Method for preparing carbon fiber sizing agent by using waste PMI foam and application

Abstract

This invention belongs to the field of waste polymer material recycling and carbon fiber surface treatment technology, specifically relating to a method and application of preparing a carbon fiber sizing agent using waste PMI foam. To achieve high-value closed-loop utilization of waste PMI foam and improve the interfacial bonding performance between carbon fiber and the resin matrix, this invention pre-treats the waste PMI foam and then catalytically degrades it in a strong alkaline aqueous solution to obtain a resin degradation liquid. The resin degradation liquid is then mixed and emulsified with a compound resin, an antistatic agent, a diluent, and an emulsifier to obtain a carbon fiber sizing agent. The carbon fiber is then impregnated with this sizing agent, acidified, washed, and dried to obtain sized carbon fiber, which is then composited and cured with a resin matrix to obtain a carbon fiber composite material.

Description

Technical Field

[0001] This invention belongs to the field of waste polymer material recycling and carbon fiber surface treatment technology, specifically involving a method for preparing carbon fiber sizing agent using waste polymethacrylimide (PMI) foam, the application of the sizing agent in the preparation of carbon fiber composite materials, and the preparation method of carbon fiber composite materials. Background Technology

[0002] Polymethacrylimide (PMI) foam is a lightweight, high-strength, and high-temperature resistant rigid foam material widely used in high-end fields such as aerospace, new energy vehicles, and rail transportation. It is primarily used as the core material in sandwich structures of carbon fiber composites, playing an irreplaceable role in aircraft fuselages, wings, and radar communication equipment. With the rapid development of these fields, the usage of PMI foam has increased year by year, resulting in a significant increase in waste PMI foam (such as processing scraps and end-of-life products). Due to the high-temperature resistance and non-degradability of PMI foam, its recycling currently mainly focuses on physical crushing to produce low-value-added products or incineration for energy recovery. This not only wastes resources but also may produce harmful gases and pollute the environment during incineration. While chemical recycling can achieve high-value recycling, current technologies mostly focus on decomposing it into small-molecule monomers, failing to achieve efficient linkage with the carbon fiber industry, and resource utilization still needs improvement.

[0003] Carbon fiber, as the core reinforcement in high-performance composite materials, suffers from low surface chemical activity and insufficient interfacial compatibility with the resin matrix, severely limiting the improvement of the overall mechanical properties of the composite material. Therefore, sizing treatment is necessary to improve its surface properties, enhance the interfacial bonding strength with the resin matrix, and achieve effective load transfer. Currently, most commercially available carbon fiber sizing agents are prepared using newly synthesized resin raw materials, resulting in high production costs and reliance on imported raw materials. Furthermore, existing sizing agents lack integration with the PMI foam recycling system, failing to achieve synergistic recycling of waste polymer materials and the carbon fiber industry, which does not meet the requirements of green and low-carbon development. Simultaneously, in the current carbon fiber composite material preparation process, the compatibility between the sizing agent and the resin matrix is ​​insufficient, easily leading to problems such as interfacial delamination and unstable mechanical properties.

[0004] Therefore, developing a method for preparing carbon fiber sizing agents using waste PMI foam, directly converting the chemically recycled products of waste PMI foam into effective components of carbon fiber sizing agents, can not only achieve high-value recycling of waste, but also improve the interfacial bonding performance between carbon fiber and resin matrix, and reduce the production cost of sizing agents. This is of great significance for promoting the green and sustainable development of the carbon fiber composite materials industry. Summary of the Invention

[0005] This invention provides a method and application for preparing carbon fiber sizing agents using waste PMI foam, in order to solve the following technical problems:

[0006] (1) The problem of low recycling rate and lack of high-value utilization of waste PMI foam. Existing technologies mostly use physical crushing or incineration, which makes it difficult to achieve high-value recycling of waste PMI foam. Moreover, the incineration process easily produces harmful gases and pollutes the environment. Chemical recycling technology mainly focuses on decomposition into small molecule monomers and has not yet formed an effective linkage with the carbon fiber industry.

[0007] (2) The problem of high production cost and reliance on imported raw materials for carbon fiber sizing agents. Currently, most commercially available carbon fiber sizing agents use newly synthesized resin raw materials, which have high preparation costs, and some key raw materials need to be imported, which restricts the low-cost development of carbon fiber composite materials.

[0008] (3) Problem of insufficient interfacial bonding performance between carbon fiber and resin matrix. The surface chemical activity of carbon fiber is low, and the compatibility of existing sizing agents with different resin matrices is poor, which can easily lead to interfacial delamination of composite materials, unstable mechanical properties, and affect the overall load-bearing capacity.

[0009] (4) There is a lack of synergistic circulation between the two major technical fields of waste polymer material recycling and carbon fiber surface treatment. A closed-loop technical path from waste PMI foam to carbon fiber sizing agent and then to composite material preparation has not yet been formed, which does not meet the needs of green and low-carbon development.

