A composition for spraying and its preparation process

Abstract

This application relates to the technical field of thermal spray coatings, and specifically discloses a composition for spraying and its preparation process. The composition for spraying 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; the modified phenyl silicone rubber is obtained by mixing and treating fluorinated carbonized nano-silica with phenyl silicone rubber monomer. For the composition for spraying obtained by the solution of this application, the porosity of the coating obtained by thermal spraying is < 2.5%, the friction coefficient is < 0.34, and the specific wear rate is < 9.1×10<supgt;‑6< / supgt;mm<supgt;3< / supgt; / (N·m).

Description

Technical Field

[0001] The present application relates to the technical field of thermal spray coatings, and more specifically, to a composition for spraying and a preparation process thereof. Background Art

[0002] Thermal spraying is a surface processing method that uses a heat source (such as plasma arc, flame, electric arc, etc.) to heat the spray material to a molten or semi-molten state, and then sprays the molten material onto the substrate surface through a high-speed airflow to form a coating. It can significantly improve the surface properties of the material and extend the service life of parts. Therefore, it plays a key role in many fields. Commonly used thermal spraying 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 the action of heat-mechanics, the melted polyetheretherketone is accelerated by the high-speed airflow generated by the heat source, hits the pre-treated substrate surface, and then quickly spreads and cools and solidifies to finally obtain a coating. Although the preparation process of this coating is simple, and the polyetheretherketone coating can be firmly attached to the substrate after forming, the splashing of the molten polyetheretherketone can easily cause the porosity of the obtained polyetheretherketone coating to increase.

[0004] Due to the temperature difference between the substrate and the molten PEEK during the spraying process, the semi-crystalline PEEK spreads for only a very short time before rapidly cooling and forming microparticles. The particle stacking and incomplete contact lead to a significant increase in the porosity of the coating. In order to solve the porosity problem of PEEK thermal spraying, in addition to preheating the substrate, the current commonly used solution is to apply a layer of low-viscosity coating to the substrate after the PEEK coating has cooled, and to achieve the purpose of reducing the porosity by virtue of the penetration of the low-viscosity coating into the PEEK coating. However, this treatment method is prone to increase the coating thickness problem, and after the applied low-viscosity coating solidifies, a small portion of it will remain in the outermost layer of the substrate, hindering the effect of the inner PEEK coating.

[0005] The Chinese patent application document with application publication number CN104789086A discloses a high temperature resistant thermal spray sealer and its use method. In the application scheme, resin, filler, curing agent, metal powder, etc. are mixed to prepare the sealer. The sealer has good permeability and stability. After being applied, it can block the pores of the coating through penetration, and the obtained coating has significantly enhanced wear resistance and corrosion resistance.

[0006] In the above application solution, although the provided thermal spraying sealant and its use method solve the problem of the increase in the porosity of polyether ether ketone thermal spraying to a certain extent, 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 polyether ether ketone thermal spraying and simplify the film-forming process at the same time. Summary of the Invention

[0007] In order to further reduce the problem of excessive porosity of the polyether ether ketone 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 of raw materials including the following 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 silicone rubber, 0.5-1 part of antioxidant, and 0.3-0.5 part of fumed silica; the process includes the following steps:

[0009] Take the surface-activated silicon carbide powder and mix it with polyether ether ketone powder, modified phenyl silicone rubber, antioxidant, and fumed silica at high speed to obtain the composition.

[0010] Among them, the preparation of the modified phenyl silicone rubber includes the following steps:

[0011] (1) Take nano-silica, add an activator, disperse it in a mixed solvent, then heat up and stir overnight, add fluorinated organosilane, then continue to heat up and treat, cool and centrifuge, take the precipitate, wash it, and dry it to obtain fluorinated carbonized nano-silica.

[0012] (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 down, add an oligomerizing 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.

[0013] 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 nucleus, and hexamethylcyclotrisiloxane and diphenylsilane serve as the binding 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 polyether ether ketone 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 nucleus, and a locally regular structure is formed near the nucleus. The formation of this locally 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 composite with a crystallization property between semi-crystalline and amorphous. Due to the increase in the degree of disorder of the chain segments, the crystallization behavior of polyether ether ketone in the composition is inhibited, and the coating has a more sufficient spreading time, ultimately achieving the effect of reducing pores.

