Thermosetting resin-based composite material remodeling and recycling process based on hot pressing technology

Abstract

The invention relates to the technical field of composite material recovery and remodeling, in particular to a thermosetting resin based composite material remodeling recovery process based on a hot pressing technology. According to the specific technical scheme, the method comprises the following steps: (1) placing the waste composite material in a mold, and heating the composite material to soften resin; (2) applying pressure to change the shape of the composite material and reshape the composite material to reach a preset size or form; (3) keeping the heating temperature and pressure to ensure that the resin is uniformly softened and flows; and (4) the composite material is remodeled when the temperature is lower than the glass-transition temperature through cooling, and the composite material with the needed shape and performance is finally obtained. The problems that in the prior art, the composite material recycling efficiency is low, the mechanical property of fibers is reduced in the recycling process, environment pollution is caused, energy consumption is high, and the cost is high are solved.

Description

Technical Field

[0001] The invention relates to the technical field of composite material recycling and reshaping, and in particular to a thermosetting resin-based composite material reshaping recycling process based on hot pressing technology. Background Art

[0002] With the widespread application of composite materials in high-tech fields such as wind power, aerospace, automobiles, and construction, composite materials have become more and more popular due to their light weight, high strength, and excellent corrosion resistance. However, the recycling of composite materials, especially thermosetting reinforced resin-based composite materials, has always been the focus of attention in the industry. Due to the complexity of composite materials (such as the close combination of resin and reinforcing fiber), traditional recycling methods often face great technical challenges.

[0003] At present, the recycling technology of composite materials mainly includes the following methods:

[0004] Mechanical pulverization: Cutting and crushing the discarded composite materials into smaller particles by mechanical means is suitable for processing some large-sized waste materials. However, this method cannot effectively separate the resin and reinforcing fibers, and the pulverization process may cause the fibers to shorten, reducing the quality of the recycled materials.

[0005] Pyrolysis: The pyrolysis method uses high temperature to decompose the resin into gas or liquid, and the remaining solid is fiber. Although this method can effectively separate the resin and fiber, there are still resin residues on the fiber, and it has high energy consumption and complicated operation. Harmful gases may be generated during the treatment process, causing environmental pollution. In addition, the pyrolysis process has a certain impact on the physical properties of the recycled fiber, and the strength of the recycled fiber may decrease.

[0006] Solvent method: Solvent is used to dissolve the resin and separate the reinforcing fiber from the resin. Although this method can separate the resin and fiber well, the solvent used is often polluting the environment, and the recovery and treatment of the solvent is a complicated and expensive process.

[0007] Mechanical and chemical combination method: Combine mechanical and chemical methods to recycle composite materials, first mechanically crushing and then further separating them using solvents or pyrolysis. Although this method can improve the recovery rate, it is complicated to operate and has high costs.

[0008] Although these recycling methods have solved the recycling problem of composite materials to a certain extent, there are still problems such as low recycling efficiency, poor quality of recycled fibers, and environmental pollution. Therefore, how to improve the recycling efficiency of composite materials, reduce costs, and maintain the mechanical properties of fibers during the recycling process has become a technical problem that needs to be solved urgently in the current field of composite material recycling. Summary of the invention

[0009] In view of the shortcomings of the prior art, the present invention provides a thermosetting resin-based composite material reshaping and recycling process based on hot pressing technology, which solves the problems of low composite material recycling efficiency, decreased mechanical properties of fibers during the recycling process, environmental pollution, high energy consumption, and high costs in the prior art.

[0010] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0011] The present invention discloses a thermosetting resin-based composite material reshaping and recycling process based on hot pressing technology, comprising the following steps:

[0012] (1) placing the waste composite material in a mold and heating the composite material to soften the resin;

[0013] (2) applying pressure to cause the composite material to change shape and reshape to a predetermined size or shape;

[0014] (3) Maintaining the heating temperature and pressure to ensure uniform softening and flow of the resin, improve the geometric shape stability of the composite material after reshaping, and ensure the overall mechanical properties of the composite material;

[0015] (4) By cooling, the composite material is reshaped below the glass transition temperature, and finally a composite material with the desired morphology and properties is obtained.