[0010] To achieve the above objectives, the present invention employs the following technical solution:

[0011] In a first aspect, the present invention provides a method for preparing a carbon fiber sizing agent using waste PMI foam, comprising the following steps:

[0012] (1) Collect waste PMI foam and pretreat it to obtain PMI foam fragments; add the PMI foam fragments to the catalytic degradation system to carry out the degradation reaction, heat up to the degradation reaction temperature, react until PMI is completely degraded, cool to room temperature to obtain resin degradation liquid, and then obtain PMI foam degradation resin.

[0013] (2) The PMI foam degradation resin obtained in step (1) is mixed with compound resin, antistatic agent and diluent in a certain mass ratio, and then an emulsifier is added for emulsification treatment until a uniform and transparent emulsion solution is formed. The insoluble matter is removed by filtration to obtain carbon fiber sizing agent.

[0014] Furthermore, the pretreatment in step (1) includes removing impurities and washing, drying, and crushing into fragments. The drying temperature is 80-100℃, the drying time is 2-4 hours, and the fragment size is 1-60cm. 2 ;

[0015] The catalytic degradation system is a strong alkaline aqueous solution, where the strong alkaline is sodium hydroxide, potassium hydroxide, or lithium hydroxide, with a concentration of 1-30 wt%. The ratio of PMI foam fragments to the strong alkaline aqueous solution is 100 g: 300-600 mL.

[0016] The degradation reaction temperature is 100-260℃, and the degradation reaction time is 2-24h.

[0017] Furthermore, in step (2), the mass ratio of PMI foam degradation resin, compound resin, antistatic agent, diluent and emulsifier is 100:(5-15):(0.1-1.0):(200-400):(0.5-2.0);

[0018] The compounded resin is a thermoplastic resin or a thermosetting resin;

[0019] The antistatic agent is polyvinyl alcohol, ethylene glycol methacrylate copolymer or polyether ester amide;

[0020] The diluent is one or a mixture of two of acetone, ethanol, and deionized water;

[0021] The emulsifier is one or a mixture of two of the following: polyoxyethylene, sorbitan fatty acid ester (Tween-80), and sodium dodecylbenzene sulfonate (SDBS).

[0022] Furthermore, the thermoplastic resin is selected from polyamide resin and polyvinyl alcohol resin, and the thermosetting resin is selected from epoxy resin and unsaturated polyester resin.

[0023] Furthermore, in step (2), the rotation speed of the emulsification process is 1000-2000 r / min, and the time is 15-30 min; the solid content of the sizing agent obtained after emulsification is controlled at 10%-60%.

[0024] In a second aspect, the present invention provides a carbon fiber sizing agent, which is prepared by the method described in the first aspect of preparing a carbon fiber sizing agent using waste PMI foam.

[0025] Thirdly, the present invention provides the application of the carbon fiber sizing agent described in the second aspect in the preparation of carbon fiber composite materials.

[0026] Fourthly, the present invention provides a method for preparing carbon fiber composite materials, comprising the following steps:

[0027] The carbon fiber is impregnated with the carbon fiber sizing agent described in the second aspect, and then subjected to acidification, water washing and drying treatment to obtain sized carbon fiber; the sized carbon fiber is then combined with a resin matrix and cured to obtain a carbon fiber composite material.

[0028] Furthermore, the carbon fiber is of various types or recycled carbon fiber;

[0029] The resin matrix is ​​epoxy resin, unsaturated polyester resin or polyamide resin; the mass ratio of the sized carbon fiber to the resin matrix is ​​1:(1-3);

[0030] The curing temperature is 120-140℃, and the time is 2-4 hours.

[0031] Fifthly, the present invention provides a carbon fiber composite material, which is prepared by the method for preparing the carbon fiber composite material described in the fourth aspect.

[0032] Compared with the prior art, the present invention has the following advantages:

[0033] (1) Achieving high-value closed-loop utilization of waste PMI foam. This invention converts waste PMI foam into resin degradation liquid through alkaline catalytic degradation, and uses it directly as an effective component of carbon fiber sizing agent. This avoids the low added value utilization of traditional physical recycling and the environmental pollution caused by incineration, and realizes high-value recycling from waste polymer materials to high-end composite material additives, significantly improving resource utilization.

[0034] (2) Significantly reduce the production cost of carbon fiber sizing agents. Using waste PMI foam degradation resin to replace part of the newly synthesized resin raw materials has a wide range of raw material sources, low cost, and simple degradation process that is easy to industrialize. It effectively reduces the dependence on imported raw materials and has obvious economic advantages.

[0035] (3) Improved interfacial bonding performance between carbon fiber and resin matrix. Waste PMI foam degradation resin contains abundant polar functional groups such as carboxyl groups, which can form strong interactions with the carbon fiber surface and matrix resin. At the same time, it works synergistically with compound resin and antistatic agent to significantly improve the wettability and chemical activity of carbon fiber surface. Carbon fiber treated with the sizing agent of this invention has good compatibility with various matrices such as epoxy resin, unsaturated polyester resin, and polyamide resin, effectively solving the interfacial delamination problem. The interfacial shear strength can be increased by more than 30%, and the interlaminar shear strength and flexural strength of composite materials are significantly improved.

