A phenolic resin modified silicone rubber ablation-resistant coating material and its preparation method and application

Abstract

The present invention discloses a phenolic resin modified silicone rubber ablation-resistant coating material, a preparation method and an application thereof, and belongs to the field of solid rocket engine manufacturing. The phenolic resin modified silicone rubber for ablation-resistant heat-resistant coating disclosed in the present invention is obtained by mechanically compounding and thermally vulcanizing a phenolic resin modified with silicone oil and silicone rubber. The present invention utilizes the chemical reaction between isocyanate and hydroxyl to combine the phenolic resin and silicone oil, and the phenolic resin modified with silicone oil is easier to be highly and stably dispersed in the silicone rubber. The phenolic resin modified with silicone rubber has a high carbonization rate and excellent mechanical properties. The composite material prepared with it as a matrix has a very low mass ablation rate and linear ablation rate, and is expected to be used for internal and external thermal protection of solid rocket engines.

Description

Technical Field

[0001] The invention belongs to the technical field of silicone rubber and resin, and particularly relates to a phenolic resin modified silicone rubber ablation-resistant coating material, a preparation method and an application thereof. Background Art

[0002] The internal insulation layer of a solid rocket motor protects the motor casing from the high-temperature gases produced by propellant combustion. Furthermore, it must withstand the various stresses induced by the motor during operation. Therefore, the insulation material used in this motor generally requires properties such as low thermal conductivity, low density, low elastic modulus, and high elongation. Furthermore, due to its harsh service environment, the insulation material must be both flexible and ablation-resistant. Among various polymer materials, silicone rubber, with its excellent thermal stability, toughness, and low glass transition temperature, is a promising matrix material for the thermal insulation layer of solid rocket motors. However, silicone rubber's low carbon content, resulting in a low degree of carbonization at high temperatures, and its poor mechanical properties severely limit its application in ablation conditions. Improving the ablation resistance and mechanical properties of silicone rubber through chemical or physical modification is currently a key challenge. Selecting fillers that combine ablation resistance with excellent mechanical properties to modify silicone rubber is also a current research hotspot. Phenolic resin is widely used due to its readily available raw materials, low cost, and excellent dimensional stability and ablation resistance. Although phenolic resin has been used to improve the ablation resistance of EPDM, nitrile rubber and silicone rubber, the modification effect is not ideal because the phenolic resin is not highly dispersed.

[0003] At present, there have been many studies on the use of phenolic resin to modify silicone rubber. The use of coupling agents to connect phenolic epoxy resin and silicone rubber can improve its mechanical strength and improve its bonding strength (Journal of Macromolecular Science, Part A, 2019, 56 (5): 506-512.). The Chinese patent application with publication number CN103601892A discloses a new type of fireproof silicone rubber material. By introducing organic groups containing benzene rings into silicone rubber, the characteristics of the high carbon content of phenolic resin are utilized to adjust the ablation resistance and self-adhesion through the main structure. However, this solution does not overcome the defective problem of poor mechanical properties of silicone rubber itself. Although the incorporation of phenolic hollow microspheres into silicone rubber can also improve the ablation performance of the composite material, the effect is not significant (Polymers, 2022, 14 (18): 3846). Chinese patent publication number CN109535727A discloses a method for preparing a silicone rubber thermal insulation composite material. The silicone rubber thermal insulation composite material is mainly composed of white carbon black, phenolic resin, carbon fiber, and a silicone rubber matrix. The addition of phenolic resin significantly improves the ablation resistance and mechanical properties of the silicone rubber. However, the amount of phenolic resin introduced into the system is very low, and the flexibility of the silicone rubber is sacrificed. Chinese patent publication number CN109265684A discloses a novel method for modifying silicone rubber with phenolic resin. By adding brominated phenolic resin to silicone rubber, the problem of easy pulverization during the traditional silicone rubber ablation process is solved, while its mechanical properties are improved. However, this chemical grafting modification method has harsh reaction conditions and requires the consumption of a large amount of organic solvent. By hydrosilylation, allyl ether phenolic resin is grafted onto silicone rubber with Si-H groups. Although the compatibility of the two is effectively improved, the synthesis process involved is complicated and there are strict restrictions on the amount of phenolic resin (Journal of Applied Polymer Science, 2020, 137 (6): 48353). It can be seen that the existing modification methods have some shortcomings. This is because there is a difference in polarity between silicone rubber and phenolic resin, and the compatibility is poor, which makes it difficult to improve the quality retention rate and mechanical properties of silicone rubber itself at high temperatures.

