Low-temperature plasma spraying method for heat-sensitive polymer matrix and composite material

Abstract

The invention provides a low-temperature plasma spraying method for a heat-sensitive polymer matrix and a composite material, and belongs to the technical field of surface engineering. According to the method, through a system process of matrix surface pretreatment, spraying powder drying and low-temperature plasma spraying, the core is that a matrix active cooling technology is adopted in the range of 0-10 DEG C to isolate the plasma arc heat influence, and optimized sand blasting coarsening, powder granularity control and spraying process parameters are matched; and the compact Al2O3-TiO2 ceramic coating with high bonding strength is successfully prepared on a heat-sensitive epoxy resin matrix. The limitation that a traditional thermal spraying technology cannot be used for high polymer materials is broken through, the technological process is simple, the cost is low, and the obtained coating is excellent in abrasion resistance and suitable for meeting the requirement for high performance of the surface of the light high polymer material in the fields of electronic equipment, aerospace and the like.

Description

Technical Field

[0001] This invention relates to the interdisciplinary field of surface functionalization and remanufacturing of polymer materials, specifically to a low-temperature plasma spraying method for achieving a high-strength bonded ceramic coating on a heat-sensitive epoxy resin matrix through active thermal management strategies and multi-scale interface control, and particularly to a low-temperature plasma spraying method for heat-sensitive polymer matrices and a composite material. Background Technology

[0002] Epoxy resin sheets are widely used in electronic device housings, printed circuit board substrates, aerospace interior parts, and industrial molds due to their excellent electrical insulation, lightweight, chemical resistance, and good molding and processing properties. However, epoxy resin itself has low hardness and poor wear resistance, making its surface easily damaged when subjected to friction, scratches, or particle erosion. This not only affects the appearance of the product but also impairs its functionality and service life.

[0003] Currently, methods for surface hardening of epoxy resin mainly include: surface coating: such as chemical plating or electroplating to form a metal or alloy layer. This method has problems such as complex processes, poor adhesion between the coating and the resin substrate, easy peeling, and unsuitability for non-conductive overall surface treatment; coating with organic coatings: such as spraying polyurethane, fluorocarbon resin, and other hard coatings. Although this method can improve surface properties to some extent, its hardness improvement is limited, and its wear resistance still cannot meet the requirements of harsh working conditions; applying protective films: this method is simple, but the film layer is prone to aging and scratching, and the interfacial adhesion is weak, making it a temporary protective measure.

[0004] Plasma spraying, as a mature surface strengthening technology, can melt various metal and ceramic powder materials and spray them at high speed onto the substrate surface to form a high-performance coating. However, when applied to epoxy resin substrates, it faces three fundamental technical challenges: 1) The contradiction between thermal shock and thermal accumulation: The high heat flux of plasma jets can cause instantaneous thermal degradation of epoxy resin in micro-areas.

[0005] 2) The contradiction between bonding strength and thermal stress: The huge difference in the coefficient of thermal expansion between ceramics and resins, under high heat input, introduces interfacial stress that causes the coating to crack or peel off.

[0006] 3) Activation energy and reaction temperature conflict: There is an inherent conflict between the high activation energy required for the melting of ceramic particles and the low tolerance temperature window of epoxy resin.

[0007] These contradictions prevent conventional plasma spraying technology from being directly applied to epoxy resin-based polymer materials. Therefore, developing a low-temperature, efficient, and strongly bonded spraying method that can adapt to the thermal sensitivity of the epoxy resin matrix while imparting a high-hardness, high-wear-resistance ceramic coating to its surface has become a pressing technical problem to be solved in this field. Summary of the Invention

[0008] The purpose of this invention is to provide a novel technical solution to resolve the technical contradictions in the "high enthalpy spray source-low heat capacity substrate" system.

[0009] This invention addresses the problems of thermal damage risk, poor coating adhesion, and complex processes in existing technologies by providing a low-temperature plasma spraying method. This method establishes a new technological system suitable for heat-sensitive polymer substrates. Its core lies in isolating thermal damage through active thermal management and achieving high-strength coating adhesion through interface control.

[0010] The core innovations of this invention include: Construction of pretreatment interface and formation of thermal buffer layer: Surface pretreatment: By sandblasting with spherical white corundum abrasive with a particle size of 50–100 μm at an air pressure of 0.3–0.6 MPa, a pitted surface and compacted matrix structure were precisely constructed on the epoxy resin surface, forming a tight thermal barrier morphology close to the surface. This structure greatly increases the bonding area, and the localized compaction treatment constitutes a physical buffer zone to cope with thermal shock during subsequent spraying.