[0036] (4) The process is environmentally friendly and the conditions are mild. The present invention uses a strong alkaline aqueous solution as the degradation system, which avoids the use of large amounts of organic solvents. The degradation temperature range is 100-260℃, the reaction pressure is controllable, and there are few by-products. The preparation process of the sizing agent uses water or low-toxicity solvents (acetone, ethanol) as diluents. The emulsification process does not require high temperature and high pressure. The overall process is green and environmentally friendly, which meets the goal of low carbon and environmental protection.

[0037] (5) Wide range of applications and strong compatibility. The method of this invention is applicable to all kinds of waste PMI foam (including processing scraps and scrapped products), as well as various types of carbon fibers including recycled carbon fibers; the sizing agent can be matched with a variety of thermosetting and thermoplastic resin matrices, providing a universal technical solution for the green manufacturing and circular economy development of carbon fiber composite materials.

[0038] In summary, this invention achieves high-value closed-loop utilization of waste PMI foam, significantly reduces the production cost of sizing agents, improves the interfacial bonding performance between carbon fiber and resin matrix, significantly increases interfacial shear strength, and the process is green and environmentally friendly, applicable to various types of carbon fiber and thermosetting / thermoplastic resin systems. Attached Figure Description

[0039] Figure 1 This is a process flow diagram of the present invention.

[0040] Figure 2 Scanning electron microscope image of sized carbon fiber.

[0041] Figure 3 In the image, (a) is a photograph of the prepared carbon fiber composite material; (b) is a photograph of the bending fracture.

[0042] Figure 4 These represent the interfacial bond strength and interlaminar shear strength of carbon fiber composites. Detailed Implementation

[0043] To further illustrate the technical solution of the present invention, the present invention will be further described below through embodiments.

[0044] Example 1

[0045] like Figure 1 As shown, a method for preparing a carbon fiber composite material in this embodiment includes the following steps:

[0046] (1) Pretreatment and degradation of waste PMI foam

[0047] Waste PMI foam (scrap and waste) generated in an aerospace processing workshop was collected. Surface oil, dust, and other impurities were removed, and the foam was washed three times with deionized water. It was then placed in a forced-air drying oven and dried at 90℃ for 3 hours until the moisture content of the foam particles decreased to 0.3%. The dried PMI foam was then mechanically pulverized into particles with an area of ​​20-30 cm². 2 Fragments.

[0048] 100g of the above-mentioned PMI foam fragments were weighed and added to a catalytic degradation system containing 10wt% sodium hydroxide aqueous solution (500mL of sodium hydroxide aqueous solution), and placed in a sealed stainless steel reactor. The reactor was heated to 180℃ and kept at that temperature for 12h, with intermittent stirring during the reaction. After the reaction was completed, the mixture was allowed to cool naturally to room temperature to obtain a homogeneous resin degradation solution, which was then used to obtain PMI foam degradation resin. The PMI foam degradation rate was determined to be 98.7% by gravimetric method.

[0049] (2) Preparation of sizing agent

[0050] Take 100 parts (by weight, the same below) of PMI foam degradation resin obtained in step (1), add 10 parts of epoxy resin (E-51 type), 0.5 parts of polyether ester amide antistatic agent, and 300 parts of diluent (ammonia and ethanol are mixed at a mass ratio of 1:1). After stirring and mixing evenly, add 1.0 part of Tween-80 emulsifier. Emulsify the emulsion at 1500 r / min for 20 min using a high-speed emulsifier until a uniform and transparent emulsion solution is formed. Filter the emulsion through a 200-mesh filter to remove insoluble matter to obtain carbon fiber sizing agent. The solid content of the sizing agent is determined to be 32.5%.

[0051] (3) Carbon fiber sizing and composite material preparation

[0052] T300 grade carbon fiber (12k) was passed through a sizing tank containing the sizing agent obtained in step (2) at a speed of 1 m / min for 30 s. After removal, it was acidified (soaked in 1 wt% acetic acid solution for 10 s), washed three times with deionized water, and then dried in an oven at 100℃ for 2 h to obtain sized carbon fiber. The sizing rate of the carbon fiber was determined to be 1.8% by weighing.

[0053] The above-mentioned sized carbon fiber and epoxy resin matrix (E-51 / curing agent system) were mixed at a mass ratio of 1:2, and the mixture was cured at 130°C for 3 hours using a compression molding process to obtain the finished carbon fiber composite material.

[0054] Example 2

[0055] The preparation method of a carbon fiber composite material in this embodiment includes the following steps:

[0056] (1) Pretreatment and degradation of waste PMI foam

[0057] Waste PMI foam from a wind turbine blade manufacturing plant was collected. After removing impurities, it was cleaned with deionized water and placed in a forced-air drying oven at 80°C for 4 hours to reduce the moisture content of the foam particles to below 0.5%. The dried PMI foam was then mechanically pulverized into 10-40 cm particles. 2 Fragments.