[0004] In summary, a new method is urgently needed to introduce phenolic resin into silicone rubber to improve the compatibility of phenolic resin and silicone rubber, and to improve the ablation resistance and mechanical properties of silicone rubber itself so that it can adapt to the high heat flow environment of the inner insulation layer material. Summary of the Invention

[0005] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a phenolic resin modified silicone rubber ablation-resistant coating material and its preparation method and application, so as to solve the technical problem that the existing phenolic resin modified silicone rubber process cannot improve the ablation resistance and mechanical properties of silicone rubber.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention discloses a method for preparing a phenolic resin modified silicone rubber ablation-resistant coating material, comprising the following steps:

[0008] 1) dissolving 100 parts by mass of silicone rubber in a solvent to obtain a silicone rubber solution;

[0009] 2) adding 5 to 100 parts by mass of a silicone oil-modified phenolic resin, 3 to 8 parts of a vulcanizing agent, 0 to 3 parts of a curing agent, 20 to 40 parts of fumed silica, 4 to 6 parts of chopped carbon fibers, and 4 to 6 parts of chopped aramid fibers to a silicone rubber solution, stirring the mixture thoroughly, drying the mixture to remove the solvent, and kneading the mixture to obtain a phenolic resin-modified silicone rubber raw sheet;

[0010] 3) placing the phenolic resin modified silicone rubber raw film in a mold, heating and vulcanizing it at 150-180° C. and a pressure of 0.5-2 MPa for 20-60 minutes to obtain a phenolic resin modified silicone rubber ablation-resistant coating material.

[0011] Preferably, in step 1), 100 parts of silicone rubber are dissolved in 20 parts of cyclohexane to prepare a silicone rubber solution.

[0012] Preferably, in step 2), the silicone oil-modified phenolic resin is prepared according to the following method:

[0013] 100 parts by mass of acetone or tetrahydrofuran, 100 parts by mass of isocyanate silicone oil and 30 to 50 parts by mass of thermoplastic phenolic resin are sequentially added into a reactor, an inert gas is introduced for protection, and the mixture is refluxed at 70 to 110° C. for 1.5 to 15 hours. After the reaction is completed, the solvent is removed by reduced pressure distillation to obtain a silicone oil-modified phenolic resin.

[0014] Further preferably, the isocyanate silicone oil is prepared according to the following method:

[0015] By weight, 100 parts of hydroxypropyl silicone oil (AC-80, Ark Fogang Chemical Materials Co., Ltd.) and 8-12 parts of diisocyanate are added to a reactor at 30-60°C with 100 parts of acetone or tetrahydrofuran as a solvent. Inert gas is introduced and the reaction is refluxed at 70-110°C for 1.5-15 hours. After the reaction is completed, the solvent is removed by distillation under reduced pressure to obtain isocyanate silicone oil (ISO).

[0016] More preferably, the number average molecular weight of the hydroxypropyl silicone oil is in the range of 3100 to 3600 Da; the diisocyanate is one or a mixture of toluene-2,4-diisocyanate and hexyl diisocyanate; and the molar ratio of the hydroxypropyl silicone oil to the diisocyanate compound is 1:(1.95 to 2.05).

[0017] Further preferably, the thermoplastic phenolic resin has a number average molecular weight range of 500 to 1900 Da; the molar ratio of the isocyanate group in the isocyanate silicone oil to the phenolic hydroxyl group in the thermoplastic phenolic resin is 1:(5.9 to 16.1).

[0018] Preferably, the silicone rubber is methyl vinyl silicone rubber with a number average molecular weight of 490 to 520 kDa; the vulcanizing agent is 2,5-dimethyl-2,5-bishexane or 2,4-dichlorobenzoyl peroxide; and the curing agent is one or more of hexamethylenetetramine, phenylboric acid and boric acid.

[0019] Preferably, the chopped fibers are carbon fibers with a length of 5 to 7 mm (from Inner Mongolia Hexi Aerospace Composite Materials Co., Ltd.), and the chopped aramid fibers are aramid fibers with a length of 5 to 7 mm (from Shanghai Dongfang Technology Co., Ltd.).

[0020] The present invention discloses a phenolic resin modified silicone rubber ablation-resistant coating material prepared by the above-mentioned preparation method. The phenolic resin modified silicone rubber ablation-resistant coating material is a sheet-shaped silicone rubber material with a thickness of 0.1 to 5 mm, a mass ablation rate of 0.0410 g / s, and a linear ablation rate of 0.0605 mm / s.