[0016] Preferably, in step (1), the resin is softened at a temperature of 120 to 160°C.

[0017] Preferably, in step (2), the applied pressure is at least 100 kPa, and the pressure is maintained for at least 120 minutes.

[0018] Preferably, in step (1), the composite material is sealed by a vacuum bag.

[0019] Preferably, the reinforcing fibers of the composite material are glass fibers or carbon fibers.

[0020] Preferably, the upper and lower surfaces of the composite material are wrapped with release cloth.

[0021] Preferably, the upper surface of the composite material is covered with air-permeable felt.

[0022] Preferably, the mold is a steel mold.

[0023] The present invention has the following beneficial effects:

[0024] 1. The present invention directly performs orthopedic treatment on the discarded composite material by heating and pressurizing without separating the resin and the reinforcing fiber, so that the composite material can be restored to its original shape or reshaped into a new high-performance structure, thereby realizing the reuse of the material and completing the recycling process under low energy consumption and high efficiency conditions. Moreover, this method can not only avoid the separation process of resin and fiber in traditional recycling technology and reduce material loss, but also greatly improve the recycling efficiency, reduce costs, and reduce environmental pollution.

[0025] 2. The present invention enables the composite material to undergo morphological changes at a lower temperature through precise temperature and pressure control, thus avoiding excessive decomposition of the resin or fiber damage, and not affecting the mechanical properties of the reinforcing fibers. Compared with traditional recycling methods, this method can better preserve the physical properties of the material, thereby improving the quality of the recycled material and ensuring that it can be directly used in subsequent manufacturing and production.

[0026] 3. Unlike pyrolysis or chemical solvent recovery technology, the technology of the present invention does not require excessively high temperature treatment or harmful solvents, but achieves the reshaping of composite materials through simple physical methods of heating and pressurization. This technology has the characteristics of low energy consumption and no pollution, which meets the current needs of green environmental protection and sustainable development.

[0027] 4. The present invention uses this heating and pressurizing reshaping technology to enable composite materials to change their shape quickly while ensuring quality, greatly reducing energy consumption and equipment investment in the recycling process, and improving the economic recycling value of composite materials. Compared with other high-energy consumption and high-cost recycling methods, the technology of the present invention can significantly reduce the cost of industrial waste treatment and achieve more efficient material reuse.

[0028] 5. The technology of the present invention is not only applicable to the currently widely used glass fiber reinforced composite materials, but can also be extended to the recycling and reuse of high-performance composite materials such as carbon fiber composite materials. The application areas cover the recycling of waste composite materials in industries such as wind power, aerospace, automobiles, and construction, which can not only reduce environmental pollution, but also save a lot of waste treatment costs for enterprises. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of vacuum infusion molding technology;

[0030] Figure 2 This is a schematic diagram of the hot pressing reshaping technology;

[0031] Figure 3 for Figure 2 The view in the middle ellipse;

[0032] Figure 4 This is the setting diagram for the autoclave process. DETAILED DESCRIPTION

[0033] 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.

[0034] Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0035] The present invention discloses a thermosetting resin-based composite material reshaping and recycling process based on hot pressing technology, comprising the following steps:

[0036] (1) placing a waste composite material in a mold, wherein the composite material is a resin-based composite material, comprising reinforcing fibers and a curing resin, and preferably, the reinforcing fibers of the composite material are glass fibers or carbon fibers; heating the composite material to soften the resin; the temperature at which the resin softens is 120 to 160° C. The mold is a steel mold with good flatness and high temperature resistance.

[0037] (2) applying pressure to cause the composite material to change shape and reshape to a predetermined size or shape; the applied pressure is at least 100 kPa and the pressure is maintained for at least 120 minutes.