[0058] Weigh 100g of PMI foam fragments and add them to a catalytic degradation system containing 20wt% potassium hydroxide aqueous solution (400mL of potassium hydroxide aqueous solution). Place the mixture in a sealed high-pressure reactor. Heat to 160℃ and maintain the temperature for 8 hours. After the reaction is complete, cool to room temperature to obtain a resin degradation solution, which in turn yields PMI foam degradation resin. The PMI foam degradation rate is 97.2%.

[0059] (2) Preparation of sizing agent

[0060] Take 100 parts of PMI foam-degradable resin, add 8 parts of unsaturated polyester resin (type 196), 0.3 parts of polyethylene glycol methacrylate copolymer antistatic agent, and 250 parts of diluent (acetone and deionized water are mixed at a mass ratio of 1:1.5). After stirring and mixing evenly, add 0.8 parts of SDBS emulsifier. Emulsify using a high-speed emulsifier at 1200 r / min for 25 min to form a uniform and transparent emulsion solution. Filter through a 200-mesh filter to obtain the carbon fiber sizing agent. The solid content was determined to be 28.7%.

[0061] (3) Carbon fiber sizing and composite material preparation

[0062] The recycled carbon fibers (short-cut carbon fibers recovered through pyrolysis) were immersed in the sizing agent obtained in step (2) for 60 seconds. After being removed, they were acidified (immersed in 0.5wt% hydrochloric acid solution for 15 seconds), washed three times with deionized water, and then dried at 110℃ for 1.5 hours to obtain sized carbon fibers with a sizing rate of 2.1%. The morphology of the sized carbon fibers is shown in the attached figure. Figure 2 As shown.

[0063] The sized carbon fiber and unsaturated polyester resin were mixed at a mass ratio of 1:1.5, molded, and cured at 120°C for 4 hours to obtain the finished carbon fiber composite material.

[0064] Example 3

[0065] The preparation method of a carbon fiber composite material in this embodiment includes the following steps:

[0066] (1) Pretreatment and degradation of waste PMI foam

[0067] Waste PMI foam scraps from a rail transit vehicle manufacturing company were collected. After removing surface impurities and cleaning, the scraps were placed in a forced-air drying oven and dried at 100℃ for 2 hours to reduce the moisture content to 0.2%. The dried PMI foam was then mechanically pulverized into 1-10 cm pieces. 2 Tiny fragments.

[0068] 100g of PMI foam fragments were weighed and added to a catalytic degradation system containing 5wt% lithium hydroxide aqueous solution (600mL of lithium hydroxide aqueous solution), and placed in a sealed reactor. The temperature was raised to 220℃ and the reaction was maintained for 6 hours. After the reaction was completed, the mixture was cooled to room temperature to obtain a resin degradation solution, which in turn yielded PMI foam degradation resin. The PMI foam degradation rate was 99.1%.

[0069] (2) Preparation of sizing agent

[0070] Take 100 parts of PMI foam-degradable resin, add 12 parts of polyamide resin (PA6 type), 0.8 parts of polyether ester amide antistatic agent, and 350 parts of diluent (ethanol and deionized water are mixed at a mass ratio of 1:2). After stirring and mixing evenly, add 1.5 parts of emulsifier, which is a compound of Tween-80 and SDBS at a mass ratio of 1:1.2. Emulsify the mixture for 15 minutes at 1800 r / min using a high-speed emulsifier to form a uniform and transparent emulsion solution. Filter through a 200-mesh filter to obtain the carbon fiber sizing agent. The solid content was determined to be 36.2%.

[0071] (3) Carbon fiber sizing and composite material preparation

[0072] T700 grade carbon fiber (24k) was immersed in the sizing agent obtained in step (2) at a rate of 0.8 m / min for 40s. After being taken out, it was acidified (immersed in 1wt% acetic acid solution for 10s), washed with water, and dried at 110℃ for 2h to obtain sized carbon fiber with a sizing rate of 2.3%.

[0073] The sized carbon fiber and polyamide resin (PA6) were mixed at a mass ratio of 1:2.5, injection molded, and cured at 140℃ for 2 hours to obtain the finished carbon fiber composite material.

[0074] Example 4

[0075] The preparation method of a carbon fiber composite material in this embodiment includes the following steps:

[0076] (1) Pretreatment and degradation of waste PMI foam

[0077] Collect waste PMI foam products (waste packaging materials and processing waste), remove impurities and clean them, place them in a forced-air drying oven and dry them at 85℃ for 3.5 hours until the moisture content is ≤0.4%. Mechanically crush the dried PMI foam into fragments of 30-50cm².

