oxide ceramic powder is 2.5:100. An aqueous solution of ammonium persulfate with a concentration of 20% is added to the suspension and stirred evenly, in which the amount of the aqueous solution of ammonium persulfate with a concentration of 20% is 5% of the total weight of the suspension. Then it is poured into the mold cavity, then heated to 70°C, and crosslinked and cured for 40 min. After natural cooling to room temperature, it is demolded and dried at 10°C for 24 h to obtain a ceramic green body. The ceramic green body is placed in a debinding furnace and heated to 500°C for 80 h of heat preservation and debinding. The debound product is placed in a sintering furnace and sintered for 4.5 h under the conditions of a sintering atmosphere and a sintering temperature of 2000°C, and then cooled to room temperature with the furnace, and a ceramic aerogel is obtained. The ceramic aerogel is immersed in a 5% KH550 ethanol solution, the solid-liquid ratio is 1:20, and ultrasonic treatment is carried out for 30 min with the power set at 300 W. Subsequently, it is vacuum dried at 60°C for 12 h with a vacuum degree of 10 mbar to obtain an aerogel rich in amino groups on the surface. Then the amino-functionalized aerogel is immersed in a 20% polyurethane prepolymer N,N-dimethylformamide solution, 0.5% dibutyltin dilaurate of the total mass of the reaction system is added, and the mass ratio of the aerogel to the polyurethane prepolymer is 1:5, and it is infiltrated for 2 h under the conditions of a vacuum degree of 0.1 MPa and a temperature of 50°C. Subsequently, add with a molar ratio of 1:1 to the isocyanate group.The chain extender 1,4-butanediol of 0.5 was reacted at 60 °C for 4 h to cure the polyurethane prepolymer in the pores of the aerogel to form a semi-interpenetrating network; after the reaction was completed, the unreacted monomers were washed with acetone and dried in vacuo at 60 °C for 24 h, and the vacuum degree was 10 mbar; then the aerogel / polyurethane polymer was ball-milled with a ball-to-material ratio of 10:1, wet-milled with zirconia balls using ethanol as the medium at a rotation speed of 400 rpm for 2 h; after the ball milling was completed, centrifuged at 3000 rpm for 5 min, and then dried at 60 °C for 6 h to obtain a hybrid filler with a particle size of 60 μm;.

[0039] (2) Hollow glass microspheres with a particle size of 50 μm and a wall thickness of 2 μm were mixed with a sodium hydroxide solution with a prepared mass fraction of 50% at a mass ratio of 1:10, placed in a round-bottom flask, stirred in a water bath at 80 °C for 8 h, then taken out, the stirring speed was 60 rpm, washed 4 times with distilled water, filtered and dried for 6 h at a temperature of 40 °C to obtain pretreated hollow glass microspheres; KH-560 was taken and added to 100 ml of absolute ethanol and mixed evenly to prepare a 5% aqueous solution of KH-560, and 2% of the pretreated hollow glass microspheres by mass of the aqueous solution was added, and the two were refluxed in a water bath at 80 °C for 6 h. After the reaction was completed, washed 4 times with absolute ethanol to obtain modified hollow glass microspheres; the modified hollow glass microspheres were dispersed in a phosphoric acid ethanol aqueous solution with a concentration of 10%, the volume ratio of ethanol to water was 7:3, and then 0.4% of dilute hydrochloric acid by mass of the phosphoric acid ethanol aqueous solution was added, and the mass ratio of the hollow glass microspheres to the phosphoric acid ethanol solution was 1:10, stirred and reacted at 60 °C for 6 h, and the stirring speed was 60 rpm to make the phosphoric acid group and the epoxy group on the microsphere surface undergo nucleophilic addition; after the reaction was completed, the microspheres were collected by centrifugation at a speed of 8000 rpm for 10 min, washed with deionized water until neutral, and dried at 80 °C for 6 h to obtain phosphoric acid hollow glass microspheres;