[0014] 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 and ultrasonicate it 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.

[0015] By adopting the above technical solutions, through the treatment with silane coupling agents, the mixing effect between the silicon carbide powder and polyether ether ketone in the melt can be improved, and the coating quality can be improved.

[0016] Preferably, in the step (1), the activator is one of quinic acid, salicylic acid, L-ascorbic acid, and citric acid;

[0017] The mass ratio of the nano-silica, activator, and fluorinated organosilane used is 7.5:(0.2 - 0.5):(0.5 - 0.8);

[0018] The fluorinated organosilane is one of trifluoropropylmethyl silicone oil, (trifluoromethyl)trimethylsilane, and tridecafluorooctyltrimethoxysilane;

[0019] The mixed solvent is obtained by mixing deionized water and propylene glycol in a volume ratio of (1.5 - 2):1.

[0020] By adopting the above technical solution, treating nano-silica with plant-derived organic acid gently can improve the reaction activity of nano-silica and fluoro-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.

[0021] By adopting the above technical solution, the fluorinated carbon nano-silica obtained using the above raw materials and ratios has the best effect.

[0022] Preferably, in the step (2), the mass ratio of hexamethylcyclotrisiloxane to diphenylsilane raw materials is (52.5 - 55.6):(15.2 - 16.5).

[0023] 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 segments 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 molecules less likely to decompose at high temperatures.

[0024] Preferably, in the step (2), the activated fluorinated carbon nano-silica dispersion liquid is obtained by mixing fluorinated carbon nano-silica, activator, polyvinylpyrrolidone, 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 then treating at 50 - 60 °C for 0.5 - 1 h.

[0025] By adopting the above technical solution, using the raw materials in the above ratios can further activate the fluorinated carbon nano-silica and play a better nucleation effect in the subsequent preparation process of medium-phenyl silicone rubber.

[0026] 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.

[0027] By adopting the above technical solution, a reaction environment can be provided here for the ring-opening of hexamethylcyclotrisiloxane and the pre-nucleation 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 promote the reaction more gently.

[0028] Preferably, in the step (2), the oligomerization agent is nickel acetylacetonate; the constant temperature reflux treatment time is 35 - 40 min.

[0029] By adopting the above technical solution, using nickel acetylacetonate with low polymerization catalytic effect can control the polymerization process of medium phenyl silicone rubber. By controlling the constant temperature reflux time, the situation of too fast polymerization of raw materials can be avoided; the subsequently added triphenylphosphine can chelate with nickel acetylacetonate to prevent the continuous progress of the catalytic polymerization reaction. Cooperating with the end-capping agent hexamethyldisiloxane, the termination of the catalytic polymerization reaction can be finally achieved.

[0030] Preferably, in the step (2), the high-speed stirring controls the stirring speed to be 1000 - 2000 rpm and the treatment time is 10 - 30 min.

[0031] 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 raw material component of the composition for spraying.

[0032] In the second aspect, the composition for spraying is prepared by the above preparation process in this application.

[0033] To sum up, this application has the following beneficial effects:

[0034] 1. In this application, fluorinated and carbonized nano-silica is used as the central nucleus, and through the combined reaction with the synthetic monomers of phenyl silicone rubber, modified phenyl silicone rubber is prepared. After fluorination and carbonization modification, the nano-silica has a lower surface energy, which can make the synthetic monomers of phenyl silicone rubber more likely 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.

[0035] 2. For the composition for thermal spraying obtained by the solution of this application, the porosity of the coating obtained by thermal spraying is < 2.5%, the friction coefficient is < 0.34, and the specific wear rate is < 9.1×10 -6 mm 3 / (N·m). Description of the Drawings

[0036] Figure 1 This is the SEM image of the coating obtained by thermal spraying for the test samples of the composition for thermal spraying in Example 2 and Comparative Example 1 of this application.

[0037] Figure 2 This is the porosity of the coating obtained by thermal spraying for the test samples of the composition for thermal spraying in Examples 1-5 and Comparative Examples 1-2 of this application.

