Process for the preparation of bio-based epoxy resin / carbon fiber composites

Abstract

The present application relates to the technical field of high polymer composite material, and particularly relates to a preparation method of a bio-based epoxy resin / carbon fiber composite material.The specific preparation process is as follows: (1) synthesizing a bio-based end mercapto hyperbranched polymer containing hexahydro-sym-triazine and a hyperbranched epoxy resin; (2) preparing a bio-based epoxy resin by mechanically blending a bio-based hyperbranched epoxy resin and a bio-based linear epoxy resin; (3) infiltrating the bio-based mixed resin into chemically treated carbon fibers, and then laminating and compounding, so that a bio-based epoxy resin / carbon fiber composite material with high strength and high modulus is obtained.The bio-based epoxy resin / carbon fiber composite material can be completely degraded in an acidic hydrogen peroxide solution, so that the carbon fibers can be recycled and reused.The present application has the characteristics of simple process, high strength, high modulus, degradability and recyclability, and can be used in the fields of power cables, aerospace and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer composite materials, in particular to a preparation method of a bio-based epoxy resin / carbon fiber composite material. BACKGROUND

[0002] Carbon fiber reinforced thermosetting polymer composites have high specific strength, excellent mechanical properties, chemical corrosion resistance and other advantages, and are increasingly widely used in the fields of aerospace, power cables, wind power generation, etc. However, most thermosetting resins such as bisphenol A type epoxy resins are produced from petroleum raw materials. With the rising price of fossil fuels, the demand for health and environmental protection, and the potential of bio-based resources to produce thermosetting materials with performance comparable to petroleum-based materials (ACS Sustainable Chem. Eng. 2016, 4, 4328-4339), how to replace petroleum-based epoxy resins with thermosetting resins synthesized from bio-based resources has attracted more and more attention from researchers.

[0003] The applicant team previously prepared a degradable hyperbranched epoxy resin (patent ZL201810386063.3, ZL201810387204.3) and a degradable bio-based hyperbranched epoxy resin (patent ZL202010396471.4, ZL201611044769.9) for reinforcing and toughening bisphenol A type epoxy resins, but bisphenol A type epoxy resins have physiological toxicity and are derived from petroleum. To solve this problem, the applicant team previously prepared a bio-based linear epoxy resin (patent ZL202111664373.5). Therefore, developing bio-based resources as the basis for synthesizing bio-based hyperbranched epoxy resins and bio-based linear epoxy resins, and using them to prepare carbon fiber composites is a fundamental way to solve the problems in this field. SUMMARY

[0004] In view of the above problems existing in the prior art, the present application provides a hexahydro-sym-triazine bio-based hyperbranched epoxy resin-carbon fiber composite material and a preparation method thereof.

[0005] The present application solves the above technical problems by the following technical solutions:

[0006] One of the technical solutions: a hexahydro-sym-triazine bio-based hyperbranched epoxy resin, the structural formula of which is shown in general formula (1):

[0007]

[0008] wherein the structure of R is as follows:

[0009]

[0010] Where n is a natural number from 1 to 5; mercaptoalkyl acids and alcohols undergo esterification to form -COO- from -CO- and -O-; thiols and olefin compounds undergo thiol-olefin click reactions to form -CS- with one of -R', -R”, or -R”' to form -CS-R'(R”,R”').

[0011] Where R', R”, and R”' are the same or different, and are independently represented by the structure of general formula (2), general formula (3), or general formula (4):

[0012]

[0013] General formula (2) General formula (3) General formula (4)

[0014] Where X can be one or more of the following structures:

[0015]

[0016] The structure of R1 is as follows:

[0017]

[0018] The structure of R2 is as follows:

[0019]

[0020] R3 can be one or more of the following structures:

[0021]

[0022] The number-average molecular weight of the hexahydrotriazine-containing bio-based hyperbranched epoxy resin is 2000–28000 g / mol, and the epoxy value is 0.09–0.19 mol / 100g.

[0023] Technical Solution Two: A method for preparing a hexahydrotriazine-containing bio-based hyperbranched epoxy resin, comprising the following steps:

[0024] Bio-based diamine and maleic anhydride were mixed uniformly in a dehydrating agent, and a catalyst was added under a nitrogen atmosphere. The mixture was stirred at 110-160°C for 8-16 hours. After precipitation in an ice-water bath and filtration of the solid, a bio-based bismaleimide monomer was obtained. Phenylenetetrazol, an aldehyde compound, and a mercaptoalkyl acid were mixed uniformly in an organic solvent and stirred under a nitrogen atmosphere at 25-100°C for 4-16 hours. The organic solvent was removed by rotary evaporation to obtain a bio-based hexahydropyridine monomer. The bio-based bismaleimide monomer, the bio-based hexahydropyridine monomer, and the organic solvent were then reacted using a power of 4... A hyperbranched polymer with terminal thiol groups was obtained by clicking reaction under a photoinitiator with ultraviolet light of 00W-800W for 30-100min, with a number average molecular weight of 1600-26000g / mol. Then, an alkenyl epoxy compound was added and the reaction was carried out by clicking reaction under ultraviolet light of 400W-800W for 60-120min. The organic solvent was removed by rotary evaporation, and a bio-based hyperbranched epoxy resin containing hexahydrotriazine was obtained, with a number average molecular weight of 2000-28000g / mol and an epoxy value of 0.09-0.19mol / 100g.

[0025] The molar ratio of the bio-based diamine to maleic anhydride is 1:(2.10-2.50); ​​the molar ratio of the phenylglycine, aldehyde compound, and mercaptoalkyl acid is 1:(1-2):(1-2); the molar ratio of the bio-based bismaleimide to the bio-based hexahydrotriazine is 1:(1.05-2); the molar ratio of the bio-based hexahydrotriazine monomer to the alkenyl epoxy compound is 1:(1.09-2).

[0026] The bio-based diamine is one or more selected from 2,5-furandimethylamine, 1,4-cyclohexanedimethylamine, and isoflavonediamine; the mercaptoalkyl acid is HS(CH2). n COOH, where n is a natural number from 1 to 5; the aldehyde compound is one or more of formaldehyde aqueous solution, trioxymethylene, and paraoxymethylene (degree of polymerization n is a natural number from 2 to 100); the alkenyl epoxy compound is one or more of 1,2-epoxy-5-hexene, allyl glycidyl ether, and 2,3-epoxypropyl acrylate.

[0027] The dehydrating agent is one or more of toluene, benzene, 1,4-dioxane, xylene, and N,N-dimethylformamide, and the added dehydrating agent is 5-15 times the mass of maleic anhydride; the catalyst is one or more of titanate, tetraisopropyl titanate, or p-toluenesulfonic acid, and the added catalyst is 1.5-3.0% of the mass of maleic anhydride; the organic solvent for synthesizing the bio-based hexahydrotriazine monomer is one or more of acetone, chloroform, ethyl acetate, dichloromethane, tetrahydrofuran, toluene, xylene, and 1,4-dioxane, and the added organic solvent is 5-18 times the mass of phenylglycine; The photoinitiator is one or more of p-aminophenylacetone, 1-hydroxycyclohexylacetone, 4-dimethylaminopyridine, benzophenone, 2,2-dimethoxy-2-phenylacetophenone, and 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholino)-1-propanone, and the mass of the added photoinitiator is 1.0-3.5% of the mass of the bio-based hexahydrotriazine; the organic solvent for synthesizing the terminal thiol hyperbranched polymer is one or more of dichloromethane, tetrahydrofuran, water, N,N-dimethylformamide, xylene, toluene, and 1,4-dioxane, and the mass of the added organic solvent is 2-5 times the mass of the bio-based hexahydrotriazine monomer.

[0028] Technical Solution Three: A bio-based epoxy resin composite material, the composite material comprising the above-mentioned hexahydrotriazine-containing bio-based hyperbranched epoxy resin and bio-based linear epoxy resin. The bio-based linear epoxy resin has an epoxy value of 0.10–0.90 mol / 100g, preferably 0.48–0.55 mol / 100g.

[0029] The composite material is obtained by uniformly mixing a hexahydrotriazine-containing bio-based hyperbranched epoxy resin, a bio-based linear epoxy resin, and a curing agent, and then pouring the mixture into a mold for thermosetting. The curing temperature is 50-200℃, and the curing time is 4-8h. The curing agent is one or more of 4,4'-methylenedicyclohexylamine, 4,4'-diaminodiphenylmethane, diethylenetriamine, isophorone diamine (IPDA), 2,2'-diaminodiphenyl sulfide (DOA), and 4,4'-diaminodiphenyl sulfide (BAS).

[0030] The mass ratio of the hexahydrotriazine-containing bio-based hyperbranched epoxy resin to the bio-based linear epoxy resin is (0.5-1):(9-9.5). The mass of the added curing agent is calculated using the following formula: n * molecular weight of the curing agent * epoxy value of the epoxy resin in the system * mass of the epoxy resin in the system / number of active hydrogens on the curing agent, where n = 0.01-0.02.