[0040] (3) Mix the polyurethane aerogel hybrid filler and hollow glass microspheres of phosphoric acid at a mass ratio of 5:2, add hydroxyl silicone oil equivalent to 5% of the total mass of the filler as a dispersant, and disperse them by high-speed shearing at a speed of 3000 rpm for 30 min at a temperature of 75 °C; then pass the silicone rubber base gum thinly through a two-roll mill preheated to 50 °C three times. The silicone rubber base gum is methyl vinyl silicone rubber 110-2 from Jiangxi Xinghuo Organosilicon Plant. Add the pre-dispersed mixed filler in batches, with the total addition amount being 30% of the mass of the silicone rubber. The first addition amount is 50% of the total filler, the second addition amount accounts for 30% of the total filler, and the third addition amount accounts for 20% of the total filler; after kneading for 15 min, add bis(2,4-dichlorobenzoyl) peroxide equivalent to 2.0% of the mass of the silicone rubber and continue kneading for 5 min; after placing the rubber compound into the mold, first degas it at -0.095 MPa for 10 min, then carry out primary vulcanization at 160 °C and 10 MPa for 15 min, and then carry out secondary vulcanization in an atmospheric environment at 200 °C for 2 h to eliminate residual volatiles. After the secondary vulcanization is completed, cool it to room temperature at a rate of 5 °C / min, and let it stand for 48 h to release the residual thermal stress to obtain the high and low temperature resistant rubber.

[0041] Comparative Example 1

[0042] The difference between Comparative Example 1 and Example 2 is that step (1) is not included, and step (3) is changed to: Mix polyurethane and hollow glass microspheres of phosphoric acid at a mass ratio of 4:1.25, add hydroxyl silicone oil equivalent to 5% of the total mass of the filler as a dispersant, and disperse them by high-speed shearing at a speed of 2500 rpm for 30 min at a temperature of 70 °C; then pass the silicone rubber base gum thinly through a two-roll mill preheated to 50 °C three times. The silicone rubber base gum is methyl vinyl silicone rubber 110-2 from Jiangxi Xinghuo Organosilicon Plant. Add the pre-dispersed mixed filler in batches, with the total addition amount being 25% of the mass of the silicone rubber. The first addition amount is 50% of the total filler, the second addition amount accounts for 30% of the total filler, and the third addition amount accounts for 20% of the total filler; after kneading for 15 min, add bis(2,4-dichlorobenzoyl) peroxide equivalent to 1.4% of the mass of the silicone rubber and continue kneading for 5 min; after placing the rubber compound into the mold, first degas it at -0.095 MPa for 10 min, then carry out primary vulcanization at 160 °C and 10 MPa for 15 min, and then carry out secondary vulcanization in an atmospheric environment at 200 °C for 2 h to eliminate residual volatiles. After the secondary vulcanization is completed, cool it to room temperature at a rate of 5 °C / min, and let it stand for 36 h to release the residual thermal stress to obtain the high and low temperature resistant rubber; the remaining steps are the same as those in Example 2.

[0043] Comparative Example 2

[0044] The difference between Comparative Example 2 and Example 2 lies in the differences in steps (1) and (3). Steps (1) and (3) are changed to: (1) Immerse the ceramic aerogel in a KH550 ethanol solution with a concentration of 5%, the solid-liquid ratio is 1:20, ultrasonically treat for 25 min, and set the power to 300 W; then vacuum dry at 60 °C for 12 h, and the vacuum degree is 10 mbar to obtain an aerogel rich in amino groups on the surface;

[0045] (3) Mix the aerogel rich in amino groups on the surface with hollow glass microspheres of phosphoric acid in a mass ratio of 4:1.25, add hydroxyl silicone oil equivalent to 5% of the total mass of the fillers as a dispersant, and shear and disperse at a high speed of 2500 rpm for 30 min, and the temperature is 70 °C; then thin-pass the silicone rubber base gum 3 times on a two-roll open mill preheated to 50 °C. The silicone rubber base gum is methyl vinyl silicone rubber 110-2 from Jiangxi Xinghuo Organosilicon Plant. Add the pre-dispersed mixed fillers in batches, and the total addition amount is 25% of the mass of the silicone rubber. The first addition amount is 50% of the total fillers, the second addition amount accounts for 30% of the total fillers, and the third addition amount accounts for 20% of the total fillers; Knead for 15 min and add 1.4% of bis(2,4-dichlorobenzoyl) peroxide based on the mass of the silicone rubber, and continue to knead for 5 min; After placing the rubber compound in the mold, first defoam at -0.095 MPa for 10 min, then carry out primary vulcanization at 160 °C and 10 MPa for 15 min, and then carry out secondary vulcanization in an atmospheric environment at 200 °C for 2 h to eliminate residual volatiles. After the secondary vulcanization is completed, cool down to room temperature at a rate of 5 °C / min, and let it stand for 36 h to release the residual thermal stress to obtain a high and low temperature resistant rubber; the remaining steps are the same as those in Example 2.

