A preparation method of layered PEEK composite material used for compressor valve plate

Abstract

The invention discloses a method for preparing a layered PEEK composite material used for a compressor valve plate, belonging to the technical field of composite material preparation technology, including the preparation of an inner layer structure PEEK composite material, the preparation of an outer layer structure PEEK composite material and secondary injection molding. The invention adopts PEEK as a base resin, prepares an inner layer structure material with high mechanical strength and an outer layer structure material with excellent corrosion resistance through composite modification, obtains a layer structure through a secondary injection molding process, enables the product to have excellent corrosion resistance while maintaining the high strength characteristics of PEEK.

Description

Technical Field

[0001] The invention discloses a method for preparing a layered PEEK composite material applied to a compressor air valve plate, belonging to the technical field of composite material preparation technology. Background Art

[0002] The exhaust valve is an important component in the compressor, and plays a vital role in the stability of the compressor's operation, compression effect and service life. At present, the exhaust valve plates on air compressors are basically made of stainless steel, aluminum-based alloy, polyurethane, tetrafluoroethylene, etc. These materials play different roles in different working conditions.

[0003] Polyetheretherketone (PEEK) is a special engineering plastic. It is widely studied and used to manufacture valve plates for compressor valves due to its excellent physical, chemical and mechanical properties. It has many advantages that metal materials cannot match:

[0004] (1) High temperature resistance: The long-term operating temperature of fiber-reinforced PEEK can reach 260°C; (2) Wear resistance: Due to its low density and light weight, the impact force in the reciprocating compressor is reduced, which extends the life of the valve; (3) Corrosion resistance: Except for oxygen, chlorine and concentrated sulfuric acid, PEEK is resistant to corrosion from almost all media, especially fluorine-containing PEEK composite materials have outstanding corrosion resistance; (4) Low noise: PEEK material can absorb part of the impact energy and reduce noise; (5) High safety: PEEK valve plates have good toughness and are not easy to break. Even if they break, they will not cause damage to the valve or generate sparks; (6) Hydrolysis resistance: They are not affected by water and high-pressure steam and maintain mechanical properties.

[0005] Despite this, under special working conditions such as strong acids and alkalis, PEEK is inevitably caught in a dilemma between strength and corrosion resistance: fluorine-containing PEEK composites have poor mechanical properties, and conventional inorganic filler-reinforced PEEK composites are difficult to withstand corrosion, which makes it increasingly difficult for single-ratio PEEK composites to meet the performance requirements of valve materials under special working conditions.

[0006] In view of the above situation, the present application designs a layer structure realized by a secondary injection molding process, and a series of PEEK composite materials matched therewith, so as to meet the performance requirements of PEEK valve plates under acid and alkali corrosion conditions. Summary of the invention

[0007] The purpose of the present invention is to solve the problems in the prior art and to provide a method for preparing a layered PEEK composite material used for compressor valve plates. The purpose is to provide a compressor exhaust valve plate material and its preparation process that have both mechanical strength and corrosion resistance. PEEK is used as the base resin, and an inner layer structural material with high mechanical strength and an outer layer structural material with excellent corrosion resistance are prepared through composite modification. The layer structure is obtained through a secondary injection molding process, so that the product has excellent corrosion resistance while maintaining the high strength characteristics of PEEK.

[0008] The present invention achieves the above-mentioned purpose through the following technical scheme: a method for preparing a layered PEEK composite material used for a compressor valve plate, comprising the following steps:

[0009] S1 Preparation of inner layer structure PEEK composite material: The inner layer structure PEEK composite material components include PEEK resin, a first filler, a release agent, and a dispersant, wherein the PEEK resin accounts for 50-80% of the total mass of the composite material, the first filler is a fiber filler and a ceramic filler, and the total amount of the release agent and the dispersant is less than 1% of the total mass of the inner layer structure PEEK composite material;

[0010] S2 Preparation of outer layer structure PEEK composite material: The outer layer structure PEEK composite material components include PEEK resin, a second filler, a release agent, and a dispersant. The PEEK resin accounts for 50-70% of the total mass of the composite material. The second filler is fluoroplastic. The total amount of the release agent and the dispersant is less than 1% of the total mass of the outer layer structure PEEK composite material.

[0011] S3 secondary injection molding: First, the inner layer structure PEEK composite material is injected into the mold to initially form the inner layer structure. The parts after the first injection molding are taken out, cleaned and surface treated, and then fixed in the mold for the second injection molding. The outer layer structure PEEK composite material is injected into the mold for the second molding and covers the inner layer structure. The parts after injection molding are heat treated to eliminate internal stress, and the redundant positioning structure and flash defects are removed by mechanical processing.

[0012] Preferably, the fiber filler is one of carbon fiber and glass fiber, and the ceramic filler is one or both of zirconium dioxide and titanium dioxide.

[0013] Preferably, the fluoroplastic is one or both of polytetrafluoroethylene (PTFE) and perfluoroalkyl (PFA), and the content of polytetrafluoroethylene is not more than 30% of the total mass of the outer layer structure PEEK composite material.