[0031] Technical Solution 4: A bio-based epoxy resin / carbon fiber composite material, wherein the composite material is prepared by blending the above-mentioned hexahydrotriazine-containing bio-based hyperbranched epoxy resin or the hexahydrotriazine-containing bio-based hyperbranched epoxy resin prepared by the above method with a bio-based linear epoxy resin and filling it into carbon fiber cloth, and then laminating and curing it; before curing, the carbon fiber cloth is modified by thiol-olefin click reaction with the terminal thiol hyperbranched polymer prepared by the above method to obtain surface-functionalized carbon fiber cloth.

[0032] Furthermore, the preparation method includes the following steps: immersing carbon fiber cloth in a mixed solution of the terminal thiol hyperbranched polymer, organic solvent, and photoinitiator prepared by the above method, and performing a thiol-olefin click reaction for 40-80 minutes under the action of the photoinitiator using ultraviolet light with a power of 400W-800W; after the reaction is completed, removing the carbon fiber cloth and drying it at 50-80℃ for 8-24 hours to obtain surface-functionalized carbon fiber cloth; placing the surface-functionalized carbon fiber cloth into a mold, uniformly coating the above-mentioned hexahydrotriazine-containing bio-based hyperbranched epoxy resin or the hexahydrotriazine-containing bio-based hyperbranched epoxy resin prepared by the above method, a bio-based linear epoxy resin, and a curing agent onto the surface-functionalized carbon fiber cloth, and hot-pressing curing at 1-10MPa and 80-180℃ for 3-6 hours, cooling to room temperature and removing it to obtain the bio-based epoxy resin / carbon fiber composite material.

[0033] The mass ratio of the carbon fiber cloth to the terminal thiol hyperbranched polymer is 1:(0.50-0.83); the mass ratio of the surface-functionalized carbon fiber cloth, the hexahydrotriazine-containing bio-based hyperbranched epoxy resin, and the bio-based linear epoxy resin is (0.90-0.95):(0.01-0.05):(0.45-0.50).

[0034] The carbon fiber cloth is one of commercially available T300, T700, and T800; the photoinitiator is one or more of p-aminophenylacetone, 4-dimethylaminopyridine, benzophenone, 1-hydroxycyclohexylacetone, 2,2-dimethoxy-2-phenylacetophenone, and 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone, and the added photoinitiator accounts for 1.0-3.5% of the mass of the carbon fiber cloth; the organic solvent is tetrahydrofuran, 1,4-dioxane, ethyl acetate, anhydrous ethanol, methanol, dimethyl sulfoxide, toluene, etc. One or more of toluene, acetone, chloroform, N,N-dimethylformamide, and dichloromethane are used, with a mass of 5 to 30 times that of the carbon fiber cloth. The curing agent is one or more of 4,4'-methylenedicyclohexylamine, 4,4'-diaminodiphenylmethane, diethylenetriamine, isofluranediamine, 2,2'-diaminodiphenyl sulfide, and 4,4'-diaminodiphenyl sulfide. The mass of the added curing agent is calculated using the following formula: n * molecular weight of the curing agent * epoxy value of the epoxy resin in the system * mass of the epoxy resin in the system / number of active hydrogens on the curing agent, where n = 0.01-0.02.

[0035] Technical Solution 5: A method for degrading and recycling a bio-based epoxy resin / carbon fiber composite material, comprising the following steps: immersing the above-mentioned bio-based epoxy resin / carbon fiber composite material in an acidic hydrogen peroxide solution, degrading it at 60-80℃ for 6-12 hours to obtain carbon fiber cloth and degradation solution; washing the carbon fiber cloth with acetone and drying it at 50-70℃ for 10-24 hours to obtain recycled carbon fiber cloth; then replacing the original carbon fiber cloth with the recycled carbon fiber cloth for recycling.

[0036] The acidic hydrogen peroxide solution is a hydrogen peroxide solution of phosphoric acid or hydrochloric acid, with an acid concentration of 0.10-1.00 mol / L. The solvent in the acidic hydrogen peroxide solution is one or more of tetrahydrofuran, 1,4-dioxane, acetone, water, and N,N-dimethylformamide. The mass percentage of hydrogen peroxide in the acidic hydrogen peroxide solution is 50%-90%. The mass ratio of the bio-based epoxy resin / carbon fiber composite material to the acidic hydrogen peroxide solution is 1:(2-5).

[0037] Compared with the prior art, the technical solution of the present invention has the following advantages and beneficial effects:

[0038] (1) The present invention introduces a biodegradable hexahydrotriazine structure and an imide bond into the structure of hyperbranched epoxy resin to achieve the biodegradable function of epoxy resin after curing.

[0039] (2) The bio-based hyperbranched epoxy resin of the present invention has the advantages of hyperbranched polymers and has obvious reinforcing and toughening functions for bio-based linear epoxy resins. It is expected to be widely used in the field of epoxy resin reinforcement and toughening.

[0040] (3) The preparation process of the bio-based hyperbranched epoxy resin / bio-based linear epoxy resin composite material of the present invention is simple, the reaction conditions are relatively mild, the reaction time is short, and the raw material cost is low.

[0041] (4) The bio-based epoxy resin / carbon fiber composite material of the present invention has the characteristics of high strength and high modulus, and is expected to be used in power cables, aerospace and other fields;

[0042] (5) The preparation process of the bio-based epoxy resin / carbon fiber composite material of the present invention is simple, the reaction conditions are relatively mild, the reaction time is short, and the raw material cost is low. Attached Figure Description

[0043] Figure 1 The infrared spectra of the hexahydrotriazine-containing bio-based hyperbranched epoxy resins prepared in Examples 7-9 are shown. The value at 2966 cm⁻¹ is also shown. -1 The absorption peak at 1725 cm⁻¹ is attributed to -CH₂-. -1 The absorption peak at 1692 cm⁻¹ is attributed to the stretching vibration of -C=ON-. -1 The absorption peak at 1383 cm⁻¹ is attributed to the stretching vibration of -C = OO⁻. -1 The absorption peak at 925 cm⁻¹ is attributed to the -CN- absorption peak. -1 The absorption peak at that point is the absorption peak of the epoxy group. Detailed Implementation

[0044] The method of the present invention will be further described below with reference to specific embodiments, but these embodiments should not limit the scope of protection of the present invention in any way.

[0045] The carbon fiber cloth used in the examples and comparative examples is one of the commercially available T300, T700 and T800. T300 was purchased from Anqing Kawei Technology Co., Ltd. with specification KCF220T, T700 was purchased from Anqing Kawei Technology Co., Ltd. with specification KCF200T, and T800 was purchased from Anqing Kawei Technology Co., Ltd. with specification KCF260T.

[0046] The bio-based basic epoxy resin used in the examples is any one of diglycidyl furanate dicarboxylate ether (DGF), ferulic acid-based epoxy resin (FEP), and vanillyl alcohol-based bio-epoxy resin (DGEVA). Specifically, diglycidyl furanate dicarboxylate ether (DGF) was prepared according to RSC Adv., 2015, 5, 15930, with a number-average molecular weight of 266.08 g / mol and an epoxy value of 0.48 mol / 100 g; ferulic acid-based epoxy resin (FEP) was prepared according to patent ZL202111664373.5, with a number-average molecular weight of 306.11 g / mol and an epoxy value of 0.51 mol / 100 g; and vanillyl alcohol-based bio-epoxy resin (DGEVA) was prepared according to ACSSustainable. Prepared according to Chem.Eng.2020,8,11215-11223, with a number average molecular weight of 266.12 g / mol and an epoxy value of 0.55 mol / 100 g.

[0047] The number-average molecular weight was obtained by gel permeation chromatography (GPC), based on the permeation behavior of hyperbranched polymers in gel, by measuring the ratio of permeation time to standard sample; the epoxy value was obtained by the hydrochloric acid-acetone method, using hydrochloric acid to react with epoxy groups, then titrating to determine the amount of remaining hydrochloric acid, thus knowing the amount of hydrochloric acid that reacted with the epoxy groups, and calculating the amount of epoxy groups to obtain the epoxy value.