[0021] The present invention also discloses the application of the phenolic resin modified silicone rubber ablation-resistant coating material in preparing a solid rocket engine insulation layer material.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention discloses a method for preparing a phenolic resin-modified silicone rubber ablation-resistant coating material. The method utilizes a chemical reaction between isocyanate and hydroxyl groups to combine phenolic resin and silicone oil. The silicone oil-modified phenolic resin is more easily and stably dispersed in the silicone rubber. The phenolic resin-modified silicone rubber has a high carbonization rate and excellent mechanical properties. The composite material prepared using the phenolic resin as a matrix has very low mass ablation rate and linear ablation rate, and is expected to be used for internal and external thermal protection of solid rocket engines. The advantages of this method are mainly reflected in:

[0024] 1) Through molecular-level structural design and process optimization, a novel triblock copolymer containing phenolic resin and siloxane groups was synthesized, achieving nanoscale dispersion of the phenolic resin in a silicone rubber system. On the one hand, the siloxane segments in the block copolymer are compatible with silicone rubber, which can act as a compatibilizer in the silicone rubber-phenolic resin blend system. On the other hand, the use of an isocyanate compound for grafting the phenolic resin and silicone rubber facilitates the design of a wide range of modification systems and optimizes the mixing process, resulting in a silicone rubber modified with nanoscale dispersion of phenolic resin.

[0025] 2) By introducing nano-dispersed phenolic resin, the silicone rubber's mass retention at high temperatures is significantly increased, while also significantly improving its mechanical properties. Furthermore, by adding reinforcing fillers such as fumed silica, chopped carbon fibers, and aramid fibers, silicone rubber with a high carbon residue, high strength, and low linear ablation rate is produced, a feat unmatched by many traditional modification methods. Therefore, this invention has the potential to be used as a high-performance ablative coating for solid rocket engines, potentially achieving a significant upgrade in ablative-resistant coating materials for solid rocket engines. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 FTIR spectra of the isocyanate-terminated silicone oil and the phenolic resin-terminated silicone oil described in Example 1, wherein a is hydroxypropyl silicone oil, b is isocyanate-terminated silicone oil, and c is silicone oil-modified phenolic resin;

[0027] Figure 2 1 is the appearance of the phenolic resin modified silicone rubber ablation-resistant coating material described in Example 1 before and after ablation; a is before ablation; b is after ablation. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0029] It should be noted that the terms "first," "second," and the like in the specification and claims of the present invention and the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, so that the embodiments described herein can also be implemented in other orders. In addition, the terms "including," "having," and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or apparatus.

[0030] The present invention is described in further detail below with reference to the accompanying drawings:

[0031] The silicone rubber used in the following embodiments of the present invention is a methyl vinyl silicone rubber with a number average molecular weight of 490 to 520 kDa (MVQ, Shandong Dayi Chemical Co., Ltd.); the chopped fibers are carbon fibers with a length of 5 to 7 mm (Inner Mongolia Hexi Aerospace Composite Materials Co., Ltd.) and aramid fibers with a length of 5 to 7 mm (Shanghai Dongfang Technology Co., Ltd.); the thermoplastic phenolic resin (brand AH-03W, Zhejiang Shitao Dingge New Materials Co., Ltd.) is a thermoplastic phenolic resin with a number average molecular weight range of 500 to 1900 Da; and hydroxypropyl silicone oil (AC-80, Ark Fogang Chemical Materials Co., Ltd.).

[0032] Example 1

[0033] (1) 8 g of toluene-2,4-diisocyanate was dissolved in 100 g of acetone at 30°C, and 100 g of hydroxypropyl silicone oil was added. The mixture was refluxed at 70°C for 1.5 h. The solvent was removed by vacuum drying, and the product was dried to a constant weight to obtain an isocyanate-terminated siloxane.

[0034] (2) Dissolve 30 g of thermoplastic phenolic resin in 100 g of acetone and heat to 45° C.; add 100 g of isocyanate-terminated siloxane and reflux at 70° C. for 15 h to obtain silicone oil-modified phenolic resin;

[0035] (3) 100 g of methyl vinyl silicone rubber was dissolved in 20 g of cyclohexane, and 3 g of 2,5-dimethyl-2,5-bishexane, 5 g of silicone oil-modified phenolic resin, 20 g of fumed silica, 4 g of chopped carbon fiber and 4 g of chopped aramid fiber were added to the methyl vinyl silicone rubber solution and stirred with a glass rod at room temperature. After stirring evenly, the mixture was placed in a vacuum oven to remove the solvent, and then added to a double-roll mill. After mixing evenly, the mixture was sheeted for standby use to obtain a phenolic resin-modified silicone rubber raw sheet;

[0036] (4) The mixed silicone rubber is placed in a program-controlled tablet press, heated and vulcanized at 150° C., a vulcanization time of 20 min, and a pressure of 2 MPa to obtain a phenolic resin modified silicone rubber ablation-resistant coating material.