[0014] Preferably, the surface treatment after the first injection molding is sandblasting roughening.

[0015] Preferably, during the second injection molding process, the mold temperature is 180°C-200°C and the injection temperature is 380°C-420°C.

[0016] Preferably, in step S3, after the inner layer structure is formed, it has a plurality of protrusions on both sides, and the protrusions play a positioning role when the outer layer structure is formed, and after the outer layer structure is formed, the protrusions are trimmed to make them flush with the surface of the outer layer structure.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The outer structure provides anti-corrosion protection for the valve plate, and the inner structure provides good mechanical properties for the valve plate;

[0019] 2. Both the inner and outer materials are PEEK composite materials with the same melting temperature, which can make the interface fusion more complete during the processing and molding process, and reduce the structural defects between the valve layers;

[0020] 3. Through the sandblasting roughening process, the interlayer bonding force is further strengthened. At the same time, during the secondary injection molding, the molten outer layer material can also repair the structural defects caused by sandblasting in the process of fusion with the inner layer structure;

[0021] 4. The mold temperature during the second injection molding is controlled within the cold crystallization temperature range of PEEK, which can further improve the crystallinity of the inner layer structure, enhance the strength, and reduce the internal stress between layers;

[0022] 5. Compared with fluorine-containing PEEK composites, fiber-reinforced PEEK composites have lower thermal expansion coefficients and molding shrinkage rates, but the thermal expansion coefficients and molding shrinkage rates of ceramic powder-reinforced PEEK composites are similar to those of fluorine-containing PEEK composites. The compounding of multiple fillers can further reduce interlaminar stress. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of a method for preparing a layered PEEK composite material used for a compressor valve plate of the present invention;

[0024] Figure 2 This is a schematic diagram of the structure of the compressor valve plate of the present invention;

[0025] Figure numerals: 1, inner layer structure; 2, outer layer structure; 3, convex column. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] like Figure 1-Figure 2 As shown, a method for preparing a layered PEEK composite material for a compressor valve plate comprises the following steps:

[0028] S1 Preparation of inner layer structure 1 PEEK composite material: The components of the inner layer structure 1 PEEK composite material include PEEK resin, a first filler, a release agent, and a dispersant, wherein the PEEK resin accounts for 50-80% of the total mass of the composite material, the first filler is a fiber filler and a ceramic filler, and the total amount of the release agent and the dispersant is less than 1% of the total mass of the inner layer structure 1 PEEK composite material, wherein the fiber filler is one of carbon fiber and glass fiber, and the ceramic filler is one or both of zirconium dioxide and titanium dioxide;

[0029] S2 Preparation of outer layer structure 2PEEK composite material: The outer layer structure 2PEEK composite material components include PEEK resin, second filler, release agent, and dispersant. PEEK resin accounts for 50-70% of the total mass of the composite material. The second filler is fluoroplastic. The total amount of release agent and dispersant is less than 1% of the total mass of the outer layer structure 2PEEK composite material. The fluoroplastic is one or two of polytetrafluoroethylene (PTFE) and perfluoroalkyl compound (PFA), and the content of polytetrafluoroethylene is not more than 30% of the total mass of the outer layer structure 2PEEK composite material.

[0030] S3 secondary injection molding: first, the inner layer structure 1 PEEK composite material is injected into the mold to preliminarily form the inner layer structure 1, and the parts after the first injection molding are taken out. At the same time, the surface treatment after the first injection molding is sandblasting roughening. After the inner layer structure 1 is formed, it has a number of protrusions 3 on both sides, and the protrusions 3 play a positioning role when the outer layer structure 2 is formed. After the outer layer structure 2 is formed, the protrusions 3 are trimmed to make them flush with the surface of the outer layer structure. Then, after cleaning and surface treatment, they are fixed in the mold for the second injection molding, and the outer layer structure 2 PEEK composite material is injected into the mold for the second molding, covering the inner layer structure 1. The parts after injection molding are subjected to heat treatment to eliminate internal stress, and the redundant positioning structure and flash defects are removed by mechanical processing. During the second injection molding process, the mold temperature is 180℃-200℃, and the injection temperature is 380℃-420℃.

[0031] In the traditional method, the preparation of valve plates generally relies on one-time injection molding of the main material, and electrostatically spraying polytetrafluoroethylene on the surface of the main material in the form of powder, and then melting it by heating to form a protective film on the surface of the main material. However, the valve plates made by this method have poor adhesion between polytetrafluoroethylene PTFE and the main material, resulting in a short service life and poor corrosion resistance.