[0078] Weigh 100g of PMI foam fragments and add them to a catalytic degradation system containing 25wt% sodium hydroxide aqueous solution (350mL of sodium hydroxide aqueous solution), and place the mixture in a sealed reactor. Heat to 140℃ and maintain the temperature for 20h. After the reaction is complete, cool to room temperature to obtain the resin degradation solution, with a PMI foam degradation rate of 96.5%.

[0079] (2) Preparation of sizing agent

[0080] Take 100 parts of PMI foam-degradable resin, add 6 parts of polyvinyl alcohol resin (PVA-1788 type), 0.2 parts of polyethylene glycol methacrylate copolymer antistatic agent, and 200 parts of diluent (acetone and ethanol mixed at a mass ratio of 1:1.8). After stirring and mixing evenly, add 0.6 parts of Tween-80 emulsifier. Emulsify using a high-speed emulsifier at 1000 r / min for 30 min to form a uniform and transparent emulsion solution. Filter through a 200-mesh filter to obtain the carbon fiber sizing agent. The solid content was determined to be 40.5%.

[0081] (3) Carbon fiber sizing and composite material preparation

[0082] M40 grade carbon fiber was immersed in the sizing agent obtained in step (2) at a rate of 1.2 m / min for 25s. After being taken out, it was acidified (immersed in 1wt% acetic acid solution for 8s), washed with water, and dried at 105℃ for 2h to obtain sized carbon fiber with a sizing rate of 1.5%.

[0083] The sized carbon fiber and epoxy resin matrix are mixed at a mass ratio of 1:3, molded, and cured at 130℃ for 3 hours to obtain the finished carbon fiber composite material.

[0084] Example 5

[0085] The preparation method of a carbon fiber composite material in this embodiment includes the following steps:

[0086] (1) Pretreatment and degradation of waste PMI foam

[0087] Waste PMI foam was collected, impurities were removed and the foam was washed. It was then placed in a forced-air drying oven and dried at 95°C for 2.5 hours until the moisture content was reduced to below 0.3%. The dried PMI foam was then mechanically pulverized into 40-60 cm pieces. 2 Fragments.

[0088] Weigh 100g of PMI foam fragments and add them to a catalytic degradation system containing 30wt% potassium hydroxide aqueous solution (300mL of potassium hydroxide aqueous solution), and place the mixture in a sealed reactor. Heat to 250℃ and maintain the temperature for 3 hours. After the reaction is complete, cool to room temperature to obtain the resin degradation solution. The PMI foam degradation rate is 99.5%.

[0089] (2) Preparation of sizing agent

[0090] Take 100 parts of PMI foam-degradable resin, add 14 parts of epoxy resin (E-44 type), 0.9 parts of polyether ester amide antistatic agent, and 380 parts of diluent (acetone, ethanol, and deionized water mixed in a mass ratio of 1:1:1). After stirring and mixing evenly, add 1.8 parts of SDBS emulsifier. Emulsify using a high-speed emulsifier at 2000 r / min for 18 min to form a uniform and transparent emulsion solution. Filter through a 200-mesh filter to obtain the carbon fiber sizing agent. The solid content was determined to be 25.3%.

[0091] (3) Carbon fiber sizing and composite material preparation

[0092] T800 grade carbon fiber was immersed in the sizing agent obtained in step (2) at a rate of 0.5 m / min for 50s. After being taken out, it was acidified (immersed in 1wt% acetic acid solution for 12s), washed with water, and dried at 100℃ for 2.5h to obtain sized carbon fiber with a sizing rate of 2.5%.

[0093] Sizing of carbon fiber and epoxy resin matrix were mixed at a mass ratio of 1:2, molded, and cured at 135℃ for 2.5 hours to obtain the finished carbon fiber composite material. Using the short beam shear method, with sample dimensions of 20mm long × 6mm wide × 2mm thick (span-to-thickness ratio 4:1) and a loading rate of 1mm / min, the interlaminar shear strength of the composite material was measured to be 97.5 MPa. Figure 4 As shown.

[0094] Example 6

[0095] The preparation method of a carbon fiber composite material in this embodiment includes the following steps:

[0096] (1) Pretreatment and degradation of waste PMI foam

[0097] Collect waste PMI foam (waste building insulation materials and processing scraps), remove surface impurities, wash with deionized water, and then place it in a forced-air drying oven at 90℃ for 3 hours to achieve a moisture content ≤0.3%. Mechanically pulverize the dried PMI foam into 15-25 cm pieces. 2 Fragments.

[0098] Weigh 100g of PMI foam fragments and add them to a catalytic degradation system containing 15wt% sodium hydroxide aqueous solution (450mL of sodium hydroxide aqueous solution), and place the mixture in a sealed reactor. Heat to 200℃ and maintain the temperature for 10h. After the reaction is complete, cool to room temperature to obtain the resin degradation solution. The PMI foam degradation rate is 98.2%.