[0037] The isocyanate-terminated siloxane and silicone oil-modified phenolic resin prepared in this example were subjected to FTIR testing using a TENSOR 27 infrared spectrometer from Bruker, Germany; the scanning range was 400-4000 cm -1 , with a resolution of 4cm -1 The scanning number is 22 times. The transmission method is used for testing. The specific steps are as follows: 10-20 mg of sample and spectrally pure potassium bromide (KBr) are ground evenly in a mortar; the powder is placed in a mold and then pressed into a transparent disc on a tablet press; the disc is placed in the FTIR instrument for testing. The results are as follows Figure 1 As shown, at 1716cm -1 The C=O characteristic peak of the ester group appeared at 2270 cm -1 There is a stretching vibration peak of N=C=O at 2270cm, indicating that the synthesized prepolymer still contains N=C=O groups. -1 The stretching vibration peak of N=C=O at 1716cm -1 The appearance of the stretching vibration peak of the carbonyl group (C=O) in the carbamate is a sign of reaction between the phenolic resin and the isocyanate-terminated silicone oil, indicating that the phenolic hydroxyl group has reacted with the isocyanate group. The isocyanate-terminated siloxanes and silicone oil-modified phenolic resins synthesized in the following examples have infrared spectra essentially the same as those in Example 1 and are not described in detail here.

[0038] The ablation performance of the phenolic resin modified silicone rubber ablation-resistant coating material prepared in this example was tested using a homemade oxyacetylene testing machine. The test specimen was cylindrical, 30 mm in diameter, and 10 mm thick. The volume ratio of oxygen to acetylene was 1.35:1, the nozzle diameter was 2 mm, the distance between the sample surface and the nozzle was 10 ± 0.2 mm, the ablation angle was 90°, and the flame heat flux was 4186.8 ± 418.68 kW / m 2 The results are as follows Figure 2 As shown, it can be seen that after the sample is ablated ( Figure 2 In b), there are obvious ablation pits and white molten droplets are formed on the surface.

[0039] The mechanical properties of the phenolic resin modified silicone rubber ablation-resistant coating material prepared in this example were tested using a SANS6503 universal testing machine from Shenzhen Xinsansi Co., Ltd. The tensile rate was 200 mm / min, and the dimensions of the dumbbell-shaped specimen were 50 mm × 10 mm × 1.5 mm. The results are shown in Table 1. The tensile strength of the prepared phenolic resin modified silicone rubber ablation-resistant coating material can reach 50 times that of the original silicone rubber.

[0040] Example 2

[0041] (1) Dissolve 9 g of toluene-2,4-diisocyanate in 100 g of acetone at 35°C, add 100 g of hydroxypropyl silicone oil, and reflux at 70°C for 15 h. Remove the solvent by vacuum drying, and dry the product to constant weight to obtain isocyanate-terminated siloxane;

[0042] (2) Dissolve 30 g of thermoplastic phenolic resin in 100 g of acetone and heat to 45° C.; add 100 g of isocyanate-terminated siloxane and reflux at 80° C. for 10 h to obtain silicone oil-modified phenolic resin;

[0043] (3) 100 g of methyl vinyl silicone rubber was dissolved in 20 g of cyclohexane, and 3.5 g of 2,5-dimethyl-2,5-bishexane, 10 g of silicone oil-modified phenolic resin, 20 g of fumed silica, 5 g of chopped carbon fiber and 5 g of chopped aramid fiber were added to the methyl vinyl silicone rubber solution and stirred with a glass rod at room temperature. After stirring evenly, the mixture was placed in a vacuum oven to remove the solvent, and then added to a double-roll mill. After mixing evenly, the mixture was sheeted for standby use to obtain a phenolic resin-modified silicone rubber raw sheet;

[0044] (4) The mixed silicone rubber is placed in a program-controlled tablet press, heated and vulcanized at 150° C., a vulcanization time of 20 min, and a pressure of 2 MPa to obtain a phenolic resin modified silicone rubber ablation-resistant coating material.

[0045] Example 3

[0046] (1) Dissolve 10 g of toluene-2,4-diisocyanate in 100 g of acetone at 40°C, add 100 g of hydroxypropyl silicone oil, and reflux at 90°C for 6 h. Remove the solvent by vacuum drying, and dry the product to constant weight to obtain isocyanate-terminated siloxane;

[0047] (2) Dissolve 50 g of thermoplastic phenolic resin in 100 g of acetone and heat to 45° C.; add 100 g of isocyanate-terminated siloxane and reflux at 90° C. for 6 h to obtain silicone oil-modified phenolic resin;

[0048] (3) 100 g of methyl vinyl silicone rubber was dissolved in 20 g of cyclohexane, and 5 g of 2,5-dimethyl-2,5-bishexane, 40 g of silicone oil-modified phenolic resin, 1 g of hexamethylenetetramine, 1 g of boric acid, 40 g of fumed silica, 4.5 g of chopped carbon fiber and 4 g of chopped aramid fiber were added to the methyl vinyl silicone rubber solution and stirred with a glass rod at room temperature. After stirring evenly, the mixture was placed in a vacuum oven to remove the solvent, and then added to a double-roll mill. After mixing evenly, the mixture was sheeted for standby use to obtain a phenolic resin-modified silicone rubber raw sheet;

[0049] (4) The mixed silicone rubber is placed in a program-controlled tablet press, and heated and vulcanized at 165° C., a vulcanization time of 35 min, and a pressure of 1.5 MPa to obtain a phenolic resin modified silicone rubber ablation-resistant coating material.

