Composition for spraying and preparation process thereof

Abstract

The invention relates to the technical field of thermal spraying coatings, and particularly discloses a composition for spraying and a preparation process thereof. The composition for spraying is prepared from the following raw materials in parts by mass: 80-85 parts of polyether-ether-ketone powder, 5-8 parts of surface activated silicon carbide powder, 5-7 parts of modified phenyl siloxane rubber, 0.5-1 part of an antioxidant and 0.3-0.5 part of fumed silica; the modified phenyl siloxane rubber is obtained by mixing and treating fluorine-carbonized nano silicon dioxide and a phenyl siloxane rubber monomer, and the porosity of a coating obtained by thermal spraying of the composition for spraying obtained by adopting the scheme of the invention is less than 2.5%, the friction coefficient is less than 0.34, and the specific wear rate is less than 9.1 * 10 <-6 > mm < 3 > / (N.m).

Description

Technical Field

[0001] This application relates to the technical field of thermal spray coatings. More specifically, it relates to a composition for spraying and its preparation process. Background Art

[0002] Thermal spraying is a surface processing method in which a spraying material is heated to a molten or semi-molten state by a heat source (such as a plasma arc, flame, electric arc, etc.), and then the molten material is sprayed onto the surface of a substrate through a high-speed gas flow to form a coating. It can significantly improve the surface properties of materials and extend the service life of components. Therefore, it plays a key role in many fields. Commonly used thermal spray materials include metals and alloys, ceramics, polymer materials, etc. Among polymer materials, polyetheretherketone has significant advantages due to its excellent high-temperature resistance, mechanical strength, chemical corrosion resistance, and electrical insulation properties.

[0003] The specific preparation process of the polyetheretherketone coating is that under thermo-mechanical action, the melted polyetheretherketone is accelerated by the high-speed gas flow generated by the heat source. After hitting the surface of the pretreated substrate, it spreads rapidly and cools and solidifies, finally obtaining the coating. Although this coating preparation process is simple and the formed polyetheretherketone coating can firmly adhere to the substrate, the splashing of the melted polyetheretherketone easily causes an increase in the porosity of the obtained polyetheretherketone coating.

[0004] During the spraying process, there is a temperature difference between the substrate and the melted polyetheretherketone. The semi-crystalline polyetheretherketone spreads only for a very short time and then rapidly cools to form microparticles. The stacking and incomplete contact of the particles lead to a significant increase in the pores of the coating film. To solve the pore problem of polyetheretherketone thermal spraying, in addition to preheating the substrate, the currently commonly used solution is to apply a low-viscosity coating to the substrate after the polyetheretherketone coating cools. By means of the penetration of the low-viscosity coating into the polyetheretherketone coating, the purpose of reducing pores is achieved. However, this treatment method easily causes an increase in the coating thickness problem, and after the applied low-viscosity coating solidifies, a small part remains on the outermost layer of the substrate, hindering the inner polyetheretherketone coating from exerting its effect.

[0005] Chinese patent application document with the application publication number CN104789086A discloses a high-temperature resistant thermal spray sealant and its usage method. In the application solution, resin, filler, curing agent, metal powder, etc. are mixed to prepare the sealant. This sealant has good permeability and stability. After brushing, it can block the pores of the coating through the penetration effect, and the obtained coating has significantly enhanced anti-wear and anti-corrosion capabilities.

[0006] In the above application solution, the provided thermal spraying sealant and its usage method, although to a certain extent solve the problem of the increasing porosity of polyetheretherketone thermal spraying, the solution still requires secondary brushing treatment, and the operation is too cumbersome; therefore, it is necessary to find a spraying composition and its preparation process that can improve the porosity problem of polyetheretherketone thermal spraying while simplifying the film-forming process. Summary of the Invention

[0007] In order to further reduce the problem of excessive porosity of the polyetheretherketone coating obtained by thermal spraying and simplify the film-forming process at the same time, the present application provides a spraying composition and its preparation process.

[0008] In the first aspect, the present application provides a preparation process of a spraying composition, which is made from raw materials including the following parts by mass: 80 - 85 parts of polyetheretherketone powder, 5 - 8 parts of surface-activated silicon carbide powder, 5 - 7 parts of modified phenyl silicone rubber, 0.5 - 1 part of antioxidant, and 0.3 - 0.5 part of fumed silica; it includes the following steps: Take the surface-activated silicon carbide powder, and mix it with the polyetheretherketone powder, modified phenyl silicone rubber, antioxidant, and fumed silica at high speed to obtain it; Among them, the preparation of the modified phenyl silicone rubber includes the following steps: (1) Take nano-silica, add an activator, disperse it in a mixed solvent, then heat it up and stir overnight, add fluorinated organosilane, then continue to heat it up for treatment, cool it down and centrifuge, take the precipitate, wash it, and dry it to obtain fluorinated carbonized nano-silica; (2) Take hexamethylcyclotrisiloxane and diphenylsilane, dehydrate and mix them for dispersion, add potassium trimethylsilanolate and the activated fluorinated carbonized nano-silica dispersion, react at a gradient temperature, then cool it down, add an oligomerization agent, carry out constant-temperature reflux treatment, then add triphenylphosphine for further treatment, finally add hexamethyldisiloxane for end-capping, stir at high speed, evacuate to evaporate the solvent, wash with alcohol and dry to obtain the modified phenyl silicone rubber.