[0038] Figure 3 This is the friction coefficient and specific wear rate of the coating obtained by thermal spraying for the test samples of the composition for thermal spraying in Examples 1-5 and Comparative Examples 1-2 of this application. Detailed Description of the Invention

[0039] Example 1

[0040] In this example, the composition for thermal spraying is made from 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:

[0041] 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.

[0042] In this embodiment, the preparation steps of the modified phenyl silicone rubber are as follows:

[0043] (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, stir at 150 rpm for 6 h. Subsequently, raise the temperature of the system to 70 °C and carry out 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 at 45 °C to obtain fluorinated carbonized nano-silica.

[0044] (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, 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, stir and react for 2 h. After that, stop heating. When the temperature drops to 65 °C, add 0.2 g of nickel acetylacetonate, carry out constant temperature reflux treatment for 35 min. Immediately add 0.23 g of triphenylphosphine, increase the stirring speed to 300 rpm, treat for 5 min. Then add 2.2 g of hexamethyldisiloxane, continue to treat for 0.5 h. Then transfer the mixture to a closed reaction kettle, treat at a high magnetic stirring speed of 1000 rpm for 10 min. After that, adjust the vacuum degree to -0.1 MPa, adjust the temperature to 65 °C, and treat for 2 h. Finally, wash it three times with absolute ethanol and dry to obtain the modified phenyl silicone rubber.

[0045] In this embodiment, the preparation steps of the surface-activated silicon carbide powder are as follows:

[0046] Take 4.5 g of silicon carbide powder, wash and dry it with absolute ethanol, then 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.

[0047] In this embodiment, the preparation steps of the activated fluorinated carbonized nano-silica dispersion are as follows:

[0048] 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. Then adjust the magnetic stirring speed to 100 rpm, adjust the temperature to 50 °C, and treat for 0.5 h to obtain it.

[0049] Among them, the polyether ether ketone 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 50:1. The mixed solvent is obtained by mixing deionized water and propylene glycol in a volume ratio of 1.5:1.

[0050] Example 2

[0051] In this example, the composition for spraying is made from the following raw materials by weight: 82 g of polyether ether ketone 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:

[0052] 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 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.

[0053] In this example, the preparation steps of the modified phenyl silicone rubber are specifically as follows:

[0054] (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 absolute ethanol at 40 °C, and then wash it three times with toluene, and dry it at 45 °C to obtain fluorinated carbonized nano-silica.

[0055] (2) Weigh 53 g of hexamethylcyclotrisiloxane and 15.7 g of diphenylsilane respectively. Stir and heat them at 45 °C for 3 h. After mixing them under a nitrogen atmosphere, place them in 300 ml of toluene. Adjust the magnetic stirring speed to 150 rpm and 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 temperature of the system to 105 °C at a rate of 4 °C / min and stir and react for 2 h. Then stop heating. Wait until 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 and treat for 15 min. Then add 2.4 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 1500 rpm for 25 min. Then 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 anhydrous ethanol and dry it to obtain modified phenyl silicone rubber.

[0056] In this example, the preparation steps of the surface-activated silicon carbide powder are as follows:

[0057] Take 4.7 g of silicon carbide powder. After washing and drying it with anhydrous ethanol, place it in 50 ml of 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 anhydrous ethanol to obtain it.

[0058] In this example, the preparation steps of the activated fluorinated carbonized nano-silica dispersion are as follows:

[0059] 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 treat for 1 h to obtain it.

[0060] 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 according to a mass ratio of 75:1. The mixed solvent is obtained by mixing deionized water and propylene glycol according to a volume ratio of 1.5:1.

[0061] Example 3

[0062] In this embodiment, the composition for spraying is made from raw materials with the following weights: 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, and 0.5 g of fumed silica; the specific steps are as follows:

[0063] Take the 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.

[0064] In this embodiment, the preparation steps of the modified phenyl silicone rubber are specifically as follows:

[0065] (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 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.

