Preparation method of resveratrol-based epoxy Vitrimers / carbon fiber composite material and carbon fiber recovery process

Abstract

The invention provides a preparation method of a recoverable resveratrol-based epoxy Vitrimers / carbon fiber composite material and a carbon fiber recovery process, and is characterized in that resveratrol-based epoxy resin is used as a substrate, and all or part of epoxy groups on the resveratrol-based epoxy resin are esterified; wherein the esterified groups comprise ester groups which partially contain disulfide bonds. According to the carbon fiber composite material prepared based on the method, efficient recovery of the resin and the carbon fibers can be achieved through a mild solvent method. The problems that an existing epoxy resin-based carbon fiber composite material is unrecyclable, depends on petroleum raw materials and the like are effectively solved.

Description

Technical Field

[0001] The present invention relates to the field of polymer technology, and in particular to a preparation method of a recyclable bio-based epoxy Vitrimers resin and application thereof in carbon fiber composite materials. Background Art

[0002] In the past, carbon fiber composite waste was primarily disposed of through incineration and landfilling. However, these processes not only damage the natural environment but also result in significant waste of resources. Consequently, many countries have banned these methods of carbon fiber composite waste disposal. Research and development of low-energy, green, economical, and environmentally friendly carbon fiber composite recycling technologies has become a hot topic. This is of great significance for responding to the call for low-carbon emissions and achieving the goal of "carbon neutrality."

[0003] However, carbon fiber reinforced plastic (CFRP) waste is currently difficult to recycle. Traditional thermoset resins, due to their stable cross-linked structures, make it difficult to separate and reuse the carbon fibers, resulting in resource waste and environmental pollution. Vitrimers are a third class of polymers, in addition to the two traditional polymers. Vitrimers possess a cross-linked network structure similar to thermosets, but their internal dynamic covalent bonds make them less permanent than thermoset networks. External stimuli can induce exchange reactions within the dynamic covalent bonds between polymer chains, causing the topology of the vitrimers to rearrange without sacrificing covalent bonds or cross-link density. This property allows vitrimers to be reprocessed like thermoplastics when exposed to external stimuli without losing network integrity. Once the external stimuli subside, vitrimers regain the strength, dimensional stability, and chemical resistance of thermosets. Vitrimers also exhibit reprocessability, self-repairing, and self-healing properties. Because epoxy resins contain a large number of epoxy groups and polycarboxylic acids or anhydrides serve as their primary curing agents, vitrimers are readily applicable in epoxy / carboxylic acid and epoxy / anhydride systems. The dynamic covalent bonds involved in the epoxy vitrimers reported so far include disulfide bond exchange, imine bond exchange, ester bond exchange, etc.

[0004] Although the chemical recycling method based on dynamic covalent bonds provides a new approach to this problem, existing epoxy Vitrimers still face problems such as non-renewable raw materials, difficulty in balancing dynamic properties and mechanical strength, and insufficient applicability for industrial production. Some units have developed anhydride-cured glassy epoxy resin materials based on ester exchange. Vitrimers still use bisphenol A as the matrix. Although ester exchange recyclability has been achieved, the problem of non-renewable raw materials has not been solved. Secondly, although bio-based Vitrimers (such as eugenol and rosin-based) have been studied, their thermomechanical properties (such as modulus and Tg) are often lower than those of petroleum-based materials. Summary of the Invention

[0005] The present invention uses the natural polyphenol compound resveratrol as a raw material, and utilizes its multifunctional properties to construct a branched bio-based epoxy resin. It uses lipoic acid containing dynamic disulfide bonds as a crosslinker, and natural polycarboxylic acid / anhydride curing agents. By regulating the ratio of the two, the dynamic exchange performance and mechanical strength of epoxy vitrimers are synergistically optimized. Specifically, its active hydroxyl groups can provide a branched structure for the epoxy resin, while the dynamic disulfide bonds of lipoic acid can impart vitrimers characteristics to the material, namely dynamic exchange properties such as self-repairing and remodeling. Natural polycarboxylic acids / anhydrides can achieve regulation of the material's mechanical properties. Therefore, the carbon fiber composite material prepared based on this can achieve 100% recovery of the resin and carbon fiber through a mild solvent method. This effectively solves the problems of existing epoxy resin-based carbon fiber composite materials, such as non-recyclability and dependence on petroleum raw materials.