[0009] By adopting the above technical solutions, the compatibility between the components of the composition for spraying can be improved, and the pore level of the coating after thermal spraying can be improved by the difference in the crystallization properties between the components of the composition. In the modified phenyl silicone rubber, the activated fluorinated carbonized nano-silica serves as the central nucleon, and hexamethylcyclotrisiloxane and diphenylsilane serve as the bonding monomers, and a composite structure is obtained through the condensation of silicon hydroxyl groups. After the nano-silica is modified by fluorinated carbonization, its surface energy can be reduced, making it easier for the polymerization reaction of the phenyl silicone rubber condensation monomers to occur on the nano-silica; at the same time, the introduction of strong polar fluorocarbon bonds also improves the compatibility between the modified phenyl silicone rubber and polyetheretherketone during the thermal spraying process, avoiding stress concentration and uneven dispersion during the condensation of the two-component coating. The low-molecular-weight phenyl silicone rubber obtained through the polymerization reaction is affected by the central fluorinated carbonized nano-silica nucleon, and a local regular structure is formed near the nucleus. The formation of this local regular structure can promote the interpenetration of molecular chains between the modified phenyl silicone rubber and the semi-crystalline polymer polyetheretherketone during the cooling process after spraying. The composite crystal property is between semi-crystalline and amorphous. Due to the increase in the degree of disorder of the chain segments, the crystallization behavior of polyetheretherketone in the composition is inhibited, and the coating has a more sufficient spreading time, ultimately achieving the effect of reducing pores.

[0010] Preferably, the preparation of the surface-activated silicon carbide powder includes the following steps: Take silicon carbide powder, after alcohol washing and drying, place it in a silane coupling agent dispersion solution for ultrasonic treatment at 60 - 65 °C for 3 - 4 h, then filter to obtain the precipitate, and obtain it after alcohol washing and drying; the silane coupling agent dispersion solution is obtained by mixing γ-aminopropyltriethoxysilane and deionized water in a mass ratio of (50 - 100):1.

[0011] By adopting the above technical solutions, through the treatment with silane coupling agents, the mixing effect of silicon carbide powder and polyetheretherketone in the melt can be improved, and the coating quality can be improved.

[0012] Preferably, in the step (1), the activator is one of quinic acid, salicylic acid, L-ascorbic acid, and citric acid; The mass ratio of the nano-silica, activator, and fluorinated organosilane used is 7.5:(0.2 - 0.5):(0.5 - 0.8); The fluorinated organosilane is one of trifluoropropylmethyl silicone oil, (trifluoromethyl)trimethylsilane, and tridecafluorooctyltrimethoxysilane; The mixed solvent is obtained by mixing deionized water and propylene glycol in a volume ratio of (1.5 - 2):1.

[0013] By adopting the above technical solution, treating nano-silica with plant-derived organic acid gently can improve the reaction activity of nano-silica and fluorinated organosilane. The carboxyl group in the acid reacts with the silicon-oxygen bond on the surface of silica, resulting in more reactive silicon hydroxyl groups (Si-OH) on the surface of nano-silica, which can increase the density of silicon hydroxyl groups on nano-silica and is beneficial to the subsequent reaction.

[0014] By adopting the above technical solution, the fluorinated carbon nano-silica obtained with the above raw materials and ratio has the best effect.

[0015] Preferably, in the step (2), the mass ratio of hexamethylcyclotrisiloxane to diphenylsilane raw materials is (52.5 - 55.6):(15.2 - 16.5).

[0016] By adopting the above technical solution, adjusting the raw material ratio of hexamethylcyclotrisiloxane to diphenylsilane and controlling the subsequent oligomerization process can obtain medium-phenyl silicone rubber with a moderate benzene content. Due to the introduction of multi-phenyl functional groups, the silicone rubber has a larger steric hindrance. The presence of phenyl can inhibit the attack of oxidizing radicals on the silicone rubber chain segment and prevent a large amount of oxidative decomposition. At the same time, the dense benzene ring rigid structure increases the energy barrier required for the thermal decomposition of medium-phenyl silicone rubber, making the molecule less likely to decompose at high temperatures.

[0017] Preferably, in the step (2), the activated fluorinated carbon nano-silica dispersion is obtained by mixing fluorinated carbon nano-silica, activator, polyvinylpyrrolidone, and sodium polyacrylate according to a mass ratio of (5.2 - 5.5):(0.1 - 0.2):(0.5 - 0.7):(0.2 - 0.3), and then treating at 50 - 60 °C for 0.5 - 1 h.