[0066] (2) Respectively take 55.6 g of hexamethylcyclotrisiloxane and 16.5 g of diphenylsilane, 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 and disperse for 20 min, then add 0.6 g of potassium trimethylsilanolate and 6.5 g of activated fluorinated carbonized nano-silica dispersion, then 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, wait for the temperature to drop 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 and process for 20 min, then add 2.5 g of hexamethyldisiloxane and continue to process for 1 h, then transfer the mixture to a closed reaction kettle, under a high magnetic stirring speed of 2000 rpm, process for 30 min, then adjust the vacuum degree to -0.1 MPa and adjust the temperature to 65 °C and process for 2 h, and finally wash it three times with absolute ethanol and dry it to obtain the modified phenyl silicone rubber.

[0067] In this embodiment, the preparation steps of the surface-activated silicon carbide powder are specifically as follows:

[0068] Take 4.8 g of silicon carbide powder. After washing and drying with absolute ethanol, place it in 50 ml of a silane coupling agent dispersion liquid. Adjust the temperature to 65 °C and ultrasonically treat it at 22.5 kHz for 4 h. Finally, filter to obtain the precipitate, and wash and dry it again with absolute ethanol to obtain it.

[0069] In this example, the preparation steps of the activated fluorinated carbonized nano-silica dispersion liquid are as follows:

[0070] Take 5.5 g of fluorinated carbonized nano-silica, mix it with 0.2 g of L-ascorbic acid, 0.7 g of polyvinylpyrrolidone, and 0.3 g of sodium polyacrylate. After adjusting the magnetic stirring speed to 120 rpm and the temperature to 60 °C, process it for 1 h to obtain it.

[0071] 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 liquid 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.

[0072] Example 4

[0073] The difference between this example and Example 2 is only that the preparation steps of the modified phenyl silicone rubber are as follows:

[0074] (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 temperature of the system to 45 °C and stir overnight. Then add 0.5 g of trifluorooctyltrimethoxysilane and stir at 175 rpm for 6 h. Subsequently, raise the temperature of the system to 85 °C and carry out a 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.

[0075] All the remaining steps are the same as those in Example 2.

[0076] Example 5

[0077] The difference between this example and Example 2 is only that the preparation steps of the activated fluorinated carbonized nano-silica dispersion liquid are as follows:

[0078] 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. After adjusting the magnetic stirring speed to 120 rpm and the temperature to 55 °C, process it for 0.5 h to obtain it.

[0079] All the remaining steps are the same as those in Example 2.

[0080] Comparative Example 1

[0081] The difference between this comparative example and Example 2 lies only in that the preparation steps of the modified phenyl silicone rubber in this comparative example are specifically as follows:

[0082] Respectively take 53 g of hexamethylcyclotrisiloxane and 15.7 g of diphenylsilane, stir and heat at 45 °C for 3 h, mix them under a nitrogen atmosphere, place them 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 liquid. 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, perform 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, and treat it at a high magnetic stirring speed of 1500 rpm 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 it three times with absolute ethanol, and obtain the modified phenyl silicone rubber after drying.

[0083] In this comparative example, the preparation steps of the activated nano-silica dispersion liquid are as follows:

[0084] 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 the temperature to 55 °C, and treat for 1 h to obtain it.

[0085] All the remaining steps are the same as those in Example 2.

[0086] Comparative Example 2

[0087] The difference between this comparative example and Example 2 lies only in that an equal amount of phenyl silicone rubber is taken to replace the modified phenyl silicone rubber and mixed with the remaining components of the spraying composition to obtain the spraying composition.

[0088] Among them, the phenyl silicone rubber is provided by Sichuan Haokang Technology Co., Ltd.

[0089] All the remaining steps are the same as those in Example 2.

[0090] Performance detection test

[0091] Preparation of test samples:

[0092] (a)Take a stainless steel with dimensions of 15 cm × 12 cm × 0.2 cm. After polishing with 200-mesh sandpaper, wipe it with absolute ethanol to remove the surface oil stain. Then place it in a sodium hydroxide solution with a mass concentration of 3.5% and treat it at 65 °C for 30 min. Then place it in an oven preheated to 100 °C for standby.

[0093] (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 of each example and comparative example as test samples.