[0048] Example 1: A bio-based epoxy resin-carbon fiber composite material and its preparation method, the steps of which are as follows:

[0049] (1) Synthesis of bio-based hyperbranched epoxy resin containing hexahydrotriazine

[0050] 0.10 mol (12.61 g) of 2,5-furandimethylamine and 0.25 mol (24.52 g) of maleic anhydride were mixed thoroughly in 63.05 g of xylene and 63.05 g of 1,4-dioxane. 0.39 g of p-toluenesulfonic acid was added under a nitrogen atmosphere, and the mixture was stirred at 110 °C for 16 h. After precipitation in an ice-water bath for 12 h, the mixture was filtered, and the solid was a bio-based bismaleimide monomer. 0.10 mol (13.71 g) of phenylglycine, 0.10 mol (8.12 g, 37%) of formaldehyde aqueous solution, and 0.15 mol (15.90 g) of mercaptopropionic acid were mixed thoroughly in 68.55 g of dichloromethane and 68.55 g of tetrahydrofuran. The mixture was stirred at 25 °C under a nitrogen atmosphere for 16 h. The organic solvent was removed by rotary evaporation to obtain a bio-based hexahydrotriazine monomer. 0.14 g of... 0.01 mol (2.86 g) of bio-based bismaleimide monomer, 0.02 mol (14.24 g) of bio-based hexahydrotriazine monomer, and 28.48 g of 1,4-dioxane were reacted with 1-hydroxycyclohexylphenyl ketone under UV light for 100 min to obtain a terminal thiol hyperbranched polymer (BISPI-4). Then, 0.04 mol (3.93 g) of 1,2-epoxy-5-hexene was added and reacted with 1,4-dioxane under UV light for 120 min. The 1,4-dioxane was removed by rotary evaporation, yielding a hexahydrotriazine-containing bio-based hyperbranched epoxy resin (BIEP-4). GPC analysis showed its molecular weight to be approximately 2133 g / mol, and titration yielded an epoxy value of 0.19 mol / 100 g. The results are shown in Tables 1 and 2.

[0051] (2) Performance Study of Bio-based Epoxy Resins

[0052] First, 1.40g of diethylenetriamine, 9.25g of diglycidyl furanate dimethyl ether (DGF) and 0.75g of BIEP-4 were mixed in an oil bath at 120℃ for 1 hour until homogeneous. Then, the mixture was poured into a 10×80mm mold and cured at 80℃ for 1 hour, 130℃ for 1 hour, and 170℃ for 2 hours to obtain the BIEP-4 / DGF composite resin. The mechanical properties of the composite resin were tested using a universal testing machine, and the results are shown in Table 3.

[0053] (3) Preparation of bio-based epoxy resin-carbon fiber composite materials

[0054] 3.00 g of carbon fiber cloth (T300) was completely immersed in a mixed solution of 1.50 g of thiol-terminated bio-based hyperbranched polymer (BISPI-4), 15 g of ethyl acetate, and 0.03 g of p-aminophenylacetone. The solution was then irradiated with 400 W of ultraviolet light for 80 min to induce a thiol-olefin click reaction, yielding surface-functionalized carbon fiber cloth, 1-TCF. The 1-TCF was removed and dried at 50 °C for 24 h. 3.00 g of the dried 1-TCF was placed in a mold, and a mixture of 1.39 g of DGF, 0.11 g of BIEP-4, and 0.21 g of diethylenetriamine was uniformly coated onto the 1-TCF in the mold. The mixture was then hot-pressed at 120 °C for 4 h at 3 MPa. After hot pressing, the mixture was cooled to room temperature and removed to obtain the bio-based epoxy resin-carbon fiber composite material. The mechanical properties of the composite material were tested using a universal testing machine; its tensile strength and flexural strength are shown in Table 4.

[0055] (4) Degradation and recycling of bio-based epoxy resin-carbon fiber composites

[0056] 4.00 g of bio-based epoxy resin-carbon fiber composite material was immersed in 20.00 g of 1.00 mol / L phosphoric acid in a hydrogen peroxide-acetone solution (hydrogen peroxide:acetone = 9:1, m / m), and degraded at 80 °C for 6 h to obtain carbon fiber cloth and degradation solution. The carbon fiber cloth was washed with acetone and dried at 70 °C for 10 h to obtain regenerated carbon fiber cloth. Then, 3.00 g of the regenerated carbon fiber cloth was completely immersed in a mixed solution of 1.50 g of thiol-terminated bio-based hyperbranched polymer (BISPI-4), 15 g of ethyl acetate and 0.03 g of p-aminophenylacetone, and irradiated with 400 W of ultraviolet light for 80 min to carry out a thiol-olefin click reaction to obtain surface-functionalized carbon fiber cloth, i.e., 1-rTCF. The 1-rTCF was removed and dried at 50 °C for 24 h. 3.00 g of the dried 1-rTCF was placed in a mold, and 1.39 g of DGF and 0.11 g of... A mixture of BIEP-4 and 0.21g of diethylenetriamine was uniformly coated onto 1-rTCF in a mold and hot-pressed at 120℃ for 4 hours under 3MPa conditions. After hot pressing, the mixture was cooled to room temperature and removed to obtain a bio-based epoxy resin-carbon fiber composite material. The mechanical properties of the composite material were tested using a universal testing machine, and its tensile strength is shown in Table 4.

[0057] Example 2: A bio-based epoxy resin-carbon fiber composite material and its preparation method, the steps of which are as follows:

[0058] (1) Synthesis of bio-based hyperbranched epoxy resin containing hexahydrotriazine

[0059] 0.10 mol (12.61 g) of 2,5-furandimethylamine and 0.23 mol (22.55 g) of maleic anhydride were mixed thoroughly with 120.61 g of benzene and 120.61 g of N,N-dimethylformamide. Under a nitrogen atmosphere, 0.26 g of n-butyl titanate and 0.26 g of tetraisopropyl titanate were added, and the mixture was stirred at 160 °C for 8 h. After precipitation in an ice-water bath for 18 h, the solid was filtered to obtain bio-based bismaleimide. Imine monomer; 0.10 mol (13.71 g) phenylglycine, 0.15 mol (12.17 g, 37%) formaldehyde aqueous solution and 0.15 mol (15.90 g) mercaptopropionic acid were mixed evenly in 123.39 g acetone and 123.39 g chloroform, and stirred at 100 °C for 4 h under a nitrogen atmosphere. The organic solvent was removed by rotary evaporation to obtain a bio-based hexahydrotriazine monomer; in 0.07 g A thiol-terminated hyperbranched polymer (BISPI-6) was obtained by clicking reaction of 0.01 mol (2.86 g) of bio-based bismaleimide monomer, 0.013 mol (7.25 g) of bio-based hexahydrotriazine monomer, and 21.75 g of N,N-dimethylformamide under 800 W UV light for 30 min with 1-hydroxycyclohexyl benzophenone and 0.07 g p-aminoacetone. Then, 0.02 mol (2.56 g) of 2,3-epoxypropyl acrylate was added and the reaction was carried out under 800 W UV light for 60 min. The N,N-dimethylformamide was removed by rotary evaporation, yielding a hexahydrotriazine-containing bio-based hyperbranched epoxy resin (BIEP-6). GPC analysis showed its molecular weight to be approximately 4568 g / mol, and titration yielded an epoxy value of 0.13 mol / 100 g. The results are shown in Tables 1 and 2.

[0060] (2) Performance Study of Bio-based Epoxy Resins

[0061] First, 0.50g of BIEP-6, 3.08g of 4,4'-methylenebiscyclohexylamine, and 9.50g of DGF were mixed in an oil bath at 120℃ for 1 hour until homogeneous. Then, the mixture was poured into a 10×80mm mold and cured at 50℃ for 1 hour, 130℃ for 1 hour, 170℃ for 2 hours, and 180℃ for 2 hours to obtain the BIEP-6 / DGF composite resin. The mechanical properties of the composite resin were tested using a universal testing machine, and the results are shown in Table 3.

[0062] (3) Preparation of bio-based epoxy resin-carbon fiber composite materials

[0063] 3.00g of carbon fiber cloth (T700) was completely immersed in a mixed solution of 2.00g of thiol-terminated bio-based hyperbranched polymer (BISPI-6), 20g of N,N-dimethylformamide, 15g of tetrahydrofuran, 15g of 1,4-dioxane, 0.03g of p-aminophenylacetone, and 0.03g of 1-hydroxycyclohexylacetone. The solution was irradiated with 400W ultraviolet light for 80min to carry out a thiol-olefin click reaction, obtaining surface-functionalized carbon fiber cloth, i.e., 2-TCF. The 2-TCF was then removed and dried at 70℃ for 18h. 3.00g of the dried 2-TCF was placed in a mold, and 1.425g of DGF, 0.075g of BISPI-6, and 0.46g of... The mixture of 4,4'-methylene dicyclohexylamine was uniformly coated onto 2-TCF in a mold and cured by hot pressing at 80°C for 3 hours under 1 MPa conditions, followed by hot pressing at 120°C for 3 hours. After hot pressing, the mixture was cooled to room temperature and removed to obtain the bio-based epoxy resin-carbon fiber composite material. The mechanical properties of the composite material were tested using a universal testing machine, and its tensile strength and flexural strength are shown in Table 4.