[0046] Comparative Example 3

[0047] The difference between Comparative Example 3 and Example 2 is that step (2) is absent, and step (3) is modified as follows: Mix the polyurethane aerogel hybrid filler with 5% of the total filler mass of hydroxyl silicone oil, and disperse it by high-speed shearing at a speed of 2500 rpm for 30 min at a temperature of 70°C; subsequently, pass the silicone rubber base gum thinly through a two-roll mill preheated to 50°C three times. The silicone rubber base gum is methyl vinyl silicone rubber 110-2 from Jiangxi Xinghuo Organosilicon Plant. Add the pre-dispersed mixed filler in batches, with the total addition amount being 25% of the silicone rubber mass. The first addition amount is 50% of the total filler, the second addition amount accounts for 30% of the total filler, and the third addition amount accounts for 20% of the total filler; after kneading for 15 min, add 1.4% of the silicone rubber mass of bis(2,4-dichlorobenzoyl) peroxide, and continue kneading for 5 min; after placing the rubber compound into the mold, first defoam it at -0.095 MPa for 10 min, and then perform primary vulcanization at 160°C and 10 MPa for 15 min, and then perform secondary vulcanization for 2 h in an atmospheric environment at 200°C to eliminate residual volatiles. After the secondary vulcanization is completed, cool it to room temperature at a rate of 5°C / min, and let it stand for 36 h to release the residual thermal stress to obtain the high and low temperature resistant rubber; the remaining steps are the same as those in Example 2.

[0048] Comparative Example 4

[0049] The difference between Comparative Example 4 and Example 2 is that step (2) is absent, and step (3) is modified as follows: Mix the polyurethane aerogel hybrid filler with hollow glass microspheres having a particle size of 35 μm and a wall thickness of 1.5 μm at a mass ratio of 4:1.25, add 5% of the total filler mass of hydroxyl silicone oil as a dispersant, and disperse it by high-speed shearing at a speed of 2500 rpm for 30 min at a temperature of 70°C; subsequently, pass the silicone rubber base gum thinly through a two-roll mill preheated to 50°C three times. The silicone rubber base gum is methyl vinyl silicone rubber 110-2 from Jiangxi Xinghuo Organosilicon Plant. Add the pre-dispersed mixed filler in batches, with the total addition amount being 25% of the silicone rubber mass. The first addition amount is 50% of the total filler, the second addition amount accounts for 30% of the total filler, and the third addition amount accounts for 20% of the total filler; after kneading for 15 min, add 1.4% of the silicone rubber mass of bis(2,4-dichlorobenzoyl) peroxide, and continue kneading for 5 min; after placing the rubber compound into the mold, first defoam it at -0.095 MPa for 10 min, and then perform primary vulcanization at 160°C and 10 MPa for 15 min, and then perform secondary vulcanization for 2 h in an atmospheric environment at 200°C to eliminate residual volatiles. After the secondary vulcanization is completed, cool it to room temperature at a rate of 5°C / min, and let it stand for 36 h to release the residual thermal stress to obtain the high and low temperature resistant rubber; the remaining steps are the same as those in Example 2.