[0006] The present invention provides a recyclable resveratrol-based epoxy Vitrimers, which is characterized by: using a resveratrol-based epoxy resin as a substrate, and all or part of the epoxy groups thereon are esterified;

[0007] The esterified groups mentioned above include some ester groups containing disulfide bonds.

[0008] Furthermore, the present invention provides a recyclable resveratrol-based epoxy Vitrimers, characterized by being a monomeric network compound having the structure shown below:

[0009]

[0010] n=1-5.

[0011] Furthermore, the present invention provides a method for preparing the recyclable resveratrol-based epoxy Vitrimers, characterized by:

[0012] Using the natural polyphenol compound resveratrol as raw material, a bio-based epoxy resin with a branched structure is constructed through its multifunctional properties;

[0013] Among them, an acid containing a dynamic disulfide bond is used to form a dynamic bond with an epoxy group to regulate the dynamic exchange properties of epoxy Vitrimers;

[0014] The mechanical strength of epoxy Vitrimers is regulated by curing reaction between natural polycarboxylic acids / anhydrides and epoxy groups.

[0015] Furthermore, the present invention provides a composite material for use in the manufacture of carbon fiber composite materials, characterized in that it comprises a resin system;

[0016] The resin system comprises a resveratrol-based epoxy resin, an acid containing a dynamic disulfide bond, and a polyacid or anhydride.

[0017] Furthermore, the present invention provides a composite material for manufacturing carbon fiber composite materials, characterized in that the molar ratio of resveratrol-based epoxy resin, acid containing dynamic disulfide bonds and polyacid or anhydride is 5:0.5-10:3-10.

[0018] Furthermore, the present invention provides a composite material for the manufacture of carbon fiber composite materials, characterized in that: the preparation method of the above-mentioned resveratrol-based epoxy resin is to react resveratrol with epichlorohydrin under alkaline conditions at 80-120°C for 5-8 hours to prepare a resveratrol-based epoxy resin with an epoxy value of 0.4-0.6 mol / 100g.

[0019] Furthermore, the present invention provides a method for preparing a carbon fiber composite material, characterized in that:

[0020] The resveratrol-based epoxy resin, the acid containing a dynamic disulfide bond, and the polyacid or acid anhydride are uniformly mixed to form a resin system;

[0021] After the resin system is evenly applied to the carbon fiber laminate, it is placed in a hot pressing mold and hot-pressed and cured at a temperature of 80-150°C under a pressure of 2-10 MPa. The curing time is maintained at 4-10 hours to obtain a Vitrimers epoxy resin-based carbon fiber composite material.

[0022] In addition, the present invention also provides a method for recycling the above-mentioned carbon fiber composite material, which is characterized by:

[0023] The carbon fiber composite material is immersed in a mixed solution of DMF (N,N-dimethylformamide) and mercaptoethanol and ultrasonically vibrated for 0.5-1 hour; the solution is heated to 80-120°C and soaked for 24-48 hours, then cooled to room temperature, and the carbon fiber cloth is obtained by filtration separation. After washing with DMF, the recovered carbon fiber plain fabric sample is obtained after drying in an oven.

[0024] Furthermore, the carbon fiber composite material recycling method provided by the present invention is characterized in that:

[0025] The volume ratio of the above-mentioned DMF to mercaptoethanol is 1-5:0-5.

[0026] Furthermore, the carbon fiber composite material recycling method provided by the present invention is characterized in that:

[0027] The amount of the carbon fiber composite material and the mixed solution is 10-20 mL of the mixed solution per gram of the carbon fiber composite material.