[0064] (4) Degradation and recycling of bio-based epoxy resin-carbon fiber composites

[0065] 4.00 g of bio-based epoxy resin-carbon fiber composite material was immersed in 8.00 g of 0.10 mol / L phosphoric acid in a hydrogen peroxide-tetrahydrofuran solution (hydrogen peroxide:tetrahydrofuran = 5:5, m / m), and degraded at 60 °C for 12 h to obtain carbon fiber cloth and degradation solution. The carbon fiber cloth was washed with acetone and dried at 50 °C for 24 h to obtain recycled carbon fiber cloth. Then, 3.00 g of recycled carbon fiber cloth was completely immersed in 2.00 g of BISPI-6 (prepared in Example 2), 20 g of N,N-dimethylformamide, 15 g of tetrahydrofuran, and 15 g of... A thiol-olefin click reaction was carried out in a mixed solution of 1,4-dioxane, 0.03 g p-aminophenylacetone, and 0.03 g 1-hydroxycyclohexylacetone under 400 W ultraviolet light for 80 min to obtain surface-functionalized carbon fiber cloth, namely 2-rTCF. The 2-rTCF was removed and dried at 70 °C for 18 h. 3.00 g of the dried 2-rTCF was placed in a mold, and a mixture of 1.425 g DGF, 0.075 g BIEP-6, and 0.46 g 4,4'-methylenebiscyclohexylamine was uniformly coated on the 2-rTCF in the mold. The mixture was hot-pressed and cured at 80 °C for 3 h at 1 MPa and then at 120 °C for 3 h. After the hot pressing was completed, the mixture was cooled to room temperature and removed to obtain the bio-based epoxy resin-carbon fiber composite material. The mechanical properties of the composite material were tested using a universal testing machine, and its tensile strength is shown in Table 4.

[0066] Example 3: A bio-based epoxy resin-carbon fiber composite material and its preparation method, the steps of which are as follows:

[0067] (1) Synthesis of bio-based hyperbranched epoxy resin containing hexahydrotriazine

[0068] 0.10 mol (12.61 g) of 2,5-furandimethylamine and 0.25 mol (24.52 g) of maleic anhydride were mixed thoroughly in 122.60 g of toluene and 122.60 g of N,N-dimethylformamide. Under a nitrogen atmosphere, 0.32 g of p-toluenesulfonic acid and 0.32 g of n-butyl titanate were added, and the mixture was stirred at 135 °C for 12 h. After precipitation in an ice-water bath for 24 h, the solid was filtered to obtain a bio-based bismaleimide monomer. 0.10 mol (13.71 g) of phenylglycine, 0.20 mol (12.00 g) of paraformaldehyde (degree of polymerization 2), and 0.10 mol (14.80 g) of mercaptohexanoic acid were mixed thoroughly in 164.52 g of ethyl acetate. Under a nitrogen atmosphere, the mixture was stirred at 60 °C for 10 h. The organic solvent was removed by rotary evaporation to obtain a bio-based hexahydrotriazine monomer. 0.26 g of... 0.01 mol (2.86 g) of bio-based bismaleimide monomer, 0.0105 mol (8.80 g) of bio-based hexahydrotriazine monomer, and 37.40 g of dichloromethane were reacted under UV light at 600 W for 60 min to obtain a terminal thiol hyperbranched polymer (BISPI-24). Then, 0.0114 mol (1.30 g) of allyl glycidyl ether was added and reacted under UV light at 600 W for 80 min. Dichloromethane was removed by rotary evaporation to obtain a hexahydrotriazine-containing bio-based hyperbranched epoxy resin (BIEP-24). GPC analysis showed that its molecular weight was approximately 26000 g / mol, and the titrated epoxy value was 0.09 mol / 100 g. The results are shown in Tables 1 and 2.

[0069] (2) Performance Study of Bio-based Epoxy Resins

[0070] First, 1.00g of BIEP-24, 2.57g of 4,4'-diaminodiphenylmethane, and 9.00g of DGF were mixed in an oil bath at 125℃ for 2 hours until homogeneous. Then, the mixture was poured into a 10×80mm mold and cured at 60℃ for 1 hour, 80℃ for 3 hours, 130℃ for 1 hour, 170℃ for 2 hours, and 200℃ for 1 hour to obtain the BIEP-24 / DGF composite resin. The mechanical properties of the composite resin were tested using a universal testing machine, and the results are shown in Table 3.

[0071] (3) Preparation of bio-based epoxy resin-carbon fiber composite materials

[0072] 3.00g of carbon fiber cloth (T800) was completely immersed in a mixed solution of 2.50g of thiol-terminated bio-based hyperbranched polymer (BISPI-24), 30g of acetone, 30g of chloroform, 30g of dichloromethane, and 0.10g of 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone. The solution was then irradiated with 600W ultraviolet light for 60min to induce a thiol-olefin click reaction, yielding surface-functionalized carbon fiber cloth, i.e., 3-TCF. The 3-TCF was removed and dried at 80℃ for 8h. 3.00g of the dried 3-TCF was placed in a mold, and 1.35g of DGF, 0.15g of BISPI-24, and 0.44g of... A mixture of 4,4'-diaminodiphenylmethane was uniformly coated onto 3-TCF in a mold and hot-pressed at 120°C for 3 hours under 10 MPa conditions. After hot pressing, the mixture was cooled to room temperature and removed to obtain a bio-based epoxy resin-carbon fiber composite material. The mechanical properties of the composite material were tested using a universal testing machine, and its tensile strength and flexural strength are shown in Table 4.

[0073] (4) Degradation and recycling of bio-based epoxy resin-carbon fiber composites

[0074] 4.00 g of bio-based epoxy resin-carbon fiber composite material was immersed in 12.00 g of 0.50 mol / L phosphoric acid in a hydrogen peroxide-N,N-dimethylformamide solution (hydrogen peroxide:N,N-dimethylformamide = 6:4, m / m). After degradation at 70 °C for 8 h, carbon fiber cloth and degradation solution were obtained. The carbon fiber cloth was washed with acetone and dried at 60 °C for 20 h to obtain recycled carbon fiber cloth. Then, 3.00 g of recycled carbon fiber cloth was completely immersed in 2.50 g of thiol-terminated bio-based hyperbranched polymer (BISPI-24), 30 g of acetone, 30 g of chloroform, 30 g of dichloromethane, and 0.10 g of... A thiol-olefin click reaction was carried out in a mixed solution of 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone under 600W ultraviolet light for 60 min to obtain surface-functionalized carbon fiber cloth, namely 3-rTCF. The 3-rTCF was removed and dried at 80℃ for 8 h. 3.00 g of the dried 3-rTCF was placed in a mold, and a mixture of 1.35 g DGF, 0.15 g BIEP-24 and 0.44 g 4,4'-diaminodiphenylmethane was uniformly coated on the 3-rTCF in the mold. The mixture was hot-pressed and cured at 120℃ for 3 h under 10 MPa. After the hot pressing was completed, the mixture was cooled to room temperature and removed to obtain the bio-based epoxy resin-carbon fiber composite material. The mechanical properties of the composite material were tested using a universal testing machine, and its tensile strength is shown in Table 4.

[0075] Example 4: A bio-based epoxy resin-carbon fiber composite material and its preparation method, the steps of which are as follows:

[0076] (1) Synthesis of bio-based hyperbranched epoxy resin containing hexahydrotriazine

[0077] 0.10 mol (14.22 g) of 1,4-cyclohexanedimethylamine and 0.25 mol (24.52 g) of maleic anhydride were mixed thoroughly in 63.05 g of xylene and 63.05 g of 1,4-dioxane. 0.39 g of p-toluenesulfonic acid was added under a nitrogen atmosphere, and the mixture was stirred at 110 °C for 16 h. After precipitation in an ice-water bath for 12 h, the solid was filtered to obtain a bio-based bismaleimide monomer. 0.10 mol (13.71 g) of phenylglycine, 0.10 mol (8.12 g, 37%) of formaldehyde aqueous solution, and 0.15 mol (15.90 g) of mercaptopropionic acid were mixed thoroughly in 68.55 g of dichloromethane and 68.55 g of tetrahydrofuran. The mixture was stirred at 25 °C under a nitrogen atmosphere for 16 h. The organic solvent was removed by rotary evaporation to obtain a bio-based hexahydrotriazine monomer. 0.14 g of... 0.01 mol (3.02 g) of bio-based bismaleimide monomer, 0.02 mol (14.24 g) of bio-based hexahydrotriazine monomer, and 28.48 g of 1,4-dioxane were reacted with 1-hydroxycyclohexylphenyl ketone under UV light for 100 min to obtain a thiol-terminated hyperbranched polymer (BPSPI-4). Then, 0.04 mol (3.93 g) of 1,2-epoxy-5-hexene was added and reacted with 1,4-dioxane under UV light for 120 min. The 1,4-dioxane was removed by rotary evaporation, yielding a hexahydrotriazine-containing bio-based hyperbranched epoxy resin (BPEP-4). GPC analysis showed its molecular weight to be approximately 2054 g / mol, and titration yielded an epoxy value of 0.19 mol / 100 g. The results are shown in Tables 1 and 2.

[0078] (2) Performance Study of Bio-based Epoxy Resins

[0079] First, 1.40g of diethylenetriamine, 9.25g of FEP and 0.75g of BPEP-4 were mixed in an oil bath at 120℃ for 1 hour until homogeneous. Then, the mixture was poured into a 10×80mm mold and cured at 80℃ for 1 hour, 130℃ for 1 hour and 170℃ for 2 hours to obtain the BPEP-4 / FEP composite resin. The mechanical properties of the composite resin were tested using a universal testing machine, and the results are shown in Table 3.