[0038] (3) Maintaining the heating temperature and pressure can improve the geometric stability of the composite material after reshaping, while ensuring that the resin can soften evenly and fill the voids in the composite material, so that the bonding interaction between the resin and the composite material can be fully developed, thereby ensuring the overall mechanical properties of the composite material.

[0039] (4) By cooling, the composite material is reshaped below the glass transition temperature, and finally a composite material with the desired morphology and properties is obtained.

[0040] Furthermore, during the heating and pressurizing process, the composite material is sealed by a vacuum bag to ensure uniform heating and pressurizing of the composite material and reduce spillage of the resin.

[0041] Furthermore, the upper and lower surfaces of the composite material are wrapped with release cloth. After the release cloth is wrapped, the upper surface of the composite material is covered with breathable felt to form an air channel. Then the vacuum bag is tightly covered on the composite material with sealant. Finally, the vacuum bag is evacuated by a vacuum pump until the vacuum degree is stabilized at a vacuum state of more than 90%, ensuring that the resin part of the composite material does not overflow during the whole process and the reinforcing fiber is always in a stable state. Finally, the heating and pressurization process is carried out.

[0042] Example 1: Composite material recycling and reshaping method

[0043] Raw material preparation: In order to explore the molding effect of the recycling process, GFRP (Glass Fiber Reinforced Polymer) with different curvatures were prepared as the specimens to be recycled. The specific preparation process is as follows ( Figure 1 ): Preparation stage (designing and processing molds, preparing raw materials such as fiberglass cloth, epoxy resin and vacuum-assisted media), laying stage (laying raw materials such as fiberglass cloth, epoxy resin and release cloth, guide net and other related media on the mold), sealing stage (vacuuming to ensure airtightness), infusion stage (infusing resin under vacuum and impregnating reinforcing materials), curing stage (maintaining vacuum and curing the resin to form a preform), post-processing stage (cleaning molds and media, and trimming products).

[0044] Specific as Figure 1 As shown in the figure, vacuum infusion molding technology includes a mold: the mold is used to fix and shape the material to be infused. Its internal shape and size determine the appearance of the final product, and the mold material has high thermal conductivity and can effectively disperse the heat during the molding process.

[0045] Vacuum chamber: A vacuum chamber is set outside the mold to create the necessary low-pressure environment to ensure that bubbles are effectively removed during the infusion process. At the same time, a guide net is set inside the vacuum chamber to assist the resin to evenly penetrate every detail of the mold. In addition, there are multiple vacuum chambers to make test pieces with different curvatures to verify the remodeling recycling process.

[0046] Pipeline system: connects the injection port with the external resin supply system to ensure the continuous flow of injection resin.

[0047] Resin supply system: The external resin barrel is responsible for providing the required raw materials and delivering them into the vacuum chamber through a pipeline system (such as a rubber inlet hose). This system is usually directly connected to the infusion port and can adjust the flow rate and flow rate as needed to ensure that the resin flows fully throughout the molding process.

[0048] Vacuum pump: By setting up the rubber outlet hose and vacuum pump, it is responsible for extracting the air in the vacuum chamber to form a negative pressure environment. The vacuum pump is a key component to maintain molding accuracy and remove bubbles. By adjusting the vacuum pump's exhaust rate, the pressure in the vacuum chamber can be controlled to ensure that the infusion material flows under optimal conditions and at the same time, the excess resin is extracted.

[0049] The flow chart of the autoclave hot pressing process is as follows Figure 2 , Figure 3 The specific process is as follows:

[0050] Mold material: steel mold is used as the mold under the specimen reshaping to ensure that its surface is flat and has strong high temperature resistance. It can remain stable under high pressure and high temperature conditions and is not easy to deform. The excellent performance of the steel mold helps to evenly transfer heat and pressure during the reshaping process to ensure the molding effect of the specimen.