[0028] Compared with the prior art, the advantages of the present invention are:

[0029] The present invention utilizes the dynamic reversible reaction of epoxy resin containing dynamic covalent bonds under specific conditions to achieve the dissolution and recovery of epoxy resin, thereby completing the recycling of carbon fibers in carbon fiber composite materials. Specifically, the present invention uses a bio-based epoxy resin with multifunctionality to cure the epoxy resin with a disulfide bond and other natural polycarboxylic acids / anhydrides as a curing agent to prepare a bio-based epoxy Vitrimers resin, and the carbon fiber composite material prepared with this bio-based epoxy resin as the matrix is ​​recycled from the carbon fiber. This solves the problem that carbon fiber composite materials are difficult to recycle. Compared with other epoxy Vitrimers, the bio-based resin of this application is more conducive to recycling, can be applied to large-scale industrial production, and is conducive to promotion to the application of carbon fiber composite materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 , infrared spectrum of the product of Example 1;

[0031] Figure 2 , Raman spectrum of the product of Example 1;

[0032] Figure 3 , the product of Example 1 1 H NMR spectrum. DETAILED DESCRIPTION

[0033] Experimental methods

[0034] 1. Synthesis of resveratrol-based epoxy resin:

[0035] The reaction proceeds as shown below:

[0036]

[0037] n is 1-5, and generally n is 1 according to the following reaction conditions.

[0038] The reaction method involves combining resveratrol and epichlorohydrin in a molar ratio of 1:4-1:8. A ratio below or exceeding this will result in incomplete reaction and excessive byproducts. Under alkaline conditions, the mixture is stirred rapidly at 80-120°C for 5-8 hours to produce a resveratrol-based epoxy resin with an epoxy value of 0.4-0.6 mol / 100g.

[0039] 2. Preparation of Vitrimers epoxy resin-based carbon fiber composites:

[0040] The reaction proceeds as shown below:

[0041]

[0042] The reaction method is as follows: pre-synthesized resveratrol-based epoxy resin (GPC test results of epoxy resin RE synthesized by the above method show that the average molecular weight of RE is Mn = 1.18×10 3 ) and thioctic acid and anhydride curing agent are uniformly mixed in a molar ratio of 5: (0.5-10): (3-10) (preferably 5: 0.5-3: 3-6). The resin system is evenly applied to carbon fiber (T300 grade, 3K, 240g / m 2 ) After lamination, it is placed in a hot pressing mold and hot pressing curing treatment is carried out under a pressure of 5-10 MPa and the temperature is controlled in the range of 80-150°C. The curing time is maintained at 4-10 hours, preferably 5-8 hours, to prepare Vitrimers epoxy resin-based carbon fiber composite materials.

[0043] 3. Recycling of carbon fiber composite materials

[0044] The composite material prepared above was immersed in a mixed solution of DMF and mercaptoethanol (DMF and mercaptoethanol are the best mixed solvents, and other solvents cannot achieve effective recovery) (volume ratio of 1-5:0-5, and the volume ratios of 1:1, 1:2, and 1:3 were the best ratios after testing. The recovery efficiency of other ratios within the range of 1-5:0:5 was slightly lower, but beyond this ratio, a recovery effect of more than 80% could not be achieved). The material was ultrasonically vibrated at 100Hz for 30 minutes; then the material was transferred to a solvent environment at 80-120℃ and continued to be immersed for 24-48 hours to fully dissolve the resin. The carbon fiber with a clean surface was obtained by filtration separation, and the recovery rate could be as high as 100%.

[0045] Example 1 (optimal solution)

[0046] Step (1) 0.1 mol of resveratrol and 0.6 mol of epichlorohydrin (ECH) were added to a reaction vessel and stirred at 100° C. and 500 rpm for 2 hours. 50 mL of a 20% w / w sodium hydroxide aqueous solution was slowly added dropwise to the reaction mixture, and the mixture was stirred for another 5 hours. The mixture was then cooled to room temperature. The suspension was diluted with dichloromethane, and the upper aqueous phase was removed. The organic phase was washed three times with distilled water and dried over anhydrous magnesium sulfate to obtain a resveratrol-based epoxy resin having an epoxide value of 0.4-0.6 mol / 100 g and an average degree of polymerization (n) of 1-5.