[0099] (2) Preparation of sizing agent

[0100] Take 100 parts of PMI foam-degradable resin, add 5 parts of unsaturated polyester resin (type 191), 0.1 parts of polyethylene glycol methacrylate copolymer antistatic agent, and 400 parts of diluent (ethanol and deionized water mixed at a mass ratio of 1:1.2). After stirring and mixing evenly, add 2.0 parts of emulsifier, a compound of Tween-80 and SDBS at a mass ratio of 1:1.5. Emulsify using a high-speed emulsifier at 1600 r / min for 22 min to form a uniform and transparent emulsion solution. Filter through a 200-mesh filter to obtain the carbon fiber sizing agent. The solid content was determined to be 21.8%.

[0101] (3) Carbon fiber sizing and composite material preparation

[0102] The recycled carbon fiber (short-cut carbon fiber that has been mechanically recycled) was immersed in the sizing agent obtained in step (2) for 45 seconds. After being taken out, it was acidified (immersed in 0.5wt% hydrochloric acid solution for 12 seconds), washed with deionized water 3 times, and then dried at 105℃ for 2 hours to obtain sized carbon fiber with a sizing rate of 1.9%.

[0103] Sizingd carbon fiber and unsaturated polyester resin were mixed at a mass ratio of 1:1.8, molded, and cured at 125℃ for 3.5 hours to obtain the finished carbon fiber composite material. The strength of the composite material under bending load was tested using a three-point bending loading method, and its bending strength was found to be 1164 MPa. Images of the material before and after fracture are shown below. Figure 3 As shown, the flexural strength before and after modification is as follows: Figure 4 As shown.

[0104] Example 7

[0105] The preparation method of a carbon fiber composite material in this embodiment includes the following steps:

[0106] (1) Pretreatment and degradation of waste PMI foam

[0107] Collect waste PMI foam (fragments and substandard products from wind power, automotive, and other fields), remove surface impurities, wash with deionized water, and place in a forced-air drying oven to dry at 95℃ for 2 hours until the moisture content is ≤0.3%. Mechanically pulverize the dried PMI foam into 10-30 cm pieces. 2 Fragments.

[0108] Weigh 100g of PMI foam fragments and add them to a catalytic degradation system containing 20wt% sodium hydroxide aqueous solution (450mL of sodium hydroxide aqueous solution), and place the mixture in a sealed reactor. Heat to 180℃ and maintain the temperature for 12h. After the reaction is complete, cool to room temperature to obtain the resin degradation solution, with a PMI foam degradation rate of 98.7%.

[0109] (2) Preparation of sizing agent

[0110] Take 100 parts of PMI foam-degradable resin, add 6 parts of unsaturated polyester resin (type 191), 0.1 parts of polyethylene glycol methacrylate copolymer antistatic agent, and 500 parts of diluent (ethanol and deionized water mixed at a mass ratio of 1:1.5). After stirring and mixing evenly, add 2.0 parts of emulsifier compounded from Tween-80 and SDBS at a mass ratio of 1:1.3. Emulsify using a high-speed emulsifier at 1800 r / min for 20 min to form a uniform and transparent emulsion solution. Filter through a 200-mesh filter to obtain the carbon fiber sizing agent. The solid content was determined to be 22.3%.

[0111] (3) Carbon fiber sizing and composite material preparation

[0112] HTS40 carbon fiber was immersed in the sizing agent obtained in step (2) for 80 seconds. After being taken out, it was acidified (immersed in 20wt% phosphoric acid solution for 15 seconds), washed three times with deionized water, and then dried at 100℃ for 2 hours to obtain sized carbon fiber with a sizing rate of 2%.

[0113] Sizingd carbon fiber and cyclic AG-80 epoxy resin were mixed at a mass ratio of 1:2.1, molded, and cured at 60℃ for 4 hours to obtain the finished carbon fiber composite material. The strength of the composite material under bending load was tested using a three-point bending loading method, and its bending strength was found to be 998 MPa.

[0114] Example 8

[0115] The preparation method of a carbon fiber composite material in this embodiment includes the following steps:

[0116] (1) Pretreatment and degradation of waste PMI foam

[0117] Waste PMI (Polymer Oxide) scraps from an aerospace manufacturing workshop were collected. Surface oil, dust, and other impurities were removed, and the foam was washed three times with deionized water. It was then placed in a forced-air drying oven and dried at 80°C for 6 hours until the moisture content of the foam particles decreased to 0.2%. The dried PMI foam was then mechanically pulverized into particles with an area of ​​25-35 cm². 2 Fragments.

[0118] 100g of the above-mentioned PMI foam fragments were weighed and added to a catalytic degradation system containing 15wt% potassium hydroxide aqueous solution (500mL of sodium hydroxide aqueous solution was used), and placed in a sealed stainless steel reactor. The reactor was heated to 190℃ and kept at that temperature for 10h, with intermittent stirring during the reaction. After the reaction was completed, the mixture was allowed to cool naturally to room temperature to obtain a homogeneous resin degradation solution, which was then used to obtain PMI foam degradation resin. The PMI foam degradation rate was determined to be 97.9% by gravimetric method.