[0011] Active thermal management strategy: The pretreated epoxy resin matrix is ​​fixed on a fixture with circulating coolant, ensuring that the surface temperature of the matrix is ​​stably maintained within the critical process window of 0–10°C throughout the spraying process. This temperature range represents a safety-performance balance point verified through extensive experimentation. It ensures that the coating is formed instantly upon impact of molten particles while keeping the matrix within a safe zone below its glass transition temperature, fundamentally preventing thermal degradation of the epoxy material.

[0012] The optimized "low-temperature, high-throughput" spraying process resolves the conflict between activation energy and reaction temperature. An atmospheric plasma spraying system is employed, optimizing the plasma gas (including argon and hydrogen) ratio and energy parameters (current 300-500A, voltage 20-30V) to generate a short-duration, high-speed, high-momentum particle stream. This process effectively replaces high-heat input with high-kinetic-energy deposition, ensuring complete powder melting while minimizing heat transfer to the substrate. Rapidly moving the spray jet during spraying prevents localized overheating. Through process control, a large, semi-molten sprayed particle deposition layer is formed on the epoxy resin substrate surface, acting as a thermal insulation barrier.

[0013] The technical solution of this invention is as follows: I. Surface pretreatment of epoxy resin board substrate: Surface cleaning and degreasing of epoxy resin substrate: Using epoxy resin substrate as the substrate, the substrate is rinsed with room temperature cold water to remove some mechanical debris remaining on the surface and in the pores. Then, the substrate is placed in an ultrasonic cleaner, and anhydrous ethanol and analytical grade acetone are used sequentially as solvents to remove organic oil stains and fingerprint residues from the epoxy resin surface. The cleaning time for each solvent is 10 minutes, and the frequency is 40KHz. Cavitation effect is used to remove stubborn contaminants. The surface is then sprayed with deionized water to remove residual solvents. After cleaning, it is placed in a 50℃ forced-air drying oven for 30 minutes to dry.

[0014] Sandblasting treatment of epoxy resin matrix: After cleaning and degreasing the surface of the epoxy resin substrate, a sandblasting machine is used for fine-particle sandblasting. White spherical alumina (white corundum) abrasive is selected, with a particle size controlled between 50 and 100 μm. The air pressure range is controlled between 0.3 and 0.6 MPa. The sandblasting distance is controlled at approximately 100 to 150 mm, and the sandblasting angle is 70 to 90° (perpendicular to the surface).

[0015] After sandblasting, the epoxy resin matrix is ​​repeatedly sprayed and washed with anhydrous ethanol to remove sand particles from the surface and pores of the epoxy resin matrix. Finally, it is dried with compressed air to complete the surface pretreatment of the epoxy resin matrix.

[0016] II. Selection and Pretreatment of Coating Powder: Selection and characteristics of raw material powders: This invention utilizes pre-synthesized Al2O3-TiO2 composite powder (AT powder). Based on the final coating performance requirements, two classic formulations are selected: Al2O3-13%TiO2 and Al2O3-40%TiO2. The selected powders are required to have a chemical purity of no less than 98.5%, a total content of major impurities of less than 1.5%, and a particle size distribution ranging from 15 to 45 μm.

[0017] Powder drying process: Place the powder in an alumina ceramic crucible or stainless steel tray, with a layer thickness not exceeding 20 mm. Then place the container containing the powder in a drying oven and dry continuously at 50°C for 12 hours. The dried powder should be immediately transferred to a sealed, moisture-proof container, or directly loaded into the powder feeder of the spraying equipment and purged with a dry protective gas (including argon).

[0018] III. Plasma spraying process: Matrix precooling: The pretreated epoxy resin matrix is ​​fixed on a fixture with circulating coolant to maintain the surface temperature of the matrix at a stable range of 0-10°C throughout the spraying process. A schematic diagram of the fixture is attached. Figure 1As shown, it consists of a circulating cooling water tank, a circulating pump, a fixture panel, and internal cooling water circulation pipes. The circulating water tank contains a cooling device to control the water temperature between 0-10℃. The cooling water in the tank enters the circulating water pipes inside the fixture via the circulating pump. The circulating water pipes maintain the surface temperature of the fixture within the range of 0-10℃, preventing overheating of the epoxy resin matrix fixed on the fixture.