[0047] Step (2) A resveratrol-based epoxy resin (RE) is uniformly mixed with lipoic acid (LA) and an anhydride curing agent (e.g., phthalic anhydride) in a molar ratio of 5:1:4 to form a resin system. Ten layers of 3K carbon fiber plain weave fabric are stacked in a mold, and the resin system is evenly coated on the fiber surface. The fiber surface is then hot-pressed and cured at a pressure of 5 MPa and a temperature of 100°C for 6 hours to produce a composite material with a fiber content of 60%. (Tests have shown that a higher coating amount has minimal effect on the recovery rate; it only achieves a difference in the performance of the composite material itself.)

[0048] Step (3) 4 g of the composite material prepared above was immersed in 50 mL of a mixed solution of DMF and mercaptoethanol (volume ratio 1:1) and ultrasonically vibrated at 100 Hz for 30 min; the solution was heated to 100° C. and continued to be immersed for 48 hours, then cooled to room temperature, and the carbon fiber cloth was obtained by filtration and separation. The carbon fiber cloth was washed three times with DMF and dried in an oven at 100° C. to obtain a recovered carbon fiber cloth with a recovery rate of 100%.

[0049] 4. Structural Characterization

[0050] In this example, the curing reaction of resveratrol-based epoxy Vitrimers resin was characterized and analyzed by infrared spectroscopy and Raman spectroscopy. Figure 1 As shown, the infrared spectra of the raw materials resveratrol epoxy resin (RE) and lipoic acid (LA) are compared. The product has a 911 cm -1 The characteristic peak of epoxy group at 1682cm -1 The characteristic peak of carboxyl group at 1720 cm -1 An obvious ester bond (C=O) stretching vibration peak appeared at the position, and the peak intensity was significantly enhanced. The appearance of this characteristic peak further confirmed that the epoxy group and the carboxyl group successfully underwent a ring-opening esterification reaction.

[0051] Raman spectroscopy analysis results ( Figure 2 ) provides important evidence for the resin curing reaction. Comparing the Raman spectra of lipoic acid (LA) and the cured product, it can be found that both have a peak at 500 cm -1The characteristic peak of SS bond is shown nearby, which is consistent with the infrared spectrum analysis and proves that the epoxy group reacts with the carboxyl group.

[0052] The H-NMR spectrum of the product after curing reaction ( Figure 3 ) showed that the peaks at 6.0-7.0 ppm and 7.3 ppm were attributed to the characteristic proton signals of the C=C double bond and benzene ring in the resveratrol structure. The peak in the 1.50-1.86 ppm range was attributed to the characteristic proton signal of the methylene group (-CH2-) in the non-cyclic structure of lipoic acid. Simultaneously, the characteristic proton peak of the resveratrol epoxy group (2.7 ppm) disappeared, indicating that the epoxy group had undergone a ring-opening reaction and curing was complete.

[0053] Comparative Example 1 (without adding polyacid or anhydride curing agent)

[0054] Steps (1, 3) are the same as those in Example 1.

[0055] Step (2) uniformly mixes resveratrol-based epoxy resin (RE) and lipoic acid (LA) in a molar ratio of 5:1 to form a resin system. Ten layers of 3K carbon fiber plain weave fabric are stacked in a mold, and the resin system is uniformly coated on the fiber surface. The composite material is hot-pressed and cured at a pressure of 5 MPa and a temperature of 100°C for 6 hours to obtain a composite material with a fiber content of 60%.

[0056] The resin of the composite material is in an obviously soft state after being cured.

[0057] Comparative Example 2 (without adding thioctic acid)

[0058] Step (1) is the same as step (1) of Example 1

[0059] Step (2) uniformly mixes resveratrol-based epoxy resin (RE) and phthalic anhydride in a molar ratio of 5:4 to form a resin system. Ten layers of 3K carbon fiber plain weave fabric are stacked in a mold, and the resin system is uniformly coated on the fiber surface. The composite material is hot-pressed and cured at a pressure of 5 MPa and a temperature of 100°C for 6 hours to obtain a composite material with a fiber content of 60%.