[0094] SEM test

[0095] Take the test samples applied with 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.

[0096] Coating surface quality test

[0097] 1) Bonding strength

[0098] Use pressure-sensitive tape to attach to the test samples of the schemes in Examples 1-5 and Comparative Examples 1-2. Use a 10 N weight to apply pressure to the bonding position for 2 min. Then quickly tear off the pressure-sensitive tape at a 30° angle to the test sample and observe the coating peeling situation. Use "no peeling", "slight peeling", and "severe peeling" as the rating criteria.

[0099] 2) Coating hardness

[0100] Refer to the national standard method of GB / T9275-2008. Take the test samples of Examples 1-5 and Comparative Examples 1-2 for scratch testing, and record the scratch length left by the indentor on the coating surface. The rating criteria are as follows: excellent: scratch length ≤ 10 mm; good: 10 mm < scratch length < 20 mm; general: 20 mm ≤ scratch length ≤ 25 mm; poor: scratch length > 25 mm.

[0101] Table 1 Test results of the coating surface quality of the test samples in Examples 1-5 and Comparative Examples 1-2

[0102]

[0103] Coating porosity test

[0104] Take the test samples of Examples 1-5 and Comparative Examples 1-2, and strip the coating by wire cutting. The apparent volume of the coating is denoted as V1. After washing the stripped coating with absolute ethanol, place it in an oven at 65 °C for drying for 2 h. After sufficient drying, transfer the sample to the mercury intrusion chamber, inject liquid mercury, and after the coating sample is completely immersed, evacuate the mercury intrusion chamber and maintain it for 2.5 h, and record the volume V2 of mercury infiltration. According to the formula:

[0105] Porosity = V2 / V1×100%

[0106] Calculate the porosity of the coating of the test sample, and the test results are as Figure 2 shown.

[0107] Coefficient of friction test

[0108] Use a ball-on-disk friction and wear tester, and set the test conditions as follows: the counterface ball is a silicon carbide ball with a diameter of 4 mm, the load is 5.2 N, the sliding speed is 0.19 m / s, and the total sliding distance is 1000 m. Record the coefficient of friction of the coatings of Examples 1-5 and Comparative Examples 1-2, and calculate the specific wear rate. The test results are as Figure 3 shown.

[0109] Analysis of Examples 1-5 and Comparative Examples 1-2 and in combination with Table 1 shows that the surface quality of the coatings obtained by the Example solutions is at a relatively high level; in the test solutions, the surface quality of the coating in Comparative Example 2 is the worst, and its bonding strength and coating smoothness results are both at a relatively low level, and serious coating peeling occurred during the test process.

[0110] Analysis of Example 2 and Comparative Example 1 and in combination with Figure 1 shows 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 directly using nano-silica without fluorocarbon treatment in Comparative Example 1, the mixing effect of each raw material component of the spraying composition is not excellent, and nano-silica is incorporated into the composition only in the form of blending rather than bonding, which exacerbates the pore-forming risk of polyetheretherketone; while in the solution of Example 2, due to the close interaction between the components, stress concentration and a large number of pores in the coating are not caused.

[0111] Analysis of Examples 1-5 and Comparative Examples 1-2 and in combination with Figure 2 and Figure 3It can be seen that the coating porosity is approximately positively correlated with the friction properties, which is consistent with the experimental expectation. The coating porosities of Comparative Example 1 and Comparative Example 2 are high, and macroscopically, it is manifested as a significant increase in the coating roughness. Among them, the porosity and friction coefficient of Comparative Example 2 are the highest in the test groups. This can be explained as follows: In the scheme of Comparative Example 2, phenyl silicone rubber is directly used as the raw material component of the composition for spraying. 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 more prone to shrinkage holes and cracking phenomena.

[0112] Analyze Examples 1-5 and Comparative Examples 1-2 and combine 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. The coating obtained by thermal spraying has better surface quality, lower porosity and friction coefficient.

[0113] This specific embodiment is only an explanation of the present application, and it is not a limitation of the present application. Those skilled in the art can make modifications without creative contributions to this embodiment according to needs after reading this specification, 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.

Images