[0050] Example 4

[0051] (1) Dissolve 11 g of toluene-2,4-diisocyanate in 100 g of acetone at 45°C, add 100 g of hydroxypropyl silicone oil, and reflux at 100°C for 4 h. Remove the solvent by vacuum drying, and dry the product to constant weight to obtain isocyanate-terminated siloxane.

[0052] (2) Dissolve 50 g of thermoplastic phenolic resin in 100 g of acetone and heat to 45° C.; add 100 g of isocyanate-terminated siloxane and reflux at 100° C. for 4 h to obtain silicone oil-modified phenolic resin;

[0053] (3) 100 g of methyl vinyl silicone rubber was dissolved in 20 g of cyclohexane, and 6 g of 2,5-dimethyl-2,5-bishexane, 60 g of silicone oil-modified phenolic resin, 1 g of hexamethylenetetramine, 1 g of phenylboric acid, 1 g of boric acid, 30 g of fumed silica, 4 g of chopped carbon fiber and 6 g of chopped aramid fiber were added to the methyl vinyl silicone rubber solution and stirred with a glass rod at room temperature. After stirring evenly, the mixture was placed in a vacuum oven to remove the solvent, and then added to a double-roll mill. After mixing evenly, the mixture was sheeted for standby use to obtain a phenolic resin-modified silicone rubber raw film;

[0054] (4) The mixed silicone rubber is placed in a program-controlled tablet press, heated and vulcanized at 170°C, a vulcanization time of 30 minutes, and a pressure of 0.8 MPa to obtain a phenolic resin modified silicone rubber ablation-resistant coating material.

[0055] Example 5

[0056] (1) Dissolve 6 g of toluene-2,4-diisocyanate and 6 g of hexyl diisocyanate in 100 g of acetone at 50°C, then add 100 g of hydroxypropyl silicone oil, and reflux at 110°C for 1.5 h. Remove the solvent by vacuum drying, and dry the product to constant weight to obtain isocyanate-terminated siloxane;

[0057] (2) Dissolve 40 g of thermoplastic phenolic resin in 100 g of acetone and heat to 45° C.; add 100 g of isocyanate-terminated siloxane and reflux at 110° C. for 1.5 h to obtain silicone oil-modified phenolic resin;

[0058] (3) 100 g of methyl vinyl silicone rubber was dissolved in 20 g of cyclohexane, and 7 g of 2,5-dimethyl-2,5-bishexane, 80 g of silicone oil-modified phenolic resin, 30 g of fumed silica, 4 g of chopped carbon fiber and 6 g of chopped aramid fiber were added to the methyl vinyl silicone rubber solution and stirred with a glass rod at room temperature. After stirring evenly, the mixture was placed in a vacuum oven to remove the solvent, and then added to a double-roll mill. After mixing evenly, the mixture was discharged and used as a sheet to obtain a phenolic resin-modified silicone rubber raw sheet.

[0059] (4) The mixed silicone rubber is placed in a program-controlled tablet press, heated and vulcanized at 175° C., a vulcanization time of 25 min, and a pressure of 0.6 MPa to obtain a phenolic resin modified silicone rubber ablation-resistant coating material.

[0060] Example 6

[0061] (1) Dissolve 10 g of toluene-2,4-diisocyanate in 100 g of acetone at 55°C, add 100 g of hydroxypropyl silicone oil, and reflux at 90°C for 6 h. Remove the solvent by vacuum drying, and dry the product to constant weight to obtain isocyanate-terminated siloxane;

[0062] (2) Dissolve 40 g of thermoplastic phenolic resin in 100 g of acetone and heat to 45° C.; add 100 g of isocyanate-terminated siloxane and reflux at 90° C. for 6 h to obtain silicone oil-modified phenolic resin;

[0063] (3) 100 g of methyl vinyl silicone rubber was dissolved in 20 g of cyclohexane, and 8 g of 2,5-dimethyl-2,5-bishexane, 100 g of silicone oil-modified phenolic resin, 1 g of phenylboric acid, 1 g of boric acid, 30 g of fumed silica, 5 g of chopped carbon fiber and 5 g of chopped aramid fiber were added to the methyl vinyl silicone rubber solution and stirred with a glass rod at room temperature. After stirring evenly, the mixture was placed in a vacuum oven to remove the solvent, and then added to a double-roll mill. After mixing evenly, the mixture was sheeted for standby use to obtain a phenolic resin-modified silicone rubber raw sheet;

[0064] (4) The mixed silicone rubber is placed in a program-controlled tablet press, heated and vulcanized at 180° C., a vulcanization time of 20 min, and a pressure of 0.5 MPa to obtain a phenolic resin modified silicone rubber ablation-resistant coating material.