[0032] The valve plate of the present invention is prepared by a secondary injection molding method. The inner layer structure 1 is mainly composed of PEEK resin, fiber fillers and ceramic fillers, which have good impact resistance and wear resistance, and the outer layer structure 2 is mainly composed of PEEK resin and fluoroplastics, which have good corrosion resistance. In the specific molding process, the inner layer structure 1 is placed in a secondary injection mold after the primary injection molding, wherein the convex column 3 on the surface of the inner layer structure 1 can not only play a positioning effect during the secondary injection molding, but also the convex column 3 is finally flush with the surface of the outer layer structure 2, so that the valve plate conflicts with the installation position of the spring in the air valve, which can provide a better wear-resistant support effect on the spring, and Since both the inner layer structure 1 and the outer layer structure 2 contain PEEK resin, the contact surfaces of the inner layer structure 1 and the outer layer structure 2 can be fused during the secondary injection molding, so that the inner layer structure 1 and the outer layer structure 2 have better adhesion and are not easy to fall off. In addition, after the inner layer structure 1 is molded, sandblasting and roughening will be performed on its surface. During the sandblasting process, the gravel will impact the surface of the inner layer structure 1 to increase the roughness of the surface of the inner layer structure 1, so that the bonding force between the inner layer structure 1 and the outer layer structure 2 can be further increased during the secondary injection molding. At the same time, the fine cracks produced in the inner layer structure 1 after sandblasting and roughening can be repaired during the secondary injection molding, which can reduce the defects of the inner layer structure 1.

[0033] At the same time, since the inner layer structure 1 and the outer layer structure 2 are formed by secondary injection molding, and there are differences in the materials of the two, resulting in different thermal expansion coefficients, in order to ensure the quality of valve plate production, it is necessary to control the thermal expansion coefficients of the inner layer structure 1 material and the outer layer structure 2 material as close as possible, so as to effectively avoid surface cracking when molding the outer layer structure 2. In the material of the inner layer structure 1, the thermal expansion coefficient of the PEEK resin is low after only adding fiber fillers, while the thermal expansion coefficient of the PEEK resin in the material of the outer layer structure 2 is high after adding fluoroplastics. Therefore, it is necessary to add ceramic fillers to the material of the inner layer structure 1, so that the reduction in the thermal expansion coefficient of the fiber filler is reduced, so as to prevent damage caused by stress between layers during the molding and heating process. At the same time, the ceramic filler also enriches the inner layer structure 1, so that the impact resistance of the inner layer structure 1 is significantly improved.

[0034] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0035] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for preparing a layered PEEK composite material for a compressor valve plate, characterized in that: The following steps are involved: S1 Preparation of inner layer structure (1) PEEK composite material: The inner layer structure (1) PEEK composite material components include PEEK resin, a first filler, a release agent, and a dispersant, wherein the PEEK resin accounts for 50-80% of the total mass of the composite material, the first filler is a fiber filler and a ceramic filler, and the total amount of the release agent and the dispersant is less than 1% of the total mass of the inner layer structure (1) PEEK composite material; S2 Preparation of outer layer structure (2) PEEK composite material: The outer layer structure (2) PEEK composite material components include PEEK resin, a second filler, a release agent, and a dispersant, wherein the PEEK resin accounts for 50-70% of the total mass of the composite material, the second filler is a fluoroplastic, and the total amount of the release agent and the dispersant is less than 1% of the total mass of the outer layer structure (2) PEEK composite material; S3 secondary injection molding: First, the inner layer structure (1) PEEK composite material is injected into the mold to initially form the inner layer structure (1). The parts after the first injection molding are taken out, cleaned and surface treated, and then fixed in the mold for the second injection molding. The outer layer structure (2) PEEK composite material is injected into the mold for the second molding and covers the inner layer structure (1). The parts after injection molding are subjected to heat treatment to eliminate internal stress, and the redundant positioning structure and flash defects are removed by mechanical processing.

2. The method for preparing a layered PEEK composite material for compressor valve plates according to claim 1, characterized in that: The fiber filler is one of carbon fiber and glass fiber, and the ceramic filler is one or both of zirconium dioxide and titanium dioxide.

3. The method for preparing a layered PEEK composite material for compressor valve plates according to claim 1, characterized in that: The fluoroplastic is one or both of polytetrafluoroethylene (PTFE) and perfluoroalkyl (PFA), and the content of polytetrafluoroethylene is not greater than 30% of the total mass of the PEEK composite material of the outer layer structure (2).

4. The method for preparing a layered PEEK composite material for compressor valve plates according to claim 1, characterized in that: The surface treatment after the first injection molding is sandblasting roughening.

5. The method for preparing a layered PEEK composite material for compressor valve plates according to claim 1, characterized in that: During the second injection molding process, the mold temperature is 180°C-200°C, and the injection molding temperature is 380°C-420°C.

6. The method for preparing a layered PEEK composite material for compressor valve plates according to claim 1, characterized in that: In step S3, after the inner layer structure (1) is formed, it has a plurality of convex columns (3) on both sides, and the convex columns (3) play a positioning role when the outer layer structure (2) is formed. After the outer layer structure (2) is formed, the convex columns (3) are trimmed to make the surface of the outer layer structure (2) flush.

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