[0018] By adopting the above technical solution, using the raw materials with the above ratio can further activate the fluorinated carbon nano-silica and play a better nucleation effect in the subsequent preparation process of medium-phenyl silicone rubber.

[0019] Preferably, in the step (2), the specific operation of gradient heating is to raise the system temperature to 105 - 110 °C at a rate of 3.7 - 4.5 °C / min.

[0020] By adopting the above technical solution, a reaction environment can be provided here for the ring-opening of hexamethylcyclotrisiloxane and the prenucleation of fluorinated carbonized nano-silica. Potassium trimethylsilanolate, an anionic basic ring-opening agent, as a nucleophile, can attack the silicon atom in the cyclic silane and cause the silicon-oxygen bond to break, obtaining a reactive linear hexamethylsilane intermediate structure; under the subsequent catalysis of a nickel-based oligomerization agent, the intermediate reacts with diphenylsilane to undergo a silane polymerization reaction to obtain a medium phenylsilane segment; after activation treatment, the fluorinated carbonized nano-silica has a lower reaction energy barrier on the surface, and the initially formed medium phenylsilane segment is more likely to form a graft structure on the fluorinated carbonized nano-silica. Adjusting the gradient heating can more gently promote the reaction to proceed.

[0021] Preferably, in the step (2), the oligomerization agent is nickel acetylacetonate; the constant-temperature reflux treatment time is 35 - 40 min.

[0022] By adopting the above technical solution, using nickel acetylacetonate with a low polymerization catalytic effect can regulate the polymerization process of medium phenyl silicone rubber. By regulating the constant-temperature reflux time, the situation of too fast polymerization of raw materials can be avoided; the subsequent added triphenylphosphine can chelate with nickel acetylacetonate to prevent the continuous progress of the catalytic polymerization reaction. In combination with the end-capping agent hexamethyldisiloxane, the termination of the catalytic polymerization reaction can be finally achieved.

[0023] Preferably, in the step (2), the high-speed stirring controls the stirring speed at 1000 - 2000 rpm and is carried out for 10 - 30 min.

[0024] By adopting the above technical solution, through sufficient dispersion by high-speed stirring, the agglomeration behavior of the modified phenyl silicone rubber can be inhibited, and the obtained modified phenyl silicone rubber has a better mixing effect with each composition raw material component for spraying.

[0025] In the second aspect, the composition for spraying is prepared by the above preparation process in this application.

[0026] In summary, this application has the following beneficial effects: 1. This application uses fluorinated and carbonized modified nano-silica as the central nucleus, and through the combined reaction with phenyl silicone rubber synthesis monomers, a modified phenyl silicone rubber is prepared. After fluorinated and carbonized modification, the nano-silica has a lower surface energy, which can make it easier for phenyl silicone rubber synthesis monomers to condense through silanol groups on it to obtain a composite structure; during the silanol group condensation reaction, the polymer chain segments around the fluorinated and carbonized nano-silica of the modified phenyl silicone rubber are arranged orderly under the action of the central nucleus. The formation of this local regular structure can promote the interpenetration of molecular chains between the modified phenyl silicone rubber and the semi-crystalline polymer polyether ether ketone during the cooling process after spraying, forming a structure of an organic polymer between semi-crystalline and amorphous, thereby inhibiting the rapid crystallization behavior of polyether ether ketone in the composition, enabling the coating to spread more fully, and ultimately achieving the effect of reducing pores.

[0027] 2. The composition for thermal spraying obtained by the solution of this application has a porosity of the thermally sprayed coating < 2.5%, a friction coefficient < 0.34, and a specific wear rate < 9.1×10 -6 mm 3 / (N·m). Description of the Drawings

[0028] Figure 1 This is the SEM image of the coating obtained by thermal spraying of the test sample of the composition for thermal spraying in Example 2 and Comparative Example 1 of this application.

[0029] Figure 2 This is the porosity of the coating obtained by thermal spraying of the test sample of the composition for thermal spraying in Examples 1-5 and Comparative Examples 1-2 of this application.

[0030] Figure 3 This is the friction coefficient and specific wear rate of the coating obtained by thermal spraying of the test sample of the composition for thermal spraying in Examples 1-5 and Comparative Examples 1-2 of this application. Detailed Description of the Invention

[0031] Example 1 In this example, the composition for thermal spraying is made of the following raw materials by weight: 80 g of polyether ether ketone powder, 5 g of modified phenyl silicone rubber, 0.5 g of tris(2,4-di-tert-butylphenyl) phosphite, 5 g of surface-activated silicon carbide powder, and 0.3 g of fumed silica; the specific steps are as follows: Take the surface-activated silicon carbide powder, mix it with the polyether ether ketone powder, modified phenyl silicone rubber, tris(2,4-di-tert-butylphenyl) phosphite, and fumed silica, adjust the mixing rotation speed to 500 rpm and process for 2 min, then increase the rotation speed to 2000 rpm and process for 10 min to obtain the composition for thermal spraying.