[0080] (3) Preparation of bio-based epoxy resin-carbon fiber composite materials

[0081] 3.00 g of carbon fiber cloth (T300) was completely immersed in a mixed solution of 1.50 g of thiol-terminated bio-based hyperbranched polymer (BPSPI-4), 15 g of ethyl acetate, and 0.03 g of 1-hydroxycyclohexyl benzophenone. The solution was then irradiated with 400 W of ultraviolet light for 80 min to induce a thiol-olefin click reaction, yielding surface-functionalized carbon fiber cloth, 4-TCF. The 4-TCF was removed and dried at 50 °C for 24 h. 3.00 g of the dried 4-TCF was placed in a mold, and a mixture of 1.39 g of FEP, 0.11 g of BPEP-4, and 0.21 g of diethylenetriamine was uniformly coated onto the 4-TCF in the mold. The mixture was then hot-pressed at 120 °C for 4 h at 3 MPa. After hot pressing, the mixture was cooled to room temperature and removed to obtain the bio-based epoxy resin-carbon fiber composite material. The mechanical properties of the composite material were tested using a universal testing machine; its tensile strength and flexural strength are shown in Table 4.

[0082] (4) Degradation and recycling of bio-based epoxy resin-carbon fiber composites

[0083] 4.00 g of bio-based epoxy resin-carbon fiber composite material was immersed in 12.00 g of 0.50 mol / L phosphoric acid in a solution of hydrogen peroxide and 1,4-dioxane (hydrogen peroxide: 1,4-dioxane = 6:4, m / m), and degraded at 70 °C for 8 h to obtain carbon fiber cloth and degradation solution. The carbon fiber cloth was washed with acetone and dried at 60 °C for 20 h to obtain regenerated carbon fiber cloth. Then, 3.00 g of the regenerated carbon fiber cloth was completely immersed in a mixed solution of 1.50 g of thiol-terminated bio-based hyperbranched polymer (BPSPI-4), 15 g of ethyl acetate and 0.03 g of 1-hydroxycyclohexyl benzophenone, and irradiated with 400 W of ultraviolet light for 80 min to carry out a thiol-olefin click reaction to obtain surface-functionalized carbon fiber cloth, i.e., 4-rTCF. The 4-rTCF was removed and dried at 50 °C for 24 h. 3.00 g of the dried material was then... 4-rTCF was placed in a mold, and a mixture of 1.39g FEP, 0.11g BPEP-4 and 0.21g diethylenetriamine was evenly coated onto the 4-rTCF in the mold. The mixture was then hot-pressed and cured at 120℃ for 4 hours under 3MPa. After the hot pressing was completed, the mixture was cooled to room temperature and removed to obtain the bio-based epoxy resin-carbon fiber composite material. The mechanical properties of the composite material were tested using a universal testing machine, and its tensile strength is shown in Table 4.

[0084] Example 5: A bio-based epoxy resin-carbon fiber composite material and its preparation method, the steps of which are as follows:

[0085] (1) Synthesis of bio-based hyperbranched epoxy resin containing hexahydrotriazine

[0086] 0.10 mol (14.22 g) of 1,4-cyclohexanedimethylamine and 0.23 mol (22.55 g) of maleic anhydride were mixed with 120.61 g of benzene and 120.61 g of... N,N-dimethylformamide was mixed thoroughly, and 0.26 g of tetrabutyl titanate and 0.26 g of tetraisopropyl titanate were added under a nitrogen atmosphere. The mixture was stirred at 160 °C for 8 h. After precipitation in an ice-water bath for 15 h, the solid was filtered to obtain a bio-based bismaleimide monomer. 0.10 mol (13.71 g) of phenylglycine, 0.15 mol (12.17 g, 37%) of formaldehyde aqueous solution, and 0.15 mol (15.90 g) of mercaptopropionic acid were mixed thoroughly in 123.39 g of acetone and 123.39 g of chloroform. The mixture was stirred at 100 °C for 4 h under a nitrogen atmosphere. The organic solvent was removed by rotary evaporation to obtain a bio-based hexahydrotriazine monomer. 0.07 g of... A thiol-terminated hyperbranched polymer (BPSPI-6) was obtained by clicking reaction of 0.01 mol (3.02 g) of bio-based bismaleimide monomer, 0.013 mol (7.25 g) of bio-based hexahydrotriazine monomer, and 21.75 g of N,N-dimethylformamide under 800 W UV light for 30 min with 1-hydroxycyclohexyl benzophenone and 0.07 g of p-aminophenylacetone. Then, 0.02 mol (2.56 g) of 2,3-epoxypropyl acrylate was added, and the reaction was carried out under 800 W UV light for 60 min. The N,N-dimethylformamide was removed by rotary evaporation, yielding a hexahydrotriazine-containing bio-based hyperbranched epoxy resin (BPEP-6). GPC analysis showed its molecular weight to be approximately 4400 g / mol, and titration yielded an epoxy value of 0.13 mol / 100 g. The results are shown in Tables 1 and 2.

[0087] (2) Performance Study of Bio-based Epoxy Resins

[0088] First, 0.50g of BPEP-6, 3.08g of 4,4'-methylenebiscyclohexylamine, and 9.50g of FEP were mixed in an oil bath at 120℃ for 1 hour until homogeneous. Then, the mixture was poured into a 10×80mm mold and cured at 50℃ for 1 hour, 130℃ for 1 hour, 170℃ for 2 hours, and 180℃ for 2 hours to obtain the BPEP-6 / FEP composite resin. The mechanical properties of the composite resin were tested using a universal testing machine, and the results are shown in Table 3.

[0089] (3) Preparation of bio-based epoxy resin-carbon fiber composite materials

[0090] 3.00g of carbon fiber cloth (T700) was completely immersed in a mixed solution of 2.00g of thiol-terminated bio-based hyperbranched polymer (BPSPI-6), 20g of N,N-dimethylformamide, 15g of tetrahydrofuran, 15g of 1,4-dioxane, 0.03g of p-aminophenylacetone, and 0.03g of 1-hydroxycyclohexylacetone. The solution was irradiated with 800W ultraviolet light for 40min to carry out a thiol-olefin click reaction, obtaining surface-functionalized carbon fiber cloth, i.e., 5-TCF. The 5-TCF was then removed and dried at 70℃ for 18h. 3.00g of the dried 5-TCF was placed in a mold, and 1.425g of FEP, 0.075g of BPEP-6, and 0.46g of... The mixture of 4,4'-methylene dicyclohexylamine was uniformly coated onto 5-TCF in a mold and cured by hot pressing at 80°C for 3 hours under 1 MPa conditions, followed by hot pressing at 120°C for 3 hours. After hot pressing, the mixture was cooled to room temperature and removed to obtain the bio-based epoxy resin-carbon fiber composite material. The mechanical properties of the composite material were tested using a universal testing machine, and its tensile strength and flexural strength are shown in Table 4.

[0091] (4) Degradation and recycling of bio-based epoxy resin-carbon fiber composites

[0092] 4.00 g of bio-based epoxy resin-carbon fiber composite material was immersed in 8.00 g of 0.10 mol / L phosphoric acid in a hydrogen peroxide-tetrahydrofuran solution (hydrogen peroxide:tetrahydrofuran = 5:5, m / m), and degraded at 60 °C for 12 h to obtain carbon fiber cloth and degradation solution. The carbon fiber cloth was washed with acetone and dried at 50 °C for 24 h to obtain regenerated carbon fiber cloth. Then, 3.00 g of the regenerated carbon fiber cloth was completely immersed in 2.00 g of thiol-terminated bio-based hyperbranched polymer (BPSPI-6), 20 g of N,N-dimethylformamide, 15 g of tetrahydrofuran, 15 g of 1,4-dioxane, 0.03 g of p-aminophenylacetone, and 0.03 g of... In a mixed solution of 1-hydroxycyclohexylbenzophenone, a thiol-olefin click reaction was carried out by irradiation with 800W ultraviolet light for 40 min to obtain surface-functionalized carbon fiber cloth, namely 5-rTCF. The 5-rTCF was removed and dried at 70℃ for 18 h. 3.00 g of the dried 5-rTCF was placed in a mold, and a mixture of 1.425 g FEP, 0.075 g BPEP-6 and 0.46 g 4,4'-methylenebiscyclohexylamine was uniformly coated on the 5-rTCF in the mold. The mixture was hot-pressed and cured at 80℃ for 3 h at 1 MPa and then at 120℃ for 3 h. After the hot pressing was completed, the mixture was cooled to room temperature and removed to obtain the bio-based epoxy resin-carbon fiber composite material. The mechanical properties of the composite material were tested using a universal testing machine, and its tensile strength is shown in Table 4.