[0119] (2) Preparation of sizing agent

[0120] Take 100 parts of the PMI foam degradation resin obtained in step (1), add 15 parts of epoxy resin (E-51 type), 0.2 parts of polyether ester amide antistatic agent, and 300 parts of diluent (acetone and ethanol mixed at a mass ratio of 1:1.2). After stirring and mixing evenly, add 1.0 part of emulsifier, which is a compound of Tween-80 and SDBS at a mass ratio of 1:1.2. Emulsify the emulsion at 1500 r / min for 30 min using a high-speed emulsifier until a uniform and transparent emulsion solution is formed. Filter the emulsion through a 200-mesh filter to remove insoluble matter to obtain the carbon fiber sizing agent. The solid content of the sizing agent is determined to be 31.8%.

[0121] (3) Carbon fiber sizing and composite material preparation

[0122] AS7 grade carbon fiber was passed through a sizing tank containing the sizing agent obtained in step (2) at a speed of 1.2 m / min for 40 s. After removal, it was acidified (soaked in 20 wt% phosphoric acid solution for 15 s), washed three times with deionized water, and then dried in an oven at 100 ℃ for 2 h to obtain sized carbon fiber. The sizing rate of the carbon fiber was determined to be 2.0% by weighing.

[0123] The above-mentioned sized carbon fiber and epoxy resin matrix (E-51 / curing agent system) were mixed at a volume ratio of 1:1, and the mixture was cured at 160°C for 2 hours using a compression molding process to obtain the finished carbon fiber composite material.

[0124] Example 9

[0125] The preparation method of a carbon fiber composite material in this embodiment includes the following steps:

[0126] (1) Pretreatment and degradation of waste PMI foam

[0127] Waste PMI foam scraps were collected from a battery protection plate manufacturer of new energy vehicles. After removing surface impurities and cleaning, the scraps were placed in a forced-air drying oven and dried at 90℃ for 3 hours to reduce the moisture content to 0.3%. The dried PMI foam was then mechanically pulverized into 10-20 cm pieces. 2 Small fragments.

[0128] Weigh 110g of PMI foam fragments and add them to a catalytic degradation system containing 5wt% lithium hydroxide aqueous solution (500mL of lithium hydroxide aqueous solution), and place the mixture in a sealed reactor. Heat to 200℃ and maintain the temperature for 10h. After the reaction is complete, cool to room temperature to obtain a resin degradation solution, which in turn yields PMI foam degradation resin. The PMI foam degradation rate is 98.4%.

[0129] (2) Preparation of sizing agent

[0130] Take 100 parts of PMI foam-degradable resin, add 10 parts of polyamide resin (PA6 type), 0.6 parts of polyether ester amide antistatic agent, and 300 parts of diluent (ethanol and deionized water are mixed at a mass ratio of 1:2). After stirring and mixing evenly, add 1.5 parts of emulsifier, a mixture of Tween-80 and SDBS at a mass ratio of 1:1. Emulsify using a high-speed emulsifier at 1500 r / min for 20 min to form a uniform and transparent emulsion solution. Filter through a 200-mesh filter to obtain the carbon fiber sizing agent. The solid content was determined to be 35.8%.

[0131] (3) Carbon fiber sizing and composite material preparation

[0132] T700 grade carbon fiber (24k) was impregnated with the sizing agent obtained in step (2) at a rate of 1.0 m / min for 60s. After being taken out, it was acidified (immersed in 1wt% acetic acid solution for 10s), washed with water, and dried at 100℃ for 2h to obtain sized carbon fiber with a sizing rate of 2.1%.

[0133] The sized carbon fiber and polyamide resin (PA6) were mixed at a mass ratio of 1:2.4, injection molded, and cured at 150°C for 1.5 hours to obtain the finished carbon fiber composite material.

[0134] Example 10

[0135] The preparation method of a carbon fiber composite material in this embodiment includes the following steps:

[0136] (1) Pretreatment and degradation of waste PMI foam

[0137] Waste PMI foam was collected, impurities were removed and the foam was washed. It was then placed in a forced-air drying oven and dried at 100°C for 1.5 hours until the moisture content was reduced to below 0.4%. The dried PMI foam was then mechanically pulverized into 30-60 cm pieces. 2 Fragments.

[0138] Weigh 100g of PMI foam fragments and add them to a catalytic degradation system containing 20wt% sodium hydroxide aqueous solution (400mL of sodium hydroxide aqueous solution), and place the mixture in a sealed reactor. Heat to 220℃ and maintain the temperature for 5 hours. After the reaction is complete, cool to room temperature to obtain the resin degradation solution. The PMI foam degradation rate is 99.1%.