[0032] In this example, the preparation steps of the modified phenyl silicone rubber are specifically as follows: (1) Take a 250 ml three-necked flask, add 100 ml of the mixed solvent, then add 7.5 g of nano-silica and 0.2 g of quinic acid. Raise the temperature of the system to 40 °C and stir overnight. Then add 0.5 g of trifluoropropyl methyl silicone oil and stir at 150 rpm for 6 h. Subsequently, raise the temperature of the system to 70 °C and carry out a condensation reflux reaction for 2 h. After that, cool to room temperature, centrifuge at 7000 rpm for 10 min, take the precipitate, wash it twice with absolute ethanol at 40 °C, and then wash it three times with toluene. Dry it at 45 °C to obtain fluorinated carbonized nano-silica.

[0033] (2) Take 52.5 g of hexamethylcyclotrisiloxane and 15.2 g of diphenylsilane respectively, stir and heat at 45 °C for 3 h. After mixing under a nitrogen atmosphere, place it in 300 ml of toluene, adjust the magnetic stirring speed to 150 rpm, and disperse for 5 min. Then add 0.5 g of potassium trimethylsilanolate and 5.8 g of the activated fluorinated carbonized nano-silica dispersion. Subsequently, raise the temperature of the system to 105 °C at a rate of 3.7 °C / min and stir for 2 h. After that, stop heating. When the temperature drops to 65 °C, add 0.2 g of nickel acetylacetonate, carry out a constant temperature reflux treatment for 35 min, immediately add 0.23 g of triphenylphosphine, increase the stirring speed to 300 rpm, and treat for 5 min. Then add 2.2 g of hexamethyldisiloxane and continue to treat for 0.5 h. Then transfer the mixture to a closed reaction kettle and treat it at a high magnetic stirring speed of 1000 rpm for 10 min. After that, adjust the vacuum degree to -0.1 MPa and adjust the temperature to 65 °C and treat for 2 h. Finally, wash it three times with absolute ethanol and dry it to obtain modified phenyl silicone rubber.

[0034] In this example, the preparation steps of the surface-activated silicon carbide powder are as follows: Take 4.5 g of silicon carbide powder, wash and dry it with absolute ethanol, place it in 50 ml of the silane coupling agent dispersion, adjust the temperature to 60 °C, and carry out ultrasonic treatment at 22.5 kHz for 3 h. Finally, filter to obtain the precipitate, and wash and dry it again with absolute ethanol.

[0035] In this example, the preparation steps of the activated fluorinated carbonized nano-silica dispersion are as follows: Take 5.2 g of fluorinated carbonized nano-silica, mix it with 0.1 g of quinic acid, 0.5 g of polyvinylpyrrolidone, and 0.2 g of sodium polyacrylate, adjust the magnetic stirring speed to 100 rpm, adjust the temperature to 50 °C, and treat for 0.5 h to obtain it.

[0036] Among them, the polyetheretherketone powder (average particle size 25 μm) was provided by Shunbang New Materials Factory in Zhangqiu District, Jinan City. The silicon carbide powder (average particle size 10 μm) was provided by Forsman Technology (Beijing) Co., Ltd. The fumed silica (average particle size 12 nm) was provided by Guangzhou Jingyi New Materials Co., Ltd. The silane coupling agent dispersion was obtained by mixing γ-aminopropyltriethoxysilane and deionized water in a mass ratio of 50:1. The mixed solvent was obtained by mixing deionized water and propylene glycol in a volume ratio of 1.5:1.

[0037] Example 2 In this example, the composition for spraying was made from the following raw materials by weight: 82 g of polyetheretherketone powder, 6 g of modified phenyl silicone rubber, 0.75 g of tris(2,4-di-tert-butylphenyl) phosphite, 7 g of surface-activated silicon carbide powder, and 0.3 g of fumed silica; the specific steps are as follows: Take the surface-activated silicon carbide powder, mix it with the polyetheretherketone powder, modified phenyl silicone rubber, tris(2,4-di-tert-butylphenyl) phosphite, and fumed silica, adjust the mixing speed to 500 rpm and process for 2 min, then increase the speed to 2000 rpm and process for 10 min to obtain the composition for spraying.

[0038] In this example, the preparation steps of the modified phenyl silicone rubber are specifically as follows: (1) Take a 250 ml three-necked flask, add 100 ml of the mixed solvent, then add 7.5 g of nano-silica and 0.3 g of salicylic acid, raise the system temperature to 45 °C and stir overnight, then add 0.8 g of (trifluoromethyl)trimethylsilane, stir at 175 rpm for 6 h, then raise the system temperature to 80 °C for condensation reflux reaction for 2 h, then cool to room temperature, centrifuge at 7500 rpm for 10 min, take the precipitate, wash it twice with anhydrous ethanol at 40 °C, and then wash it three times with toluene, and dry it at 45 °C to obtain fluorinated carbonized nano-silica.