[0093] Example 6: A bio-based epoxy resin-carbon fiber composite material and its preparation method, the steps of which are as follows:

[0094] (1) Synthesis of bio-based hyperbranched epoxy resin containing hexahydrotriazine

[0095] 0.10 mol (14.22 g) of 1,4-cyclohexanedimethylamine and 0.25 mol (24.52 g) of maleic anhydride were mixed thoroughly in 122.60 g of toluene and 122.60 g of N,N-dimethylformamide. Under a nitrogen atmosphere, 0.32 g of p-toluenesulfonic acid and 0.32 g of n-butyl titanate were added, and the mixture was stirred at 135 °C for 12 h. After precipitation in an ice-water bath for 12 h, the solid was filtered to obtain a bio-based bismaleimide monomer. 0.10 mol (13.71 g) of phenylglycine, 0.20 mol (12.00 g) of paraformaldehyde (degree of polymerization 2), and 0.10 mol (14.80 g) of mercaptohexanoic acid were mixed in 164.52 g of acetic acid. The mixture was thoroughly mixed in ethyl acetate and stirred at 60°C for 10 h under a nitrogen atmosphere. The organic solvent was removed by rotary evaporation to obtain the bio-based hexahydrotriazine monomer. In a mixture of 0.03 g p-aminophenylacetone and 0.03 g 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone, 0.01 mol (3.02 g) of bio-based bismaleimide monomer, 0.0105 mol (8.80 g) of bio-based hexahydrotriazine monomer, and 37.40 g of... N,N-Dimethylformamide was reacted with UV light at 600W for 60 min to obtain a thiol-terminated hyperbranched polymer (BPSPI-24); then 0.0114 mol (1.30 g) of allyl glycidyl ether was added and reacted with UV light at 600W for 80 min, followed by rotary evaporation to remove N,N-dimethylformamide, yielding a hexahydrotriazine-containing bio-based hyperbranched epoxy resin (BPEP-24); GPC analysis showed its molecular weight to be approximately 27900 g / mol, and titration yielded an epoxy value of 0.09 mol / 100 g. The results are shown in Tables 1 and 2.

[0096] (2) Performance Study of Bio-based Epoxy Resins

[0097] First, 1.00g of BPEP-24, 2.78g of 4,4'-diaminodiphenylmethane, and 9.00g of FEP were mixed in an oil bath at 125℃ for 2 hours until homogeneous. Then, the mixture was poured into a 10×80mm mold and cured at 60℃ for 1 hour, 80℃ for 3 hours, 130℃ for 1 hour, 170℃ for 2 hours, and 200℃ for 1 hour to obtain the BPEP-24 / FEP composite resin. The mechanical properties of the composite resin were tested using a universal testing machine, and the results are shown in Table 3.

[0098] (3) Preparation of bio-based epoxy resin-carbon fiber composite materials

[0099] 3.00g of carbon fiber cloth (T800) was completely immersed in a mixed solution of 2.50g of thiol-terminated bio-based hyperbranched polymer (BPSPI-24), 30g of acetone, 30g of chloroform, 30g of dichloromethane, and 0.10g of 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone. The solution was then irradiated with 600W ultraviolet light for 60min to induce a thiol-olefin click reaction, yielding surface-functionalized carbon fiber cloth, i.e., 6-TCF. The 6-TCF was removed and dried at 80℃ for 8h. 3.00g of the dried 6-TCF was placed in a mold, and 1.35g of FEP, 0.15g of BPEP-24, and 0.44g of... A mixture of 4,4'-diaminodiphenylmethane was uniformly coated onto 6-TCF in a mold and hot-pressed at 120°C for 3 hours under 10 MPa conditions. After hot pressing, the mixture was cooled to room temperature and removed to obtain a bio-based epoxy resin-carbon fiber composite material. The mechanical properties of the composite material were tested using a universal testing machine, and its tensile strength and flexural strength are shown in Table 4.

[0100] (4) Degradation and recycling of bio-based epoxy resin-carbon fiber composites

[0101] 4.00 g of bio-based epoxy resin-carbon fiber composite material was immersed in 8.00 g of 0.10 mol / L phosphoric acid in a hydrogen peroxide-tetrahydrofuran solution (hydrogen peroxide:tetrahydrofuran = 5:5, m / m), and degraded at 60 °C for 12 h to obtain carbon fiber cloth and degradation solution. The carbon fiber cloth was washed with acetone and dried at 50 °C for 24 h to obtain recycled carbon fiber cloth. Then, 3.00 g of recycled carbon fiber cloth was completely immersed in 2.50 g of thiol-terminated bio-based hyperbranched polymer (BPSPI-24), 30 g of acetone, 30 g of chloroform, 30 g of dichloromethane, and 0.10 g of... A thiol-olefin click reaction was carried out in a mixed solution of 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone under 600W ultraviolet light for 60 min to obtain surface-functionalized carbon fiber cloth, namely 6-rTCF. The 6-rTCF was removed and dried at 80℃ for 8 h. 3.00 g of the dried 6-rTCF was placed in a mold, and a mixture of 1.35 g FEP, 0.15 g BPEP-24 and 0.44 g 4,4'-diaminodiphenylmethane was uniformly coated on the 6-rTCF in the mold. The mixture was hot-pressed and cured at 120℃ for 3 h under 10 MPa. After the hot pressing was completed, the mixture was cooled to room temperature and removed to obtain the bio-based epoxy resin-carbon fiber composite material. The mechanical properties of the composite material were tested using a universal testing machine, and its tensile strength is shown in Table 4.

[0102] Example 7: A bio-based epoxy resin-carbon fiber composite material and its preparation method, the steps of which are as follows:

[0103] (1) Synthesis of bio-based hyperbranched epoxy resin containing hexahydrotriazine

[0104] 0.10 mol (17.02 g) isophorone diamine and 0.25 mol (24.52 g) maleic anhydride were mixed thoroughly in 63.05 g xylene and 63.05 g 1,4-dioxane. 0.39 g p-toluenesulfonic acid was added under a nitrogen atmosphere, and the mixture was stirred at 110 °C for 16 h. After precipitation in an ice-water bath for 12 h, the solid was filtered to obtain a bio-based bismaleimide monomer. 0.10 mol (13.71 g) phenylglycine, 0.10 mol (8.12 g, 37%) formaldehyde aqueous solution, and 0.15 mol (15.90 g) mercaptopropionic acid were mixed thoroughly in 68.55 g dichloromethane and 68.55 g tetrahydrofuran. The mixture was stirred at 25 °C under a nitrogen atmosphere for 16 h. The organic solvent was removed by rotary evaporation to obtain a bio-based hexahydrotriazine monomer. 0.14 g A thiol-terminated hyperbranched polymer (MSPI-4) was obtained by reacting 0.01 mol (3.30 g) of bio-based bismaleimide monomer, 0.02 mol (14.24 g) of bio-based hexahydrotriazine monomer, and 28.48 g of 1,4-dioxane under 1-hydroxycyclohexylphenyl ketone with UV light for 100 min via a click reaction. Then, 0.04 mol (3.93 g) of 1,2-epoxy-5-hexene was added and reacted under UV light for 120 min via a click reaction. The 1,4-dioxane was removed by rotary evaporation, yielding a hexahydrotriazine-containing bio-based hyperbranched epoxy resin (MIEP-4). GPC analysis showed its molecular weight to be approximately 2100 g / mol, and titration yielded an epoxy value of 0.19 mol / 100 g. The results are shown in Tables 1 and 2.

[0105] (2) Performance Study of Bio-based Epoxy Resins

[0106] First, 1.40g of diethylenetriamine, 9.25g of DGEVA and 0.75g of MIEP-4 were mixed in an oil bath at 120℃ for 1 hour until homogeneous. Then, the mixture was poured into a 10×80mm mold and cured at 80℃ for 1 hour, 130℃ for 1 hour and 170℃ for 2 hours to obtain the MIEP-4 / DGEVA composite resin. The mechanical properties of the composite resin were tested using a universal testing machine, and the results are shown in Table 3.

[0107] (3) Preparation of bio-based epoxy resin-carbon fiber composite materials

[0108] 3.00 g of carbon fiber cloth (T300) was completely immersed in a mixed solution of 1.50 g of thiol-terminated bio-based hyperbranched polymer (MSPI-4), 15 g of ethyl acetate, and 0.10 g of p-aminophenylacetone. The solution was then irradiated with 400 W of ultraviolet light for 80 min to induce a thiol-olefin click reaction, yielding surface-functionalized carbon fiber cloth, i.e., 7-TCF. The 7-TCF was removed and dried at 50 °C for 24 h. 3.00 g of the dried 7-TCF was placed in a mold, and a mixture of 1.39 g of DGEVA, 0.11 g of MIEP-4, and 0.21 g of diethylenetriamine was uniformly coated onto the 7-TCF in the mold. The mixture was then hot-pressed at 120 °C for 4 h at 3 MPa. After hot pressing, the mixture was cooled to room temperature and removed to obtain the bio-based epoxy resin-carbon fiber composite material. The mechanical properties of the composite material were tested using a universal testing machine; its tensile strength and flexural strength are shown in Table 4.