[0065] Example 7

[0066] (1) Dissolve 8 g of hexyl diisocyanate in 100 g of acetone at 60°C, add 100 g of hydroxypropyl silicone oil, and reflux at 70°C for 15 h. Remove the solvent by vacuum drying, and dry the product to constant weight to obtain isocyanate-terminated siloxane.

[0067] (2) Dissolve 30 g of thermoplastic phenolic resin in 100 g of acetone and heat to 45° C.; add 100 g of isocyanate-terminated siloxane and reflux at 750° C. for 13 h to obtain silicone oil-modified phenolic resin;

[0068] (3) 100 g of methyl vinyl silicone rubber was dissolved in 20 g of cyclohexane, and 3 g of 2,5-dimethyl-2,5-bishexane, 10 g of silicone oil-modified phenolic resin, 20 g of fumed silica, 4.5 g of chopped carbon fiber and 5.5 g of chopped aramid fiber were added to the methyl vinyl silicone rubber solution and stirred with a glass rod at room temperature. After stirring evenly, the mixture was placed in a vacuum oven to remove the solvent, and then added to a double-roll mill. After mixing evenly, the mixture was sheeted for standby use to obtain a phenolic resin-modified silicone rubber raw sheet;

[0069] (4) The mixed silicone rubber is placed in a program-controlled tablet press, heated and vulcanized at 150° C., a vulcanization time of 60 min, and a pressure of 2 MPa to obtain a phenolic resin modified silicone rubber ablation-resistant coating material.

[0070] Example 8

[0071] (1) Dissolve 9 g of hexyl diisocyanate in 100 g of acetone at 60°C, add 100 g of hydroxypropyl silicone oil, and reflux at 80°C for 10 h. Remove the solvent by vacuum drying, and dry the product to constant weight to obtain isocyanate-terminated siloxane.

[0072] (2) Dissolve 40 g of thermoplastic phenolic resin in 100 g of acetone and heat to 45° C.; add 100 g of isocyanate-terminated siloxane and reflux at 80° C. for 10 h to obtain silicone oil-modified phenolic resin;

[0073] (3) 100 g of methyl vinyl silicone rubber was dissolved in 20 g of cyclohexane, and 4 g of 2,5-dimethyl-2,5-bishexane, 20 g of silicone oil-modified phenolic resin, 1 g of phenylboric acid, 30 g of fumed silica, 5 g of chopped carbon fiber and 5 g of chopped aramid fiber were added to the methyl vinyl silicone rubber solution and stirred with a glass rod at room temperature. After stirring evenly, the mixture was placed in a vacuum oven to remove the solvent, and then added to a double-roll mill. After mixing evenly, the mixture was sheeted for standby use to obtain a phenolic resin-modified silicone rubber raw sheet;

[0074] (4) The mixed silicone rubber is placed in a program-controlled tablet press, heated and vulcanized at 160° C., a vulcanization time of 40 min, and a pressure of 1.5 MPa to obtain a phenolic resin modified silicone rubber ablation-resistant coating material.

[0075] Example 9

[0076] (1) Dissolve 5 g of hexyl diisocyanate and 5 g of toluene-2,4-diisocyanate in 100 g of acetone at 60°C, add 100 g of hydroxypropyl silicone oil, and reflux at 90°C for 6 h. Remove the solvent by vacuum drying, and dry the product to constant weight to obtain isocyanate-terminated siloxane;

[0077] (2) Dissolve 50 g of thermoplastic phenolic resin in 100 g of acetone and heat to 45° C.; add 100 g of isocyanate-terminated siloxane and reflux at 90° C. for 6 h to obtain silicone oil-modified phenolic resin;

[0078] (3) 100 g of methyl vinyl silicone rubber was dissolved in 20 g of cyclohexane, and 5 g of 2,5-dimethyl-2,5-bishexane, 40 g of silicone oil-modified phenolic resin, 0.5 g of hexamethylenetetramine, 1.5 g of phenylboric acid, 40 g of fumed silica, 4 g of chopped carbon fiber and 6 g of chopped aramid fiber were added to the methyl vinyl silicone rubber solution and stirred with a glass rod at room temperature. After stirring evenly, the mixture was placed in a vacuum oven to remove the solvent, and then added to a double-roll mill. After mixing evenly, the mixture was discharged and used as a sheet to obtain a phenolic resin-modified silicone rubber raw sheet;

[0079] (4) The mixed silicone rubber is placed in a program-controlled tablet press, heated and vulcanized at 165° C., a vulcanization time of 35 min, and a pressure of 1 MPa to obtain a phenolic resin modified silicone rubber ablation-resistant coating material.