[0060] The composite material has higher strength than the product of Comparative Example 2, but the matrix resin is insoluble in the solvent and the carbon fiber cloth cannot be recycled.

[0061] Table 1 The following is a comparison of the tensile strength and recovery rate of each product in the above test example

[0062] sample Tensile strength (MPa) Carbon fiber recovery rate (%) Example 1 464 100 Comparative Example 1 Too soft to measure 100 Comparative Example 2 482 Cannot be recycled

[0063] Example 2 (Changing Phthalic Anhydride to Citric Acid)

[0064] Steps (1, 3) are the same as those in Example 1.

[0065] Step (2) uniformly mixes a resveratrol-based epoxy resin (RE) with lipoic acid (LA) and citric acid in a molar ratio of 5:1:4 to form a resin system. Ten layers of 3K carbon fiber plain weave fabric are stacked in a mold, and the resin system is uniformly coated on the fiber surface. The composite material is hot-pressed and cured at a pressure of 5 MPa and a temperature of 100°C for 6 hours to obtain a composite material with a fiber content of 60%.

[0066] The resin of the composite material is in an obviously soft state after being cured.

[0067] Example 3 (changing lipoic acid to dihydrolipoic acid)

[0068] Step (1) is the same as step (1) of Example 1

[0069] Step (2) uniformly mixes resveratrol-based epoxy resin (RE), dihydrolipoic acid, and phthalic anhydride in a molar ratio of 5:1:4 to form a resin system. Ten layers of 3K carbon fiber plain weave fabric are stacked in a mold, and the resin system is uniformly coated on the fiber surface. The composite material is hot-pressed and cured at a pressure of 5 MPa and a temperature of 100° C. for 6 hours to obtain a composite material with a fiber content of 60%.

[0070] The matrix resin of this composite material is insoluble in solvents and the carbon fiber cloth cannot be recycled.

[0071] Example 4 (Increasing the amount of phthalic anhydride)

[0072] Step (1) is the same as step (1) of Example 1

[0073] Step (2) uniformly mixes a resveratrol-based epoxy resin (RE), lipoic acid (LA), and phthalic anhydride in a molar ratio of 5:1:5 to form a resin system. Ten layers of 3K carbon fiber plain weave fabric are stacked in a mold, and the resin system is uniformly coated on the fiber surface. The composite material is then hot-pressed and cured at a pressure of 5 MPa and a temperature of 100° C. for 6 hours to produce a composite material having a fiber content of 60%.

[0074] Step (3) 4 g of the composite material prepared above was immersed in 100 mL of a mixed solution of DMF and mercaptoethanol (volume ratio 1:1) and ultrasonically vibrated at 100 Hz for 30 min; the solution was heated to 100° C. and continued to be immersed for 48 hours, then cooled to room temperature, and the carbon fiber cloth was obtained by filtration and separation, washed three times with DMF, and dried in an oven at 100° C. to obtain a recovered carbon fiber plain fabric sample with a recovery rate of 80%.

[0075] Increasing the amount of phthalic anhydride will reduce the solubility of the matrix resin of the composite material in the solvent and the amount of carbon fiber recovered will decrease.

[0076] Example 5 (Increasing the amount of lipoic acid)

[0077] Steps (1) and (3) are the same as those in Example 1.

[0078] Step (2) uniformly mixes a resveratrol-based epoxy resin (RE), lipoic acid (LA), and phthalic anhydride in a molar ratio of 5:2:4 to form a resin system. Ten layers of 3K carbon fiber plain weave fabric are stacked in a mold, and the resin system is uniformly coated on the fiber surface. The composite material is hot-pressed and cured at a pressure of 5 MPa and a temperature of 100° C. for 6 hours to obtain a composite material with a fiber content of 60%.