[0051] Insertion of waste composite materials: Place the test specimens prepared above as waste composite materials in the mold. Place the test specimen accurately in the center of the mold. Considering that the resin will enter a viscous flow state during the heating process, to prevent the test specimen from sticking to the mold, use a release cloth to wrap the upper and lower surfaces of the test specimen. The use of release cloth helps to ensure the separation of the test specimen from the mold and prevent adhesion. The selection of release cloth requires good high temperature resistance and air permeability so as not to affect the shape change of the composite material during the subsequent heating and pressurization process.

[0052] The test piece is covered with a breathable felt to form an air passage, that is, to form an air passage covering all parts of the test piece, so that a uniform vacuuming effect can be achieved when the vacuum pump is used to draw a vacuum. At the same time, the breathable felt can absorb the resin that may overflow during the heating process to prevent the resin from leaking out.

[0053] Vacuum sealing and vacuuming: After placing the composite material into the mold, use a vacuum bag to completely cover it, and use sealant to ensure the sealing of the vacuum bag and the mold, that is, use sealant to tightly cover the vacuum bag on the top of the test piece. After sealing, use a vacuum pump to extract the air in the bag to form a vacuum environment. Specifically: In order to ensure stability during the hot pressing process, the vacuum degree in the vacuum bag is stabilized at a vacuum state of more than 90%, so as to ensure that the resin is fully impregnated and achieve the best molding effect, and ensure that the resin part of the composite material does not overflow during the entire process, and the reinforcing fiber is always in a stable state.

[0054] Heating stage: Set up the heating system to heat the mold to the set temperature. The heating temperature range is set between 120 and 160°C, and the specific temperature is adjusted according to the resin type of the composite material and its glass transition temperature. Generally speaking, it needs to be 20 to 30°C higher than the glass transition temperature. During the heating process, the temperature control system is used to accurately control the heating temperature to ensure the softening and fluidity of the resin, but it will not cause excessive flow and uneven distribution of the resin after re-curing. Specific: such as Figure 4 As shown in the figure, in the heating stage, the time required from the start of heating to the set temperature (such as 120°C) shows a linear or nearly linear upward trend. In this stage, the composite material in the mold is gradually heated to the predetermined temperature at a constant heating rate (such as 10°C / min).

[0055] Pressurization stage: When the composite material is about to reach the predetermined temperature, the system automatically applies pressure to make the autoclave reach the predetermined temperature and pressure at the same time. The pressure value is set according to the actual specimen to be recycled to ensure that the resin can flow evenly between the reinforcing fibers in a softened state, while maintaining the overall structure of the specimen to undergo plastic deformation. The pressurization rate is set to 100kPa / min, and a certain pressure is maintained during the constant pressure stage. The time is generally set to 120 minutes to ensure that the specimen to be recycled has undergone sufficient plastic deformation and achieved a high degree of flatness.

[0056] Constant temperature and pressure maintenance: During the pressurization process, the temperature of the heating system continues to be kept stable and maintained within the preset range. Figure 4 As shown, the curve remains stable at this stage, and the constant temperature and pressure are usually maintained for 120 minutes to ensure that the specimen to be recycled has undergone sufficient plastic deformation and has achieved a high degree of flatness. During this period, the temperature and pressure will not fluctuate violently to ensure that the resin material can soften evenly and fill the voids of the composite material, and the bonding interaction between the resin material and the composite material can be fully developed, thereby ensuring the overall mechanical properties of the composite material. During this process, the system monitors the temperature changes in the mold, uses thermocouples or temperature sensors to provide real-time feedback, and adjusts the heating system to ensure temperature stability.

[0057] Cooling stage: After the constant temperature and pressure treatment is completed, the temperature gradually decreases and the cooling process begins. Figure 4 As shown, the curve shows a downward trend at this stage, and the cooling rate is controlled within the set range to avoid deformation or cracks of the composite material due to rapid cooling. Cooling adopts natural air cooling, and the temperature in the mold is reduced by fans and other devices. During the cooling process, it is ensured that the composite material maintains structural stability without rebound or deformation. When it is cooled below the glass transition temperature, the mold can be removed to complete the reshaping process of the composite material.