[0039] (2)Take 53 g of hexamethylcyclotrisiloxane and 15.7 g of diphenylsilane respectively, stir and heat at 45 °C for 3 h. After mixing under a nitrogen atmosphere, place it in 300 ml of toluene, adjust the magnetic stirring speed to 150 rpm, disperse for 10 min, then add 0.5 g of potassium trimethylsilanolate and 6.2 g of activated fluorinated carbonized nano-silica dispersion. Subsequently, raise the system temperature to 105 °C at a rate of 4 °C / min, stir and react for 2 h. Then stop heating. When the temperature drops to 68 °C, add 0.22 g of nickel acetylacetonate, carry out constant temperature reflux treatment for 35 min, immediately add 0.27 g of triphenylphosphine, increase the stirring speed to 300 rpm, treat for 15 min, then add 2.4 g of hexamethyldisiloxane, continue to treat for 0.5 h, then transfer the mixture to a closed reaction kettle, under a high magnetic stirring speed of 1500 rpm, treat for 25 min, then adjust the vacuum degree to -0.1 MPa, adjust the temperature to 65 °C, treat for 2 h, and finally wash three times with absolute ethanol, and obtain modified phenyl silicone rubber after drying.

[0040] In this example, the preparation steps of the surface-activated silicon carbide powder are specifically as follows: Take 4.7 g of silicon carbide powder, after washing and drying with absolute ethanol, place it in 50 ml of silane coupling agent dispersion, adjust the temperature to 60 °C, carry out ultrasonic treatment at 22.5 kHz for 3 h, and finally filter to obtain the precipitate, and obtain it again after washing and drying with absolute ethanol.

[0041] In this example, the preparation steps of the activated fluorinated carbonized nano-silica dispersion are specifically as follows: Take 5.3 g of fluorinated carbonized nano-silica, mix it with 0.1 g of salicylic acid, 0.5 g of polyvinylpyrrolidone, and 0.2 g of sodium polyacrylate, then adjust the magnetic stirring speed to 120 rpm, adjust the temperature to 55 °C, and obtain it after treating for 1 h.

[0042] Among them, the polyetheretherketone powder (average particle size 25 microns) is provided by Shunbang New Materials Factory in Zhangqiu District, Jinan City. The silicon carbide powder (average particle size 10 microns) is provided by Forsman Technology (Beijing) Co., Ltd. The fumed silica (average particle size 12 nm) is provided by Guangzhou Jingyi New Materials Co., Ltd. The silane coupling agent dispersion is obtained by mixing γ-aminopropyltriethoxysilane and deionized water in a mass ratio of 75:1. The mixed solvent is obtained by mixing deionized water and propylene glycol in a volume ratio of 1.5:1.

[0043] Example 3 In this example, the composition for spraying is made of the following raw materials by weight: 85 g of polyetheretherketone powder, 7 g of modified phenyl silicone rubber, 1 g of tris(2,4-di-tert-butylphenyl) phosphite, 8 g of surface-activated silicon carbide powder, 0.5 g of fumed silica; the specific steps are as follows: Take surface-activated silicon carbide powder, mix it with polyetheretherketone powder, modified phenyl silicone rubber, tris(2,4-di-tert-butylphenyl) phosphite, and fumed silica. Adjust the mixing speed to 1000 rpm and process for 3 min, then increase the speed to 3000 rpm and process for 15 min to obtain the composition for spraying.

[0044] In this example, the preparation steps of the modified phenyl silicone rubber are as follows: (1) Take a 250 ml three-necked flask, add 100 ml of mixed solvent, then add 7.5 g of nano-silica and 0.5 g of L-ascorbic acid. Raise the system temperature to 50 °C and stir overnight. Then add 0.8 g of trifluorooctyltrimethoxysilane, stir at 200 rpm for 6 h, then raise the system temperature to 85 °C and carry out condensation reflux reaction for 2 h. After that, cool to room temperature, centrifuge at 9000 rpm for 30 min, take the precipitate, wash it twice with absolute ethanol at 40 °C, and then wash it three times with toluene, and dry it at 50 °C to obtain fluorinated carbonized nano-silica.

[0045] (2) Take 55.6 g of hexamethylcyclotrisiloxane and 16.5 g of diphenylsilane respectively, stir and heat at 50 °C for 4 h, then mix them under a nitrogen atmosphere, place them in 350 ml of toluene, adjust the magnetic stirring speed to 150 rpm, disperse for 20 min, then add 0.6 g of potassium trimethylsilanolate, and 6.5 g of activated fluorinated carbonized nano-silica dispersion. Subsequently, raise the system temperature to 110 °C at a rate of 4.5 °C / min and stir and react for 2.5 h. Then stop heating. When the temperature drops to 70 °C, add 0.35 g of nickel acetylacetonate, carry out constant temperature reflux treatment for 40 min, immediately add 0.27 g of triphenylphosphine, increase the stirring speed to 350 rpm, process for 20 min, then add 2.5 g of hexamethyldisiloxane, continue to process for 1 h, then transfer the mixture to a closed reaction kettle, process at a high magnetic stirring speed of 2000 rpm for 30 min, then adjust the vacuum degree to -0.1 MPa, adjust the temperature to 65 °C, process for 2 h, and finally wash it three times with absolute ethanol and dry it to obtain the modified phenyl silicone rubber.