[0019] Spraying system and parameters: This invention employs an atmospheric plasma spraying system, using argon and hydrogen as the plasma gases. The spraying gas pressure is 0.5-0.7 MPa, the spraying current is 350-500 A, the voltage is 20-30 V, the powder delivery gas is argon, the powder delivery flow rate is 300 L / h, and the spraying distance is 150-300 mm. The epoxy resin substrate, fixed on the fixture, reciprocates along a straight line for a distance of 180 mm at a speed of 20-30 mm / s.

[0020] After one coat of spraying, a semi-molten ceramic protective layer is formed on the surface. Then, the process parameters are adjusted to the conventional spraying method, namely, spraying voltage 580-600A, voltage 25-35V, spraying distance 100-120mm, and moving speed 10-20 mm / s, finally preparing a 200-300μm protective plasma spray coating on the epoxy resin substrate surface.

[0021] This invention employs a thermal spraying method to prepare a wear-resistant coating. Specifically, it utilizes plasma spraying equipment and Al2O3-TiO2 composite powder as the raw material to form an alumina-titanium oxide ceramic hard wear-resistant coating on the surface of an epoxy resin matrix, thereby improving surface hardness and wear resistance. Using Al2O3-TiO2 composite powder as the spraying raw material, an optimized low-temperature spraying process directly forms a dense ceramic layer on the substrate surface. This avoids thermal damage to the epoxy resin matrix and eliminates the complex pretreatment steps required for preparing specially structured spraying powders, shortening the process flow, reducing production costs, and resulting in a wear-resistant coating with strong adhesion and excellent performance.

[0022] The advantages and beneficial effects of this invention are: Breaking through thermal barrier limitations: For the first time, plasma spraying ceramic coating was achieved on the surface of heat-sensitive epoxy resin, solving the industry problem that traditional high-temperature spraying cannot be used for polymer materials; High bonding strength: Combining sandblasting roughening and substrate cooling, a strong and tough bond is achieved between the coating and the substrate; Excellent wear resistance: The resulting AT coating is dense and uniform, significantly improving its resistance to abrasive wear and adhesive wear; Simple process and low cost: It directly uses commercial AT powder, without the need for pre-sintering or complex pretreatment, making it suitable for large-scale production; Wide applicability: It can be extended to the surface functionalization treatment of other thermoplastic or thermosetting polymer materials. Attached Figure Description

[0023] Figure 1 This is a structural diagram of a circulating cooling fixture; Figure 2 The morphology of the coating prepared in Example 1; Figure 3 The morphology image of the coating prepared in Example 2; Figure 4 The image shows the morphology of the coating prepared in Example 3. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0025] Example 1: An epoxy resin board with dimensions of 30mm×30mm×5mm was used as the substrate. The epoxy resin board substrate was rinsed with room temperature cold water to remove some mechanical debris remaining on the surface and in the pores. Then, the substrate was placed in an ultrasonic cleaner, and anhydrous ethanol and analytical grade acetone were used as solvents in sequence to remove organic oil stains, fingerprints and release agent residues from the epoxy resin surface. The cleaning time for each solvent was 10 minutes, and the frequency was 40KHz. The cavitation effect was used to remove stubborn contaminants. The surface was then sprayed with deionized water to remove residual solvents. After cleaning, it was placed in a 50℃ forced-air drying oven for 30 minutes to dry.

[0026] After cleaning and degreasing the epoxy resin substrate surface, a sandblasting machine is used for fine-particle sandblasting. Spherical white alumina (white corundum) abrasive is selected, with a particle size controlled between 50 and 60 μm. The air pressure is controlled within the range of 0.5 MPa. The sandblasting distance is controlled at approximately 140 mm, and the sandblasting angle is 90° (perpendicular to the surface).

[0027] After sandblasting, the epoxy resin matrix is ​​repeatedly sprayed and washed with anhydrous ethanol to remove sand particles from the surface and pores of the epoxy resin matrix. Finally, it is dried with a hair dryer to complete the surface pretreatment of the epoxy resin matrix.

[0028] The Al2O3-13%TiO2 composite powder with a pre-synthesized chemical purity of not less than 98.5%, a total content of major impurities of less than 1.5%, and a particle size distribution range of 15-45 μm is used.

[0029] The powder was placed in a stainless steel tray, with a layer thickness of 10 mm. The container then was placed in a drying oven and dried continuously at 50°C for 12 hours. After drying, the powder was immediately transferred to a sealed, moisture-proof container.

[0030] The pretreated epoxy resin matrix is ​​fixed on a fixture with circulating coolant to keep the surface temperature of the matrix stable at 0~10℃ throughout the spraying process.