[0079] The composite material has lower strength than that of Example 1.

[0080] Example 6 (Reducing the amount of phthalic anhydride)

[0081] Steps (1) and (3) are the same as those in Example 1.

[0082] Step (2) uniformly mixes a resveratrol-based epoxy resin (RE), lipoic acid (LA), and phthalic anhydride in a molar ratio of 5:1:3 to form a resin system. Ten layers of 3K carbon fiber plain weave fabric are stacked in a mold, and the resin system is uniformly coated on the fiber surface. The composite material is hot-pressed and cured at a pressure of 5 MPa and a temperature of 100° C. for 6 hours to obtain a composite material with a fiber content of 60%.

[0083] The composite material has lower strength than that of Example 1.

[0084] Example 7 (reducing the amount of lipoic acid)

[0085] Step (1) is the same as step (1) of Example 1

[0086] Step (2) uniformly mixes a resveratrol-based epoxy resin (RE), lipoic acid (LA), and phthalic anhydride in a molar ratio of 5:0.5:4 to form a resin system. Ten layers of 3K carbon fiber plain weave fabric are stacked in a mold, and the resin system is uniformly coated on the fiber surface. The composite material is hot-pressed and cured at a pressure of 5 MPa and a temperature of 100° C. for 6 hours to obtain a composite material with a fiber content of 60%.

[0087] Step (3) 4 g of the composite material prepared above was immersed in 50 mL of a mixed solution of DMF and mercaptoethanol (volume ratio 1:1) and ultrasonically vibrated at 100 Hz for 30 min; the solution was heated to 100° C. and continued to be immersed for 48 hours, then cooled to room temperature, and the carbon fiber cloth was obtained by filtration and separation, washed three times with DMF, and dried in an oven at 100° C. to obtain a recovered carbon fiber plain fabric sample with a recovery rate of 80%.

[0088] As the amount of lipoic acid decreases, the solubility of the matrix resin decreases and the carbon fiber recovery rate decreases.

[0089] Example 8 (Increasing the reaction temperature in step 2)

[0090] Steps (1) and (3) are the same as those in Example 1.

[0091] Step (2) uniformly mixes a resveratrol-based epoxy resin (RE), lipoic acid (LA), and phthalic anhydride in a molar ratio of 5:1:4 to form a resin system. Ten layers of 3K carbon fiber plain weave fabric are stacked in a mold, and the resin system is uniformly coated on the fiber surface. The composite material is then hot-pressed and cured at a pressure of 5 MPa and a temperature of 150° C. for 6 hours to produce a composite material with a fiber content of 60%.

[0092] The composite material has lower strength than that of Example 1.

[0093] Example 9 (Lowering the reaction temperature in step 2)

[0094] Step (1) is the same as step (1) of Example 1

[0095] Step (2) uniformly mixes a resveratrol-based epoxy resin (RE), lipoic acid (LA), and phthalic anhydride in a molar ratio of 5:1:4 to form a resin system. Ten layers of 3K carbon fiber plain weave fabric are stacked in a mold, and the resin system is uniformly applied to the fiber surface. The composite material is then hot-pressed and cured at a pressure of 5 MPa and a temperature of 50° C. for 6 hours to produce a composite material having a fiber content of 60%.

[0096] Step (3) 4 g of the composite material prepared above was immersed in 50 mL of a mixed solution of DMF and mercaptoethanol (volume ratio 1:1) and ultrasonically vibrated at 100 Hz for 30 min; the solution was heated to 100° C. and continued to be immersed for 48 hours, then cooled to room temperature, and the carbon fiber cloth was obtained by filtration and separation, washed three times with DMF, and dried in an oven at 100° C. to obtain a recovered carbon fiber plain fabric sample with a recovery rate of 50%.

[0097] Lowering the reaction temperature will result in incomplete curing of the epoxy system, and the solvent will not be able to completely dissolve the matrix resin, which will reduce the carbon fiber recovery rate.