[0046] In this example, the preparation steps of the surface-activated silicon carbide powder are as follows: Take 4.8 g of silicon carbide powder, wash and dry it with absolute ethanol, then place it in 50 ml of silane coupling agent dispersion, adjust the temperature to 65 °C, and carry out ultrasonic treatment at 22.5 kHz for 4 h. Finally, filter to obtain the precipitate, and wash and dry it again with absolute ethanol.

[0047] In this example, the preparation steps of the activated fluorinated carbonized nano-silica dispersion are as follows: 5.5 g of fluorinated carbonized nano-silica is taken, mixed with 0.2 g of L-ascorbic acid, 0.7 g of polyvinylpyrrolidone, and 0.3 g of sodium polyacrylate, then the magnetic stirring speed is adjusted to 120 rpm, the temperature is adjusted to 60 °C, and it is obtained after treatment for 1 h.

[0048] Among them, the polyetheretherketone powder (average particle size 25 μm) is provided by Shunbang New Materials Factory in Zhangqiu District, Jinan City. The silicon carbide powder (average particle size 10 μm) is provided by Forsman Technology (Beijing) Co., Ltd. The fumed silica (average particle size 12 nm) is provided by Guangzhou Jingyi New Materials Co., Ltd. The silane coupling agent dispersion is obtained by mixing γ-aminopropyltriethoxysilane and deionized water in a mass ratio of 100:1. The mixed solvent is obtained by mixing deionized water and propylene glycol in a volume ratio of 2:1.

[0049] Example 4 The difference between this example and Example 2 is only that the preparation steps of the modified phenyl silicone rubber are specifically as follows: (1) Take a 250 ml three-necked flask, add 100 ml of the mixed solvent, then add 7.5 g of nano-silica and 0.5 g of citric acid, raise the system temperature to 45 °C and stir overnight, then add 0.5 g of trifluorooctyltrimethoxysilane, stir at 175 rpm for 6 h, then raise the system temperature to 85 °C for condensation reflux reaction for 2 h, then cool to room temperature, centrifuge at 9000 rpm for 30 min, take the precipitate, wash it twice with absolute ethanol at 40 °C, and then wash it three times with toluene, and dry it at 50 °C to obtain fluorinated carbonized nano-silica.

[0050] All the remaining steps are the same as those in Example 2.

[0051] Example 5 The difference between this example and Example 2 is only that the preparation steps of the activated fluorinated carbonized nano-silica dispersion are specifically as follows: Take 5.5 g of fluorinated carbonized nano-silica, mix it with 0.2 g of activator, 0.7 g of polyvinylpyrrolidone, and 0.2 g of sodium polyacrylate, then adjust the magnetic stirring speed to 120 rpm, adjust the temperature to 55 °C, and obtain it after treatment for 0.5 h.

[0052] All the remaining steps are the same as those in Example 2.

[0053] Comparative Example 1 The difference between this comparative example and Example 2 is only that the preparation steps of the modified phenyl silicone rubber in this comparative example are specifically as follows: Take 53 g of hexamethylcyclotrisiloxane and 15.7 g of diphenylsilane respectively, stir and heat at 45 °C for 3 h. After mixing under a nitrogen atmosphere, place it in 300 ml of toluene, adjust the magnetic stirring speed to 150 rpm, disperse for 10 min, then add 0.5 g of potassium trimethylsilanolate and 6.2 g of activated nano-silica dispersion. Subsequently, raise the system temperature to 105 °C at a rate of 4 °C / min, stir and react for 2 h. Then stop heating. When the temperature drops to 68 °C, add 0.22 g of nickel acetylacetonate, carry out constant temperature reflux treatment for 35 min, immediately add 0.27 g of triphenylphosphine, increase the stirring speed to 300 rpm, treat for 15 min, then add 2.4 g of hexamethyldisiloxane, continue to treat for 0.5 h, and then transfer the mixture to a closed reaction kettle. Under a high magnetic stirring speed of 1500 rpm, treat for 25 min. Then adjust the vacuum degree to -0.1 MPa, adjust the temperature to 65 °C, and treat for 2 h. Finally, wash three times with absolute ethanol and dry to obtain modified phenyl silicone rubber.

[0054] In this comparative example, the preparation steps of the activated nano-silica dispersion are as follows: Take 5.3 g of nano-silica, mix it with 0.1 g of salicylic acid, 0.5 g of polyvinylpyrrolidone, and 0.2 g of sodium polyacrylate, then adjust the magnetic stirring speed to 120 rpm and adjust the temperature to 55 °C and treat for 1 h to obtain it.