[0109] (4) Degradation and recycling of bio-based epoxy resin-carbon fiber composites

[0110] 4.00 g of bio-based epoxy resin-carbon fiber composite material was immersed in 8.00 g of 0.10 mol / L phosphoric acid in a hydrogen peroxide-tetrahydrofuran solution (hydrogen peroxide:tetrahydrofuran = 5:5, m / m). After degradation at 60 °C for 12 h, carbon fiber cloth and degradation solution were obtained. The carbon fiber cloth was washed with acetone and dried at 50 °C for 24 h to obtain regenerated carbon fiber cloth. Then, 3.00 g of the regenerated carbon fiber cloth was completely immersed in a mixed solution of 1.50 g of thiol-terminated bio-based hyperbranched polymer (MSPI-4), 15 g of ethyl acetate and 0.10 g of p-aminophenylacetone. The solution was irradiated with 400 W of ultraviolet light for 80 min to carry out a thiol-olefin click reaction to obtain surface-functionalized carbon fiber cloth, i.e., 7-rTCF. The 7-rTCF was removed and dried at 50 °C for 24 h. 3.00 g of the dried 7-rTCF was placed in a mold, and 1.39 g of DGEVA and 0.11 g of... A mixture of MIEP-4 and 0.21g of diethylenetriamine was uniformly coated onto 7-rTCF in a mold and hot-pressed at 120℃ for 4 hours under 3MPa conditions. After hot pressing, the mixture was cooled to room temperature and removed to obtain a bio-based epoxy resin-carbon fiber composite material. The mechanical properties of the composite material were tested using a universal testing machine, and its tensile strength is shown in Table 4.

[0111] Example 8: A bio-based epoxy resin-carbon fiber composite material and its preparation method, the steps of which are as follows:

[0112] (1) Synthesis of bio-based hyperbranched epoxy resin containing hexahydrotriazine

[0113] 0.10 mol (17.02 g) isophorone diamine and 0.23 mol (22.55 g) maleic anhydride were mixed thoroughly in 120.61 g benzene and 120.61 g N,N-dimethylformamide. 0.26 g n-butyl titanate and 0.26 g tetraisopropyl titanate were added under a nitrogen atmosphere and the mixture was stirred at 160 °C for 8 h. After precipitation in an ice-water bath for 12 h, the solid was filtered to obtain a bio-based bismaleimide monomer. 0.10 mol (13.71 g) phenylglycine, 0.15 mol (12.17 g, 37%) formaldehyde aqueous solution, and 0.15 mol (15.90 g) mercaptopropionic acid were mixed thoroughly in 123.39 g acetone and 123.39 g chloroform. The mixture was stirred at 100 °C for 4 h under a nitrogen atmosphere. The organic solvent was removed by rotary evaporation to obtain a bio-based hexahydrotriazine monomer. 0.12 g A thiol-terminated hyperbranched polymer (MSPI-6) was obtained by clicking reaction of 0.01 mol (3.30 g) of bio-based bismaleimide monomer, 0.013 mol (7.25 g) of bio-based hexahydrotriazine monomer, and 21.75 g of N,N-dimethylformamide under 800 W UV light for 30 min with 1-hydroxycyclohexyl phenyl ketone and 0.12 g p-aminophenylacetone. Then, 0.02 mol (2.56 g) of 2,3-epoxypropyl acrylate was added and the reaction was carried out under 800 W UV light for 60 min. The N,N-dimethylformamide was removed by rotary evaporation, yielding a hexahydrotriazine-containing bio-based hyperbranched epoxy resin (MIEP-6). GPC analysis showed a molecular weight of approximately 4400 g / mol, and titration yielded an epoxy value of 0.13 mol / 100 g. The results are shown in Tables 1 and 2.

[0114] (2) Performance Study of Bio-based Epoxy Resins

[0115] First, 0.50g of MIEP-6, 3.08g of 4,4'-methylenebiscyclohexylamine, and 9.50g of DGEVA were mixed in an oil bath at 120℃ for 1 hour until homogeneous. Then, the mixture was poured into a 10×80mm mold and cured at 50℃ for 1 hour, 130℃ for 1 hour, 170℃ for 2 hours, and 180℃ for 2 hours to obtain the MIEP-6 / DGEVA composite resin. The mechanical properties of the composite resin were tested using a universal testing machine, and the results are shown in Table 3.

[0116] (3) Preparation of bio-based epoxy resin-carbon fiber composite materials

[0117] 3.00g of carbon fiber cloth (T700) was completely immersed in a mixed solution of 2.00g of thiol-terminated bio-based hyperbranched polymer (MSPI-6), 20g of N,N-dimethylformamide, 15g of tetrahydrofuran, 15g of 1,4-dioxane, 0.03g of p-aminophenylacetone, and 0.03g of 1-hydroxycyclohexylacetone. The solution was irradiated with 400W ultraviolet light for 40min to carry out a thiol-olefin click reaction, obtaining surface-functionalized carbon fiber cloth, i.e., 8-TCF. The 8-TCF was then removed and dried at 70℃ for 18h. 3.00g of the dried 8-TCF was placed in a mold, and 1.425g of DGEVA, 0.075g of MIEP-6, and 0.46g of... The mixture of 4,4'-methylene dicyclohexylamine was uniformly coated onto 8-TCF in a mold and cured by hot pressing at 80°C for 3 hours under 1 MPa conditions, followed by hot pressing at 120°C for 3 hours. After hot pressing, the mixture was cooled to room temperature and removed to obtain the bio-based epoxy resin-carbon fiber composite material. The mechanical properties of the composite material were tested using a universal testing machine, and its tensile strength and flexural strength are shown in Table 4.

[0118] (4) Degradation and recycling of bio-based epoxy resin-carbon fiber composites

[0119] 4.00 g of bio-based epoxy resin-carbon fiber composite material was immersed in 8.00 g of 0.10 mol / L phosphoric acid in a hydrogen peroxide-tetrahydrofuran solution (hydrogen peroxide:tetrahydrofuran = 5:5, m / m). After degradation at 60 °C for 12 h, carbon fiber cloth and degradation solution were obtained. The carbon fiber cloth was washed with acetone and dried at 50 °C for 24 h to obtain regenerated carbon fiber cloth. Then, 3.00 g of the regenerated carbon fiber cloth was completely immersed in 2.00 g of thiol-terminated bio-based hyperbranched polymer (MSPI-6), 20 g of N,N-dimethylformamide, 15 g of tetrahydrofuran, 15 g of 1,4-dioxane, 0.03 g of p-aminophenylacetone, and 0.03 g of... In a mixed solution of 1-hydroxycyclohexylbenzophenone, a thiol-olefin click reaction was carried out by irradiation with 400W ultraviolet light for 40 min to obtain surface-functionalized carbon fiber cloth, namely 8-rTCF. The 8-rTCF was removed and dried at 70℃ for 18 h. 3.00 g of the dried 8-rTCF was placed in a mold, and a mixture of 1.425 g DGEVA, 0.075 g MIEP-6 and 0.46 g 4,4'-methylenebiscyclohexylamine was uniformly coated on the 8-rTCF in the mold. The mixture was hot-pressed and cured at 80℃ for 3 h at 1 MPa and then at 120℃ for 3 h. After the hot pressing was completed, the mixture was cooled to room temperature and removed to obtain the bio-based epoxy resin-carbon fiber composite material. The mechanical properties of the composite material were tested using a universal testing machine, and its tensile strength is shown in Table 4.

[0120] Example 9: A bio-based epoxy resin-carbon fiber composite material and its preparation method, the steps of which are as follows:

[0121] (1) Synthesis of bio-based hyperbranched epoxy resin containing hexahydrotriazine

[0122] 0.10 mol (17.02 g) of isophorone diamine and 0.25 mol (24.52 g) of maleic anhydride were mixed thoroughly in 122.60 g of toluene and 122.60 g of N,N-dimethylformamide. 0.32 g of p-toluenesulfonic acid and 0.32 g of n-butyl titanate were added under a nitrogen atmosphere and the mixture was stirred at 135 °C for 12 h. After precipitation in an ice-water bath for 12 h, the solid was filtered to obtain a bio-based bismaleimide monomer. 0.10 mol (13.71 g) phenylglycine, 0.20 mol (12.00 g) paraformaldehyde (degree of polymerization 2), and 0.10 mol (14.80 g) mercaptohexanoic acid were mixed evenly in 164.52 g of ethyl acetate. The mixture was stirred at 60 °C for 10 h under a nitrogen atmosphere. The organic solvent was removed by rotary evaporation to obtain a bio-based hexahydrotriazine monomer. 0.12 g of p-aminophenylacetone and 0.12 g of... A thiol-terminated hyperbranched polymer (MSPI-24) was obtained by reacting 0.01 mol (3.30 g) of bio-based bismaleimide monomer, 0.0105 mol (8.80 g) of bio-based hexahydrotriazine monomer, and 37.40 g of N,N-dimethylformamide under 600 W UV light for 60 min. Then, 0.0114 mol (1.30 g) of allyl glycidyl ether was added and reacted under 600 W UV light for 80 min. The N,N-dimethylformamide was removed by rotary evaporation, yielding a hexahydrotriazine-containing bio-based hyperbranched epoxy resin (MIEP-24). GPC analysis showed a molecular weight of approximately 26800 g / mol, and titration yielded an epoxy value of 0.09 mol / 100 g. The results are shown in Tables 1 and 2.