[0031] The SX-80 plasma spraying equipment manufactured by Guangzhou Sanxin Technology Co., Ltd. was used. The plasma gases used were argon and hydrogen. The spraying gas pressure was 0.7 MPa, the spraying current was 480 A, the voltage was 27 V, the powder feeding gas was argon, the powder feeding flow rate was 300 L / h, and the spraying distance was 300 mm. The epoxy resin substrate, fixed on the fixture, moved reciprocatingly along a straight line for a distance of 180 mm at a speed of 20 mm / s.

[0032] The process parameters were adjusted to the conventional spraying method, namely, spraying voltage 580A, voltage 32V, spraying distance 1000mm, and moving speed 15 mm / s, and finally a 250μm protective plasma spray coating was prepared on the epoxy resin substrate surface.

[0033] Example 2: An epoxy resin board with dimensions of 30mm×30mm×5mm was used as the substrate. The epoxy resin board substrate was rinsed with room temperature cold water to remove some mechanical debris remaining on the surface and in the pores. Then, the substrate was placed in an ultrasonic cleaner, and anhydrous ethanol and analytical grade acetone were used as solvents in sequence to remove organic oil stains, fingerprints and release agent residues from the epoxy resin surface. The cleaning time for each solvent was 10 minutes, and the frequency was 40KHz. The cavitation effect was used to remove stubborn contaminants. The surface was then sprayed with deionized water to remove residual solvents. After cleaning, it was placed in a 50℃ forced-air drying oven for 30 minutes to dry.

[0034] After cleaning and degreasing the epoxy resin substrate surface, a sandblasting machine is used for fine-particle sandblasting. Spherical white alumina (white corundum) abrasive is selected, with a particle size controlled between 50 and 100 μm. The air pressure is controlled within the range of 0.3 MPa. The sandblasting distance is controlled at approximately 100 mm, and the sandblasting angle is 70° (perpendicular to the surface).

[0035] After sandblasting, the epoxy resin matrix is ​​repeatedly sprayed and washed with anhydrous ethanol to remove sand particles from the surface and pores of the epoxy resin matrix. Finally, it is dried with a hair dryer to complete the surface pretreatment of the epoxy resin matrix.

[0036] The Al2O3-40%TiO2 composite powder with a pre-synthesized chemical purity of not less than 98.5%, a total content of major impurities of less than 1.5%, and a particle size distribution range of 15-45 μm is used.

[0037] The powder was placed in a stainless steel tray, with a layer thickness of 10 mm. The container then was placed in a drying oven and dried continuously at 50°C for 12 hours. After drying, the powder was immediately transferred to a sealed, moisture-proof container.

[0038] The pretreated epoxy resin matrix is ​​fixed on a fixture with circulating coolant to keep the surface temperature of the matrix stable at 0~10℃ throughout the spraying process.

[0039] The SX-80 plasma spraying equipment manufactured by Guangzhou Sanxin Technology Co., Ltd. was used. The plasma gases used were argon and hydrogen. The spraying gas pressure was 0.7 MPa, the spraying current was 300 A, the voltage was 21 V, the powder feeding gas was argon, the powder feeding flow rate was 300 L / h, and the spraying distance was 200 mm. The epoxy resin substrate, fixed on the fixture, moved reciprocatingly along a straight line for a distance of 180 mm at a speed of 30 mm / s.

[0040] The process parameters were adjusted to the conventional spraying method, namely, spraying voltage 600A, voltage 25V, spraying distance 120mm, and moving speed 20mm / s, and finally a 200 protective plasma spray coating was prepared on the epoxy resin substrate surface.

[0041] Comparative Example 1: An epoxy resin board with dimensions of 30mm×30mm×5mm was used as the substrate. The epoxy resin board substrate was rinsed with room temperature cold water to remove some mechanical debris remaining on the surface and in the pores. Then, the substrate was placed in an ultrasonic cleaner, and anhydrous ethanol and analytical grade acetone were used as solvents in sequence to remove organic oil stains, fingerprints and release agent residues from the epoxy resin surface. The cleaning time for each solvent was 10 minutes, and the frequency was 40KHz. The cavitation effect was used to remove stubborn contaminants. The surface was then sprayed with deionized water to remove residual solvents. After cleaning, it was placed in a 50℃ forced-air drying oven for 30 minutes to dry.