[0055] All the other steps are the same as those in Example 2.

[0056] Comparative Example 2 The difference between this comparative example and Example 2 is only that an equal amount of phenyl silicone rubber is taken to replace the modified phenyl silicone rubber and mixed with the other components of the spraying composition to obtain the spraying composition.

[0057] Among them, the phenyl silicone rubber is provided by Sichuan Haokang Technology Co., Ltd.

[0058] All the other steps are the same as those in Example 2.

[0059] Performance detection test Preparation of test samples: (a) Take stainless steel with dimensions of 15 cm × 12 cm × 0.2 cm, polish it with 200-mesh sandpaper, wipe it with absolute ethanol to remove surface oil stains, then place it in a sodium hydroxide solution with a mass concentration of 3.5%, treat at 65 °C for 30 min, and then place it in a 100 °C oven for preheating for standby.

[0060] (b) Take the compositions for spraying in Examples 1-5 and Comparative Examples 1-2, place them in the powder storage tank of a thermal spraying gun, use acetylene as the fuel gas and oxygen as the combustion-supporting agent, spray the coating on the pretreated stainless steel, and control the average thickness of the coating to be 150 microns. Take three groups from each of the examples and comparative examples as test samples.

[0061] SEM test Take the test samples of the compositions for spraying in Example 2 and Comparative Example 1, and conduct SEM testing on the coatings. The results are as Figure 1 shown. Among them, (a) is the SEM image of the coating prepared in Comparative Example 1; (b) is the SEM image of the coating prepared in Example 2.

[0062] Coating surface quality test 1) Bonding strength Use pressure-sensitive tape to attach to the test samples in Examples 1-5 and Comparative Examples 1-2, apply pressure to the bonding position with a 10N weight for 2 minutes, and then quickly tear off the pressure-sensitive tape from the test sample at a 30° angle. Observe the coating peeling situation. Use "no peeling", "slight peeling", and "severe peeling" as the rating criteria.

[0063] 2) Coating hardness Refer to the national standard method of GB / T9275-2008, take the test samples in Examples 1-5 and Comparative Examples 1-2 for scratch testing, and record the scratch length left by the indenter on the coating surface. The rating criteria are as follows: excellent: scratch length ≤ 10mm; good: 10mm < scratch length < 20mm; general: 20mm ≤ scratch length ≤ 25mm; poor: scratch length > 25mm.

[0064] Table 1 Test results of coating surface quality of test samples in Examples 1-5 and Comparative Examples 1-2

[0065] Coating porosity test Take the test samples in Examples 1-5 and Comparative Examples 1-2, strip the coating by wire cutting, and record the apparent volume of the coating as V 1 , after washing the stripped coating with anhydrous ethanol, place it in an oven at 65°C for drying for 2 hours. After sufficient drying, transfer the sample to the mercury intrusion chamber, inject liquid mercury, until the coating sample is completely immersed, then evacuate the mercury intrusion chamber and keep it for 2.5 hours, and record the volume of mercury infiltrated as V 2 . According to the formula: Porosity = V 2 / V 1 × 100% Calculate the porosity of the coatings of the test samples, and the test results are as Figure 2 shown.

[0066] Coefficient of Friction Test Using a ball - disk friction and wear tester, the test conditions were set as follows: the counter - grinding ball was a silicon carbide ball with a diameter of 4 mm, the load was 5.2 N, the sliding speed was 0.19 m / s, and the total sliding distance was 1000 m. Record the coefficient of friction of the coatings in Examples 1 - 5 and Comparative Examples 1 - 2, and calculate the specific wear rate. The test results are as Figure 3 shown.

[0067] By analyzing Examples 1 - 5 and Comparative Examples 1 - 2 and combining with Table 1, it can be seen that the surface quality of the coatings obtained by the Example schemes is at a relatively high level; in the test scheme, the surface quality of the coating in Comparative Example 2 is the worst, and both its bonding strength and coating smoothness results are at a relatively low level, and serious coating peeling occurred during the test process.

[0068] By analyzing Example 2 and Comparative Example 1 and combining with Figure 1 it can be seen that there are dense cracks and large pores in the microscopic state of the coating in Comparative Example 1, which is a manifestation of stress concentration in the coating, indicating that in Comparative Example 1, nano - silica without fluorocarbon treatment was directly used, and the mixing effect of each raw material component of the spraying composition was not excellent. Nano - silica was incorporated into the composition only in a blending rather than bonding form, exacerbating the risk of pore formation in polyether ether ketone; while in the Example 2 scheme, due to the tight interaction between components, stress concentration and a large number of pores in the coating were not caused.