[0058] Removal and post-processing: After cooling, the composite material is removed from the mold, and the demoulding cloth and vacuum bag can be safely removed. At this point, the composite material has changed its morphology and has sufficient mechanical properties for subsequent applications. Perform an appearance inspection on the removed composite material to ensure that its surface is flat and has no obvious defects.

[0059] Composite material performance test: The performance test of the recycled composite material mainly includes two indicators: curvature change and tensile strength. The test results show that the curvature change of the recycled composite material exceeds 50%. Some small curvature specimens are completely flat after reshaping and can be put into use as flat plates and other structural forms. Its tensile strength is still close to the level of raw materials, and its performance is stable, which can meet the requirements of industrial applications.

[0060] Example 2 Multiple remodeling processes of composite materials

[0061] Waste composite materials: Common thermosetting resin-based composite materials in the aviation industry are selected, with carbon fiber as the reinforcing material and epoxy resin as the resin type. The material is in the state of waste and has been used for a certain period of time, with certain damage and deformation on the surface.

[0062] Multiple heating and pressurizing treatments: The composite material recovered for the first time is subjected to heating and pressurizing treatments again. The temperature and pressure of each treatment are set the same as those in Example 1 and maintained for 120 minutes. Repeating this process can gradually release the residual stress generated by the material during the heating and pressurizing process, which is conducive to maintaining the stability of the structural shape after the reshaping is completed.

[0063] Cooling and performance recovery: After multiple reshaping, the mechanical properties of the composite material are close to those of the composite material used for the first time, and there is no obvious thermal damage or structural failure on its surface.

[0064] It can be seen from Examples 1 and 2 that the composite material recycling and reshaping method of the present invention can efficiently restore the performance of waste composite materials, is easy to operate, and is applicable to different types of resin-based composite materials. It has significant advantages in environmental protection, resource recycling, and industrial cost control, and provides an effective solution for the recycling of composite materials.

[0065] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A thermosetting resin-based composite material reshaping and recycling process based on hot pressing technology, characterized in that: The following steps are involved: (1) placing the waste composite material in a mold and heating the composite material to soften the resin; (2) applying pressure to cause the composite material to change shape and reshape to a predetermined size or shape; (3) Maintain heating temperature and pressure to ensure that the resin softens and flows evenly; (4) By cooling, the composite material is reshaped below the glass transition temperature, and finally a composite material with the desired morphology and properties is obtained.

2. The thermosetting resin-based composite material reshaping and recycling process based on hot pressing technology according to claim 1 is characterized in that: In step (1), the resin is softened at a temperature of 120 to 160°C.

3. The thermosetting resin-based composite material reshaping and recycling process based on hot pressing technology according to claim 1 is characterized by: In step (2), the applied pressure is at least 100 kPa, and the pressure is maintained for at least 120 minutes.

4. The thermosetting resin-based composite material reshaping and recycling process based on hot pressing technology according to claim 1 is characterized in that: In step (1), the composite material is sealed by a vacuum bag.

5. The thermosetting resin-based composite material reshaping and recycling process based on hot pressing technology according to claim 1, characterized in that: The reinforcing fibers of the composite material are glass fibers or carbon fibers.

6. The thermosetting resin-based composite material reshaping and recycling process based on hot pressing technology according to claim 4 is characterized in that: The upper and lower surfaces of the composite material are wrapped with release cloth.

7. The thermosetting resin-based composite material reshaping and recycling process based on hot pressing technology according to claim 6 is characterized by: The upper surface of the composite material is covered with air-permeable felt.

8. The thermosetting resin-based composite material reshaping and recycling process based on hot pressing technology according to claim 1, characterized in that: The mould is a steel mould.

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