[0139] (2) Preparation of sizing agent

[0140] Take 100 parts of PMI foam-degradable resin, add 15 parts of epoxy resin (E-44 type), 1.1 parts of polyether ester amide antistatic agent, and 360 parts of diluent (acetone, ethanol, and deionized water mixed in a mass ratio of 1:1:1). After stirring and mixing evenly, add 1.6 parts of SDBS emulsifier. Emulsify using a high-speed emulsifier at 2000 r / min for 25 min to form a uniform and transparent emulsion solution. Filter through a 200-mesh filter to obtain the carbon fiber sizing agent. The solid content was determined to be 29.8%.

[0141] (3) Carbon fiber sizing and composite material preparation

[0142] H3055 grade carbon fiber was immersed in the sizing agent obtained in step (2) at a rate of 0.5 m / min for 40s. After being taken out, it was acidified (immersed in 0.5wt% hydrochloric acid solution for 15s), washed with water, and dried at 100℃ for 2h to obtain sized carbon fiber with a sizing rate of 2.8%.

[0143] The sized carbon fiber and epoxy resin matrix were mixed at a mass ratio of 1:3, molded, and cured at 165℃ for 2 hours to obtain the finished carbon fiber composite material. Using the short beam shear method, with a sample size of 20mm long × 6mm wide × 2mm thick (span-to-thickness ratio of 4:1) and a loading rate of 1mm / min, the interlaminar shear strength of the composite material was measured to be 94.9 MPa.

[0144] The foregoing has shown and described the main features and advantages of the present invention. It will be apparent to those skilled in the art that the present 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 its spirit or essential characteristics. 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. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0145] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing carbon fiber sizing agent using waste PMI foam, characterized in that, Includes the following steps: (1) Collect waste PMI foam and pretreat it to obtain PMI foam fragments; add the PMI foam fragments to the catalytic degradation system to carry out the degradation reaction until PMI is completely degraded, cool to room temperature to obtain resin degradation liquid, and then obtain PMI foam degradation resin. (2) The PMI foam degradation resin obtained in step (1) is mixed with compound resin, antistatic agent and diluent in a certain mass ratio, and then an emulsifier is added for emulsification treatment until a uniform and transparent emulsion solution is formed. The insoluble matter is removed by filtration to obtain carbon fiber sizing agent.

2. The method for preparing carbon fiber sizing agent using waste PMI foam according to claim 1, characterized in that, The pretreatment in step (1) includes removing impurities and washing, drying, crushing into fragments, drying at a temperature of 80-100℃ for 2-4 hours, and the fragment size being 1-60cm. 2 ; The catalytic degradation system is a strong alkaline aqueous solution, where the strong alkaline is sodium hydroxide, potassium hydroxide, or lithium hydroxide, with a concentration of 1-30 wt%. The ratio of PMI foam fragments to the strong alkaline aqueous solution is 100 g: 300-600 mL. The degradation reaction temperature is 100-260℃, and the degradation reaction time is 2-24h.

3. The method for preparing carbon fiber sizing agent using waste PMI foam according to claim 1, characterized in that, In step (2), the mass ratio of PMI foam degradation resin, compound resin, antistatic agent, diluent and emulsifier is 100:(5-15):(0.1-1.0):(200-400):(0.5-2.0). The compounded resin is a thermoplastic resin or a thermosetting resin; The antistatic agent is polyvinyl alcohol, ethylene glycol methacrylate copolymer or polyether ester amide; The diluent is one or a mixture of two of acetone, ethanol, and deionized water; The emulsifier is one or a mixture of two of the following: polyoxyethylene, sorbitan fatty acid ester, and sodium dodecylbenzene sulfonate.

4. The method for preparing carbon fiber sizing agent using waste PMI foam according to claim 3, characterized in that, The thermoplastic resin is selected from polyamide resin and polyvinyl alcohol resin, and the thermosetting resin is selected from epoxy resin and unsaturated polyester resin.

5. The method for preparing carbon fiber sizing agent using waste PMI foam according to claim 1, characterized in that, In step (2), the rotation speed of the emulsification process is 1000-2000 r / min and the time is 15-30 min; the solid content of the sizing agent obtained after emulsification is controlled at 10%-60%.

6. The carbon fiber sizing agent prepared by the method of preparing carbon fiber sizing agent using waste PMI foam as described in any one of claims 1-5.

7. The application of the carbon fiber sizing agent according to claim 6 in the preparation of carbon fiber composite materials.

8. A method for preparing carbon fiber composite material, characterized in that, Includes the following steps: Carbon fibers are impregnated with the carbon fiber sizing agent described in claim 6, and then subjected to acidification, water washing, and drying treatment to obtain sized carbon fibers; The sized carbon fiber is combined with a resin matrix and cured to obtain a carbon fiber composite material.

9. The method for preparing a carbon fiber composite material according to claim 8, characterized in that, The carbon fiber is of various types or recycled carbon fiber; The resin matrix is ​​epoxy resin, unsaturated polyester resin or polyamide resin; the mass ratio of the sized carbon fiber to the resin matrix is ​​1:(1-3); The curing temperature is 60-160℃, and the time is 2-4 hours.

10. The carbon fiber composite material prepared by the method of claim 8.

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