[0042] After cleaning and degreasing the epoxy resin substrate surface, a sandblasting machine is used for fine-grained sandblasting. Ordinary white alumina (white corundum) abrasive is selected, with a particle size controlled between 50 and 100 μm. The air pressure is controlled between 0.3 and 0.6 MPa. The sandblasting distance is controlled at approximately 100 to 150 mm, and the sandblasting angle is 70 to 90° (perpendicular to the surface).

[0043] After sandblasting, the epoxy resin matrix is ​​repeatedly sprayed and washed with anhydrous ethanol to remove sand particles from the surface and pores of the epoxy resin matrix. Finally, it is dried with a hair dryer to complete the surface pretreatment of the epoxy resin matrix.

[0044] The Al2O3-13%TiO2 composite powder with a pre-synthesized chemical purity of not less than 98.5%, a total content of major impurities of less than 1.5%, and a particle size distribution range of 15-45 μm is used.

[0045] The powder was placed in a stainless steel tray, with a layer thickness of 10 mm. The container then was placed in a drying oven and dried continuously at 50°C for 12 hours. After drying, the powder was immediately transferred to a sealed, moisture-proof container.

[0046] The pretreated epoxy resin matrix is ​​fixed on a standard fixture to keep the surface temperature of the matrix relatively stable relative to room temperature throughout the spraying process.

[0047] The SX-80 plasma spraying equipment manufactured by Guangzhou Sanxin Technology Co., Ltd. was used. The plasma gases used were argon and hydrogen. The spraying gas pressure was 0.7 MPa, the spraying current was 480 A, and the voltage was 27 V. The powder feeding gas was argon, the powder feeding flow rate was 300 L / h, the powder feeding voltage was 3 V, and the spraying distance was 150 mm. The epoxy resin substrate, fixed on the fixture, moved reciprocatingly along a straight line for a distance of 180 mm at a speed of 15 mm / s.

[0048] Matters not covered in this invention are common knowledge.

[0049] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A low-temperature plasma spraying method for heat-sensitive polymer substrates, characterized in that: Includes the following steps: 1) Surface pretreatment steps: The surface of the polymer matrix is ​​cleaned and roughened by sandblasting; 2) Powder preparation steps: Select ceramic composite powder and dry it; 3) Low-temperature spraying step: During the spraying process, the surface temperature of the polymer matrix is ​​maintained within the range of 0-10℃ by an active cooling device, and plasma spraying is performed.

2. The low-temperature plasma spraying method for heat-sensitive polymer substrates according to claim 1, characterized in that, The surface pretreatment step involves sandblasting roughening, which is performed using spherical white alumina sand with a particle size of 50-100 μm, a sandblasting air pressure of 0.3-0.6 MPa, a sandblasting distance of 100-150 mm, and a sandblasting angle of 70-90°.

3. The low-temperature plasma spraying method for heat-sensitive polymer substrates according to claim 1 or 2, characterized in that, In the powder preparation step, the ceramic composite powder is an Al2O3-TiO2 composite powder, the chemical composition of which is selected from Al2O3-13wt% TiO2 or Al2O3-40wt% TiO2, the purity is not less than 98.5%, and the particle size distribution is 15-45 μm.

4. The low-temperature plasma spraying method for heat-sensitive polymer substrates according to claim 1, characterized in that, The drying process involves drying continuously at 50°C for 12 hours.

5. The low-temperature plasma spraying method for heat-sensitive polymer substrates according to claim 1, characterized in that, In the low-temperature spraying step, a circulating coolant fixture is used to actively cool the polymer matrix.

6. The low-temperature plasma spraying method for heat-sensitive polymer substrates according to claim 1, characterized in that, The process parameters for plasma spraying are as follows: the plasma gas is a mixture of argon and hydrogen, the spraying gas pressure is 0.5-0.7 MPa, the spraying current is 350-500 A, the spraying voltage is 20-30 V, the powder feeding gas is argon, the powder feeding flow rate is 300 L / h, and the spraying distance is 150-300 mm.

7. The low-temperature plasma spraying method for heat-sensitive polymer substrates according to claim 5, characterized in that, In the low-temperature spraying step, the polymer matrix reciprocates relative to the spray jet, with a movement distance of 180 mm and a moving speed of 20-30 mm / s.

8. A composite material obtained by the low-temperature plasma spraying method for a heat-sensitive polymer matrix as described in claims 1-7, characterized in that, The composite material has a semi-molten Al2O3-TiO2 ceramic wear-resistant coating on its surface, which can prevent the substrate temperature from becoming too high.

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