[0098] Example 10 (Increasing the reaction time of step 2)

[0099] Step (1) is the same as step (1) of Example 1

[0100] Step (2) uniformly mixes a resveratrol-based epoxy resin (RE), lipoic acid (LA), and phthalic anhydride in a molar ratio of 5:1:4 to form a resin system. Ten layers of 3K carbon fiber plain weave fabric are stacked in a mold, and the resin system is uniformly coated on the fiber surface. The composite material is hot-pressed and cured at a pressure of 5 MPa and a temperature of 100° C. for 24 hours to obtain a composite material with a fiber content of 60%.

[0101] Step (3) 4 g of the composite material prepared above was immersed in 50 mL of a mixed solution of DMF and mercaptoethanol (volume ratio 1:1) and ultrasonically vibrated at 100 Hz for 30 min; the solution was heated to 100° C. and continued to be immersed for 48 hours, then cooled to room temperature, and the carbon fiber cloth was obtained by filtration and separation, washed three times with DMF, and dried in an oven at 100° C. to obtain a recovered carbon fiber plain fabric sample with a recovery rate of 50%.

[0102] Increasing the reaction time will partially carbonize the resin and reduce the carbon fiber recovery rate.

[0103] Example 11 (Reducing the reaction time of step 2)

[0104] Step (1) is the same as step (1) of Example 1

[0105] Step (2) uniformly mixes a resveratrol-based epoxy resin (RE), lipoic acid (LA), and phthalic anhydride in a molar ratio of 5:1:4 to form a resin system. Ten layers of 3K carbon fiber plain weave fabric are stacked in a mold, and the resin system is uniformly coated on the fiber surface. The composite material is then hot-pressed and cured at a pressure of 5 MPa and a temperature of 100° C. for 3 hours to produce a composite material having a fiber content of 60%.

[0106] Step (3) 4 g of the composite material prepared above was immersed in 100 mL of a mixed solution of DMF and mercaptoethanol (volume ratio 1:1) and ultrasonically vibrated at 100 Hz for 30 min; the solution was heated to 100° C. and continued to be immersed for 48 hours, then cooled to room temperature, and the carbon fiber cloth was obtained by filtration and separation, washed three times with DMF, and dried in an oven at 100° C. to obtain a recovered carbon fiber plain fabric sample with a recovery rate of 40%.

[0107] Shorten the reaction time, the epoxy system curing reaction is incomplete, and the resin becomes noticeably soft.

[0108] The solvent cannot completely dissolve the matrix resin, and the carbon fiber recovery rate is reduced.

[0109] Example 12 (Increasing the reaction pressure in step 2)

[0110] Steps (1) and (3) are the same as those in Example 1.

[0111] Step (2) uniformly mixes a resveratrol-based epoxy resin (RE), lipoic acid (LA), and phthalic anhydride in a molar ratio of 5:1:4 to form a resin system. Ten layers of 3K carbon fiber plain weave fabric are stacked in a mold, and the resin system is uniformly applied to the fiber surface. The composite material is hot-pressed and cured at a pressure of 10 MPa and a temperature of 100° C. for 6 hours to obtain a composite material with a fiber content of 60%.

[0112] The composite material has lower strength than that of Example 1.

[0113] Example 13 (Reducing the reaction pressure in step 2)

[0114] Step (1) is the same as step (1) of Example 1

[0115] Step (2) uniformly mixes a resveratrol-based epoxy resin (RE), lipoic acid (LA), and phthalic anhydride in a molar ratio of 5:1:4 to form a resin system. Ten layers of 3K carbon fiber plain weave fabric are stacked in a mold, and the resin system is uniformly coated on the fiber surface. The composite material is hot-pressed and cured at a pressure of 1 MPa and a temperature of 100° C. for 6 hours to obtain a composite material with a fiber content of 60%.