[0080] Example 10

[0081] (1) Dissolve 11 g of hexyl diisocyanate in 100 g of acetone at 60°C, add 100 g of hydroxypropyl silicone oil, and reflux at 90°C for 6 h. Remove the solvent by vacuum drying, and dry the product to constant weight to obtain isocyanate-terminated siloxane.

[0082] (2) Dissolve 40 g of thermoplastic phenolic resin in 100 g of acetone and heat to 45° C.; add 100 g of isocyanate-terminated siloxane and reflux at 100° C. for 4 h to obtain silicone oil-modified phenolic resin;

[0083] (3) 100 g of methyl vinyl silicone rubber was dissolved in 20 g of cyclohexane, and 6 g of 2,5-dimethyl-2,5-bishexane, 60 g of silicone oil-modified phenolic resin, 2 g of hexamethylenetetramine, 1 g of boric acid, 30 g of fumed silica, 5.5 g of chopped carbon fiber and 4 g of chopped aramid fiber were added to the methyl vinyl silicone rubber solution and stirred with a glass rod at room temperature. After stirring evenly, the mixture was placed in a vacuum oven to remove the solvent, and then added to a double-roll mill. After mixing evenly, the mixture was discharged and used as a sheet to obtain a phenolic resin-modified silicone rubber raw sheet.

[0084] (4) The mixed silicone rubber is placed in a program-controlled tablet press, heated and vulcanized at 170°C, a vulcanization time of 30 minutes, and a pressure of 0.8 MPa to obtain a phenolic resin modified silicone rubber ablation-resistant coating material.

[0085] Example 11

[0086] (1) Dissolve 12 g of hexyl diisocyanate in 100 g of acetone at 60°C, add 100 g of hydroxypropyl silicone oil, and reflux at 110°C for 1.5 h. Remove the solvent by vacuum drying, and dry the product to constant weight to obtain isocyanate-terminated siloxane.

[0087] (2) Dissolve 40 g of thermoplastic phenolic resin in 100 g of acetone and heat to 45° C.; add 100 g of isocyanate-terminated siloxane and reflux at 110° C. for 1.5 h to obtain silicone oil-modified phenolic resin;

[0088] (3) 100 g of methyl vinyl silicone rubber was dissolved in 20 g of cyclohexane, and 7 g of 2,5-dimethyl-2,5-bishexane, 80 g of silicone oil-modified phenolic resin, 30 g of fumed silica, 6 g of chopped carbon fiber and 4 g of chopped aramid fiber were added to the methyl vinyl silicone rubber solution and stirred with a glass rod at room temperature. After stirring evenly, the mixture was placed in a vacuum oven to remove the solvent, and then added to a double-roll mill. After mixing evenly, the mixture was sheeted for standby use to obtain a phenolic resin-modified silicone rubber raw sheet;

[0089] (4) The mixed silicone rubber is placed in a program-controlled tablet press, heated and vulcanized at 175° C., a vulcanization time of 25 min, and a pressure of 0.6 MPa to obtain a phenolic resin modified silicone rubber ablation-resistant coating material.

[0090] Example 12

[0091] (1) Dissolve 10 g of hexyl diisocyanate in 100 g of acetone at 60°C, add 100 g of hydroxypropyl silicone oil, and reflux at 90°C for 6 h. Remove the solvent by vacuum drying, and dry the product to constant weight to obtain isocyanate-terminated siloxane.

[0092] (2) Dissolve 40 g of thermoplastic phenolic resin in 100 g of acetone and heat to 45° C.; add 100 g of isocyanate-terminated siloxane and reflux at 90° C. for 6 h to obtain silicone oil-modified phenolic resin;

[0093] (3) 100 g of methyl vinyl silicone rubber was dissolved in 20 g of cyclohexane, and 8 g of 2,5-dimethyl-2,5-bishexane, 100 g of silicone oil-modified phenolic resin, 2 g of boric acid, 30 g of fumed silica, 5.5 g of chopped carbon fiber and 4.5 g of chopped aramid fiber were added to the methyl vinyl silicone rubber solution and stirred with a glass rod at room temperature. After stirring evenly, the mixture was placed in a vacuum oven to remove the solvent, and then added to a double-roll mill. After mixing evenly, the mixture was discharged and used as a sheet to obtain a phenolic resin-modified silicone rubber raw sheet;

[0094] The mixed silicone rubber was placed in a program-controlled tablet press, and heated and vulcanized at 180° C., a vulcanization time of 20 min, and a pressure of 0.5 MPa to obtain a phenolic resin modified silicone rubber ablation-resistant coating material.