[0050] Comparative Example 5

[0051] The difference between Comparative Example 5 and Example 2 is that step (1) is absent, and step (3) is modified as follows: Take hollow glass microspheres of phosphoric acid and hydroxy silicone oil equivalent to 1% of the total mass of the microspheres as a dispersant, and perform high-speed shear dispersion at a rotation speed of 2500 rpm for 30 min at a temperature of 70°C; subsequently, pass the silicone rubber base stock thinly through a two-roll mill preheated to 50°C three times. The silicone rubber base stock is methyl vinyl silicone rubber 110-2 from Jiangxi Xinghuo Organosilicon Plant. Add the pre-dispersed hollow glass microspheres of phosphoric acid in batches, with a total addition amount of 25% of the mass of the silicone rubber. The first addition amount is 50% of the hollow glass microspheres of phosphoric acid, the second addition amount accounts for 30% of the hollow glass microspheres of phosphoric acid, and the third addition amount accounts for 20% of the hollow glass microspheres of phosphoric acid; after kneading for 15 min, add bis(2,4-dichlorobenzoyl) peroxide accounting for 1.4% of the mass of the silicone rubber, and continue kneading for 5 min; after placing the rubber compound into a mold, first defoam at -0.095 MPa for 10 min, then perform primary vulcanization at 160°C and a pressure of 10 MPa for 15 min, and then perform secondary vulcanization in an atmospheric environment at 200°C for 2 h to eliminate residual volatiles. After the secondary vulcanization is completed, cool down to room temperature at a rate of 5°C / min, and let it stand for 36 h to release residual thermal stress to obtain a high and low temperature resistant rubber; the remaining steps are the same as those in Example 2.

[0052] Effect Example

[0053] The following Table 1 shows the performance analysis results of a high and low temperature resistant rubber using Examples 1 to 3 and Comparative Examples 1 to 5 of the present invention.

[0054] Table 1

[0055]

[0056]

[0057] From the comparison of the experimental data of low-temperature resistance between the examples and the comparative examples, it can be found that in the present invention, polyurethane and ceramic aerogel are combined to form a semi-interpenetrating network to prepare a hybrid filler, which is added to silicone rubber; through physical interpenetration and chemical bonding, functional synergy is achieved. Based on the design concept of material property complementarity, the polyether / polyester soft segment of polyurethane, as a flexible chain segment, still maintains the molecular chain segment movement ability at extremely low temperatures, and disperses stress through dynamic recombination of hydrogen bonds, thereby improving the low-temperature resistance of silicone rubber. From the comparison of the experimental data of tensile strength and elongation at break between the examples and the comparative examples, it can be found that in the present invention, the polyurethane prepolymer penetrates into the pores of the aerogel and cures to form a flexible network to fill the rigid skeleton. The amino group on the surface of the aerogel reacts with the isocyanate group of polyurethane to form a covalent bond. The elastic buffering stress of polyurethane and the rigid skeleton support of the aerogel enable the composite material to have both high strength and high resilience. The phosphate group undergoes nucleophilic addition with the epoxy group of the hollow glass microspheres and is then added to silicone rubber for modification; the phosphate ester group forms hydrogen bonds with the chains in silicone rubber, and at the same time, a condensation reaction may occur to form covalent bonds, enhancing the interfacial binding force; the amino group or hydroxyl group in polyurethane can form hydrogen bonds with the phosphate ester group to increase the crosslinking density of the hybrid filler; the hydroxyl groups on the surface of the ceramic aerogel interact with the two hydrogen bonds generated by the combination to form a three-dimensional interpenetrating network of polyurethane / aerogel / microspheres. From the comparison of the experimental data of high-temperature resistance between the examples and the comparative examples, it can be found that in the present invention, the nano-pores of the aerogel block gas heat conduction, the polyurethane chain segments inhibit solid thermal vibration, and the hybrid structure broadens the thermal stability temperature range; this "rigid-flexible interpenetrating" design not only optimizes the compatibility between polyurethane and silicone rubber, but also improves the mechanical properties of silicone rubber. From the comparison of the experimental data of self-extinguishing time between the examples and the comparative examples, it can be found that in the present invention, the phosphate ester layer forms a pyrophosphate network at high temperatures to delay thermal decomposition. The hollow structure of the microspheres absorbs thermal stress through deformation during low-temperature shrinkage, and cooperates with the gas barrier effect inside the microspheres to prevent cracking of the silicone rubber matrix.

[0058] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be construed as limiting the claims involved.