[0116] Step (3) 4 g of the composite material prepared above was immersed in 50 mL of a mixed solution of DMF and mercaptoethanol (volume ratio 1:1) and ultrasonically vibrated at 100 Hz for 30 min; the solution was heated to 100° C. and continued to be immersed for 48 hours, then cooled to room temperature, and the carbon fiber cloth was obtained by filtration and separation, washed three times with DMF, and dried in an oven at 100° C. to obtain a recovered carbon fiber plain fabric sample with a recovery rate of 50%.

[0117] Lowering the reaction pressure will cause incomplete curing reaction of the epoxy system and the resin will become noticeably soft.

[0118] The solvent cannot completely dissolve the matrix resin, and the carbon fiber recovery rate is reduced.

[0119] Example 14

[0120] Step (1) is the same as step (1) of Example 1

[0121] In step (2), resveratrol-based epoxy resin (RE) and amine curing agent are evenly coated on the fiber surface, and hot-pressed and cured at a pressure of 5 MPa and a temperature of 100° C. for 6 hours to obtain a composite material that cannot be recycled.

Claims

1. A recyclable resveratrol-based epoxy Vitrimers, characterized by: Resveratrol-based epoxy resin is used as the base, and all or part of the epoxy groups on it are esterified; The esterified groups include some ester groups containing disulfide bonds.

2. The recyclable resveratrol-based epoxy vitrimers according to claim 1, characterized in that: It is a network compound having a monomeric structure as shown in the following structure: n＝1-5。 3. A method for preparing recyclable resveratrol-based epoxy vitrimers according to any one of claims 1-2, characterized in that: Using the natural polyphenol compound resveratrol as raw material, a bio-based epoxy resin with a branched structure is constructed through its multifunctional properties; Among them, an acid containing a dynamic disulfide bond is used to form a dynamic bond with an epoxy group to regulate the dynamic exchange properties of epoxy Vitrimers; The mechanical strength of epoxy Vitrimers is regulated by curing reaction between natural polycarboxylic acids / anhydrides and epoxy groups.

4. A composite material for use in the manufacture of carbon fiber composite materials, characterized in that: Contains resin system; The resin system comprises a resveratrol-based epoxy resin, an acid containing a dynamic disulfide bond, and a polyacid or anhydride.

5. A composite material for manufacturing carbon fiber composite materials according to claim 4, characterized in that: The molar ratio of the resveratrol-based epoxy resin, the acid containing a dynamic disulfide bond and the polyacid or anhydride is 5:0.5-10:3-10.

6. The composite material for manufacturing carbon fiber composite materials according to claim 4, characterized in that: The preparation method of the resveratrol-based epoxy resin comprises reacting resveratrol with epichlorohydrin under alkaline conditions at 80-150° C. for 5-8 hours to prepare the resveratrol-based epoxy resin with an epoxy value of 0.4-0.

6.

7. The method for preparing a carbon fiber composite material according to any one of claims 4 to 6, wherein: The resveratrol-based epoxy resin, the acid containing a dynamic disulfide bond, and the polyacid or acid anhydride are uniformly mixed to form a resin system; After the resin system is evenly applied to the carbon fiber laminate, it is placed in a hot pressing mold and hot-pressed and cured at a temperature of 80-150°C under a pressure of 2-10 MPa. The curing time is maintained at 4-10 hours to obtain a Vitrimers epoxy resin-based carbon fiber composite material.

8. A method for recycling carbon fiber composite materials according to any one of claims 4 to 6, characterized in that: The carbon fiber composite material is immersed in a mixed solution of DMF and mercaptoethanol and ultrasonically vibrated for 0.5-1 hour; the solution is heated to 80-120°C and soaked for 24-48 hours, then cooled to room temperature, and the carbon fiber cloth is obtained by filtration separation. After washing with DMF, the recovered carbon fiber plain fabric sample is obtained after drying in an oven.

9. The method for recycling carbon fiber composite materials according to claim 8, wherein: The volume ratio of DMF to mercaptoethanol is 1-5:0-5.

10. The method for recycling carbon fiber composite materials according to claim 8, wherein: The carbon fiber composite material and the mixed solution are used in an amount of 10-20 mL of the mixed solution per gram of the carbon fiber composite material.

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