[0095] Table 1. Mechanical properties of phenolic resin modified silicone rubber ablation-resistant coating materials synthesized in various embodiments of the present invention

[0096]

[0097]

[0098] It can be seen that the technology of the present invention is highly feasible, and the obtained silicone rubber has excellent mechanical properties.

[0099] Table 2. Ablation performance parameters of phenolic resin modified silicone rubber ablation-resistant coating materials synthesized in various embodiments of the present invention

[0100]

[0101] Table 2 shows the ablation performance of the phenolic resin modified silicone rubber ablation-resistant coating material prepared based on the present invention. It can be seen that the composite material samples with different filler ratios all show excellent ablation performance.

[0102] The above content is only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a phenolic resin modified silicone rubber ablation-resistant coating material, characterized in that: The following steps are involved: 1) Dissolving 100 parts by mass of silicone rubber in a solvent to obtain a silicone rubber solution; 2) adding 5-100 parts by mass of a silicone oil-modified phenolic resin, 3-8 parts by mass of a vulcanizing agent, 0-3 parts by mass of a curing agent, 20-40 parts by mass of fumed silica, 4-6 parts by mass of chopped carbon fibers, and 4-6 parts by mass of chopped aramid fibers to a silicone rubber solution, stirring the mixture thoroughly, drying the mixture to remove the solvent, and kneading the mixture to obtain a phenolic resin-modified silicone rubber raw sheet; The silicone oil-modified phenolic resin is prepared according to the following method: Mix 100 parts by mass of acetone or tetrahydrofuran, 100 parts by mass of isocyanate silicone oil, and 30-50 parts by mass of thermoplastic phenolic resin, and reflux them at 70-110°C in an inert atmosphere for 1.5-15 hours. After the reaction is complete, remove the solvent to obtain a silicone oil-modified phenolic resin. Wherein, the isocyanate silicone oil is prepared according to the following method: In parts by mass, 100 parts of acetone or tetrahydrofuran, 100 parts of hydroxypropyl silicone oil, and 8 to 12 parts of a diisocyanate compound are mixed at 30 to 60° C., and refluxed at 70 to 110° C. under an inert atmosphere for 1.5 to 15 hours. After the reaction, the solvent is removed to prepare an isocyanate-based silicone oil; the number average molecular weight of the hydroxypropyl silicone oil is in the range of 3100 to 3600 Da; the diisocyanate is one or a mixture of toluene-2,4-diisocyanate and hexyl diisocyanate; the molar ratio of the hydroxypropyl silicone oil to the diisocyanate compound is 1:(1.95 to 2.05); 3) The phenolic resin modified silicone rubber raw film is heated and vulcanized at 150-180° C. and a pressure of 0.5-2 MPa for 20-60 min to prepare a phenolic resin modified silicone rubber ablation-resistant coating material.

2. The method for preparing the phenolic resin modified silicone rubber ablation-resistant coating material according to claim 1, characterized in that: In step 1), 100 parts of silicone rubber are dissolved in 20 parts of cyclohexane to prepare a silicone rubber solution.

3. The method for preparing the phenolic resin modified silicone rubber ablation-resistant coating material according to claim 1, wherein: The thermoplastic phenolic resin has a number average molecular weight ranging from 500 to 1900 Da; the molar ratio of the isocyanate group in the isocyanate silicone oil to the phenolic hydroxyl group in the thermoplastic phenolic resin is 1:(5.9-16.1).

4. The method for preparing the phenolic resin modified silicone rubber ablation-resistant coating material according to claim 1, wherein: The silicone rubber is methyl vinyl silicone rubber with a number average molecular weight of 490-520 kDa; the vulcanizing agent is 2,5-dimethyl-2,5-bishexane or 2,4-dichlorobenzoyl peroxide; and the curing agent is one or more of hexamethylenetetramine, phenylboric acid, and boric acid.

5. The method for preparing the phenolic resin modified silicone rubber ablation-resistant coating material according to claim 1, wherein: The chopped fibers are carbon fibers with a length of 5 to 7 mm, and the chopped aramid fibers are aramid fibers with a length of 5 to 7 mm.

6. A phenolic resin modified silicone rubber ablation-resistant coating material prepared by the preparation method according to any one of claims 1 to 5, characterized in that: The phenolic resin modified silicone rubber ablation-resistant coating material is a sheet of silicone rubber material with a thickness of 0.1 to 5 mm. Its mass ablation rate reaches 0.0410 g / s and its linear ablation rate reaches 0.0605 mm / s.

7. Use of the phenolic resin modified silicone rubber ablation-resistant coating material according to claim 6 in preparing a solid rocket engine insulation layer material.

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