Claims

1. A high and low temperature resistant rubber, characterized in that: The rubber is a self-made aerogel / polyurethane hybrid filler, prepared by cooperating with phosphoric acid hollow glass microspheres to modify silicone rubber, and includes the following preparation steps: (1) The amino ceramic aerogel is immersed in a 20% polyurethane prepolymer N,N-dimethylformamide solution, and 0.1-0.5% of dibutyltin dilaurate based on the total mass of the reaction system is added, and the mixture is infiltrated for 2 hours at a vacuum degree of 0.1 MPa and a temperature of 50°C; then, a chain extender 1,4-butanediol is added at a molar ratio of 1:1.05 to isocyanate group, and the mixture is reacted at 60°C for 4 hours; after the reaction is completed, the mixture is washed with acetone, and vacuum dried at 60°C for 24 hours with a vacuum degree of 10 mbar; then, the aerogel / polyurethane is ball-milled in sections, and then dried at 60°C for 6 hours to obtain a hybrid filler with a particle size of 20-60 μm; (2) The modified hollow glass microspheres were dispersed in a 10% phosphoric acid ethanol aqueous solution, with a volume ratio of ethanol to water of 7:3, and then 0.4% of the solution mass of dilute hydrochloric acid was added, and the reaction was stirred at 60°C for 6 hours at a stirring speed of 60 rpm; after the reaction was completed, the microspheres were collected by centrifugation at a speed of 8000 rpm for 10 minutes, washed with deionized water until neutral, and dried at 80°C for 6 hours to obtain phosphoric acid hollow glass microspheres; (3) The hybrid filler and the phosphoric acid hollow glass microspheres are mixed in a mass ratio of 3-5:0.5-2, and a dispersant equivalent to 5% of the total mass of the filler is added, and the mixture is dispersed at a speed of 2000-3000 rpm for 30 minutes at a temperature of 65-75°C; then, the silicone rubber base is thinly passed through a two-roll open mill at 50°C for 3 times, and the pre-dispersed mixed filler is added in batches; after mixing for 15 minutes, 0.8-2.0% of the mass of the silicone rubber is added with bis-2,4-dichlorobenzoyl peroxide, and mixing is continued for 5 minutes; after placing the rubber compound into a mold, it is first degassed at -0.095 MPa for 10 minutes, and then two-stage vulcanization is performed to obtain a high and low temperature resistant rubber.

2. The high and low temperature resistant rubber according to claim 1, characterized in that: In the step (1), the aminated ceramic aerogel is prepared by modifying the ceramic aerogel with KH550.

3. The high and low temperature resistant rubber according to claim 1, characterized in that: The segmented ball milling method in step (1) is as follows: the ball-to-material ratio is 5-10:1, ethanol is used as the medium, zirconium oxide balls are used for wet milling, the speed is 300 rpm for 2 hours, and then the speed is increased to 400 rpm and ball milled for another 2 hours; after the ball milling is completed, centrifuge at 3000 rpm for 5 minutes.

4. The high and low temperature resistant rubber according to claim 1, characterized in that: In the step (1), the mass ratio of the ceramic aerogel to the polyurethane prepolymer is 1:2-5.

5. The high and low temperature resistant rubber according to claim 1, characterized in that: In the step (2), the mass ratio of the hollow glass microspheres to the phosphoric acid ethanol solution is 1:5-10.

6. The high and low temperature resistant rubber according to claim 1, characterized in that: In the step (2), the modified hollow glass microspheres are pretreated with sodium hydroxide and then modified with KH-560 to obtain the modified hollow glass microspheres.

7. The high and low temperature resistant rubber according to claim 1, characterized in that: The dispersant in step (3) is hydroxy silicone oil with a molecular weight of 2808.

8. The high and low temperature resistant rubber according to claim 1, characterized in that: In the step (3), fillers are added in batches, with the total addition amount being 20-30% of the mass of the silicone rubber, the first addition amount being 50% of the total fillers, the second addition amount being 30% of the total fillers, and the third addition amount being 20% ​​of the total fillers.

9. The high and low temperature resistant rubber according to claim 1, characterized in that: The two-stage vulcanization method in step (3) is: a first-stage vulcanization is performed at 160° C. and 10 MPa pressure for 15 minutes, and a second-stage vulcanization is performed at 200° C. and normal pressure for 2 hours to eliminate residual volatiles. After the second-stage vulcanization is completed, the temperature is lowered to room temperature at a rate of 5° C. / min and left to stand for 24-48 hours to release residual thermal stress.

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