[0069] By analyzing Examples 1 - 5 and Comparative Examples 1 - 2 and combining with Figure 2 and Figure 3 it can be seen that there is an approximately positive - correlation trend between the coating porosity and the friction property, which is consistent with the experimental expectation. The coating porosities of Comparative Example 1 and Comparative Example 2 are high, and macroscopically, the coating roughness is significantly increased; among them, the porosity and coefficient of friction of Comparative Example 2 are the highest in the test groups, which can be explained as follows: adopting the scheme of Comparative Example 2, phenyl silicone rubber was directly used as the raw material component of the spraying composition. Due to the disordered stacking of the phenyl silicone rubber molecular chains, it is difficult to effectively interpenetrate with the semi - crystalline polyether ether ketone polymer during the spraying and cooling process, resulting in a weak coating combination effect and being more prone to shrinkage pores and cracking phenomena.

[0070] By analyzing Examples 1 - 5 and Comparative Examples 1 - 2 and combining with Table 1, Figure 2 and Figure 3 it can be seen that among the seven groups of schemes, the test effect of Example 2 is the best, and the coating obtained by thermal spraying has better surface quality, lower porosity and coefficient of friction.

[0071] This specific embodiment is only an interpretation of the present application and does not limit the present application. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions as needed, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A process for preparing a composition for spraying, characterized in that: The method is prepared from the following raw materials in parts by weight: 80-85 parts of polyetheretherketone powder, 5-8 parts of surface activated silicon carbide powder, 5-7 parts of modified phenyl silicone rubber, 0.5-1 parts of antioxidant, and 0.3-0.5 parts of fumed silica; and comprises the following steps: Take surface activated silicon carbide powder, mix it with polyetheretherketone powder, modified phenyl silicone rubber, antioxidant and fumed silica at high speed to obtain; Wherein, the preparation of modified phenyl silicone rubber comprises the following steps: (1) Take nano-silica, add an activator, disperse in a mixed solvent, then heat and stir overnight, add fluoroorganosilane, then continue heating, cool and centrifuge, take the precipitate, wash, and dry to obtain fluorocarbon nano-silica; (2) Take hexamethylcyclotrisiloxane and diphenylsilane, dehydrate and mix and disperse them, add potassium trimethylsilanol and activated fluorocarbon nano-silica dispersion, gradient temperature reaction, then cool down, add oligomerization agent, reflux at constant temperature, then add triphenylphosphine for further treatment, finally add hexamethyldisiloxane for end-capping, stir at high speed, evaporate the solvent in vacuum, wash with alcohol and dry to obtain modified phenyl silicone rubber.

2. The process for preparing a composition for spraying according to claim 1, characterized in that: The preparation of the surface activated silicon carbide powder comprises the following steps: taking silicon carbide powder, washing with alcohol and drying it, placing it in a silane coupling agent dispersion for ultrasonic treatment at 60-65° C. for 3-4 hours, then filtering out the precipitate, washing with alcohol and drying it to obtain the precipitate; the silane coupling agent dispersion is obtained by mixing γ-aminopropyltriethoxysilane and deionized water in a mass ratio of (50-100):

1.

3. The process for preparing a composition for spraying according to claim 1, characterized in that: In the step (1), the activator is one of quinic acid, salicylic acid, L-ascorbic acid and citric acid.

4. The process for preparing a composition for spraying according to claim 1, characterized in that: In the step (1), the mass ratio of nano-silica, activator and fluoroorganosilane is 7.5:(0.2-0.5):(0.5-0.8); the fluoroorganosilane is one of trifluoropropylmethyl silicone oil, (trifluoromethyl)trimethylsilane and tridecafluorooctyltrimethoxysilane; and the mixed solvent is obtained by mixing deionized water and propylene glycol in a volume ratio of (1.5-2):

1.

5. The process for preparing a composition for spraying according to claim 1, characterized in that: In the step (2), the mass ratio of hexamethylcyclotrisiloxane to diphenylsilane raw materials is (52.5-55.6): (15.2-16.5).

6. The process for preparing a composition for spraying according to claim 1, characterized in that: In the step (2), the activated fluorocarbonated nano-silica dispersion is prepared by mixing fluorocarbonated nano-silica, an activator, polyvinyl pyrrolidone and sodium polyacrylate in a mass ratio of (5.2-5.5): (0.1-0.2): (0.5-0.7): (0.2-0.3), and treating the mixture at 50-60° C. for 0.5-1 h.

7. The process for preparing a composition for spraying according to claim 1, characterized in that: In the step (2), the specific operation of the gradient temperature increase is to increase the system temperature to 105-110°C at a rate of 3.7-4.5°C / min.

8. The process for preparing a composition for spraying according to claim 1, characterized in that: In the step (2), the oligomerizing agent is nickel acetylacetonate.

9. The process for preparing a composition for spraying according to claim 1, characterized in that: In the step (2), the constant temperature reflux treatment time is 35-40 minutes; in the step (2), the high-speed stirring is controlled at a stirring speed of 1000-2000 rpm, and the treatment time is 10-30 minutes.

10. A composition for spraying obtained by any one of the preparation processes of claims 1 to 9.

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