[0123] (2) Performance Study of Bio-based Epoxy Resins

[0124] First, 1.00g of MIEP-24, 2.93g of 4,4'-diaminodiphenylmethane, and 9.00g of DGEVA were mixed in an oil bath at 125℃ for 2 hours until homogeneous. Then, the mixture was poured into a 10×80mm mold and cured at 60℃ for 1 hour, 80℃ for 3 hours, 130℃ for 1 hour, 170℃ for 2 hours, and 200℃ for 1 hour to obtain the MIEP-24 / DGEVA composite resin. The mechanical properties of the composite resin were tested using a universal testing machine, and the results are shown in Table 3.

[0125] (3) Preparation of bio-based epoxy resin-carbon fiber composite materials

[0126] 3.00g of carbon fiber cloth (T800) was completely immersed in a mixed solution of 2.50g of thiol-terminated bio-based hyperbranched polymer (MSPI-24), 30g of acetone, 30g of chloroform, 30g of dichloromethane, and 0.10g of 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone. The solution was then irradiated with 600W ultraviolet light for 60min to induce a thiol-olefin click reaction, yielding surface-functionalized carbon fiber cloth, i.e., 9-TCF. The 9-TCF was removed and dried at 80℃ for 8h. 3.00g of the dried 9-TCF was placed in a mold, and 1.35g of DGEVA, 0.15g of MIEP-24, and 0.44g of... A mixture of 4,4'-diaminodiphenylmethane was uniformly coated onto 9-TCF in a mold and hot-pressed at 120°C for 3 hours under 10 MPa conditions. After hot pressing, the mixture was cooled to room temperature and removed to obtain a bio-based epoxy resin-carbon fiber composite material. The mechanical properties of the composite material were tested using a universal testing machine, and its tensile strength and flexural strength are shown in Table 4.

[0127] (4) Degradation and recycling of bio-based epoxy resin-carbon fiber composites

[0128] 4.00 g of bio-based epoxy resin-carbon fiber composite material was immersed in 8.00 g of 0.10 mol / L phosphoric acid in a hydrogen peroxide-tetrahydrofuran solution (hydrogen peroxide:tetrahydrofuran = 5:5, m / m), and degraded at 60 °C for 12 h to obtain carbon fiber cloth and degradation solution. The carbon fiber cloth was then washed with acetone and dried at 50 °C for 24 h to obtain recycled carbon fiber cloth. Subsequently, 3.00 g of the recycled carbon fiber cloth was completely immersed in 2.50 g of thiol-terminated bio-based hyperbranched polymer (MSPI-24), 30 g of acetone, 30 g of chloroform, 30 g of dichloromethane, and 0.10 g of... A thiol-olefin click reaction was carried out in a mixed solution of 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone under 600W ultraviolet light for 60 min to obtain surface-functionalized carbon fiber cloth, namely 9-rTCF. The 9-rTCF was removed and dried at 80℃ for 8 h. 3.00 g of the dried 9-rTCF was placed in a mold, and a mixture of 1.35 g DGEVA, 0.15 g MIEP-24 and 0.44 g 4,4'-diaminodiphenylmethane was uniformly coated on the 9-rTCF in the mold. The mixture was hot-pressed and cured at 120℃ for 3 h under 10 MPa. After the hot pressing was completed, the mixture was cooled to room temperature and removed to obtain the bio-based epoxy resin-carbon fiber composite material. The mechanical properties of the composite material were tested using a universal testing machine, and its tensile strength is shown in Table 4.

[0129] Examples 10, 11-I, 11-II, 11-III, and 11-IV describe a bio-based epoxy resin-carbon fiber composite material and its preparation method, the steps of which are as follows:

[0130] Examples 10, 11-I, 11-II, 11-III, and 11-IV follow the same method as Example 9, except for the change in the curing agent and its dosage. Specifically:

[0131] (1) Performance Study of Bio-based Epoxy Resins

[0132] Example 10: The curing agent was diethylenetriamine, and the dosage was 1.58g.

[0133] Example 11-I: The curing agent was 4,4'-methylenebicyclohexylamine, and the dosage was 3.11g.

[0134] Example 11-II: The curing agent was isophorone diamine, and the dosage was 2.47g.

[0135] Example 11-III: The curing agent was 2,2'-diaminodiphenyl sulfide, and the dosage was 3.11g;

[0136] Example 11-IV: The curing agent was 4,4'-diaminodiphenyl sulfide, and the dosage was 3.11g.

[0137] The mechanical properties of the obtained composite resin were tested using a universal testing machine, and the results are shown in Table 3.

[0138] (2) Preparation of bio-based epoxy resin-carbon fiber composite material

[0139] Example 10: The curing agent was diethylenetriamine, and the dosage was 0.24g.

[0140] Example 11-I: The curing agent was 4,4'-methylenebicyclohexylamine, and the dosage was 0.47g.

[0141] Example 11-II: The curing agent was isophorone diamine, and the dosage was 0.37g.

[0142] Example 11-III: The curing agent was 2,2'-diaminodiphenyl sulfide, and the dosage was 0.47g;

[0143] In Examples 11-IV, the curing agent was 4,4'-diaminodiphenyl sulfide, and the dosage was 0.47g.

[0144] The mechanical properties of the obtained composite resin were tested using a universal testing machine, and the results are shown in Table 4.

[0145] (3) Degradation and recycling of bio-based epoxy resin-carbon fiber composites

[0146] The types and amounts of curing agents used in Examples 10, 11-I, 11-II, 11-III, and 11-IV are the same as in step (2).

[0147] The mechanical properties of the obtained composite resin were tested using a universal testing machine, and the results are shown in Table 4.

[0148] Example 12: A bio-based epoxy resin-carbon fiber composite material and its preparation method, the steps of which are as follows:

[0149] (1) Performance Study of Bio-based Epoxy Resins

[0150] First, 1.00g of MIEP-6 (prepared in Example 8), 2.96g of 4,4'-diaminodiphenylmethane, and 9.00g of DGEVA were mixed in an oil bath at 125°C for 2 hours until homogeneous. Then, the mixture was poured into a 10×80mm mold and cured at 60°C for 1 hour, 80°C for 3 hours, 130°C for 1 hour, 170°C for 2 hours, and 200°C for 1 hour to obtain the MIEP-6 / DGEVA-2 composite resin. The mechanical properties of the composite resin were tested using a universal testing machine, and the results are shown in Table 3.

[0151] (2) Preparation of bio-based epoxy resin-carbon fiber composite material

[0152] Example 12 uses the same method as Example 8 for processing carbon fiber, except that T700 is replaced with T800. The surface-functionalized carbon fiber cloth is named 12-TCF. 3.00g of dried 12-TCF is placed in a mold. A mixture of 1.35g DGEVA, 0.15g MIEP-6 and 0.44g 4,4'-diaminodiphenylmethane is evenly coated on the 12-TCF in the mold. The mixture is then hot-pressed and cured at 120℃ for 3 hours under 10MPa. After hot pressing, the mixture is cooled to room temperature and removed to obtain the bio-based epoxy resin-carbon fiber composite material. The mechanical properties of the composite material are tested using a universal testing machine. The tensile strength and flexural strength are shown in Table 4.

[0153] (3) Degradation and recycling of bio-based epoxy resin-carbon fiber composites

[0154] 4.00 g of bio-based epoxy resin-carbon fiber composite material was immersed in 8.00 g of 0.10 mol / L phosphoric acid in a hydrogen peroxide-tetrahydrofuran solution (hydrogen peroxide:tetrahydrofuran = 5:5, m / m), and degraded at 60 °C for 12 h to obtain carbon fiber cloth and degradation solution. The carbon fiber cloth was washed with acetone and dried at 50 °C for 24 h to obtain regenerated carbon fiber cloth. Then, 3.00 g of the regenerated carbon fiber cloth was completely immersed in 2.50 g of thiol-terminated bio-based hyperbranched polymer (MSPI-6, prepared in Example 8), 30 g of acetone, 30 g of chloroform, 30 g of dichloromethane, and 0.10 g of... In a mixed solution of 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone, a thiol-olefin click reaction was carried out under ultraviolet light with a power of 600W for 60 min to obtain surface-functionalized carbon fiber cloth, namely 12-rTCF. The 12-rTCF was removed and dried at 80℃ for 8 h. 3.00 g of the dried 12-rTCF was placed in a mold, and a mixture of 1.35 g DGEVA, 0.15 g MIEP-6 and 0.44 g 4,4'-diaminodiphenylmethane was uniformly coated on the 12-rTCF in the mold. The mixture was hot-pressed and cured at 120℃ for 3 h under 10 MPa. After the hot pressing was completed, the mixture was cooled to room temperature and removed to obtain the bio-based epoxy resin-carbon fiber composite material. The mechanical properties of the composite material were tested using a universal testing machine, and its tensile strength is shown in Table 4.

[0155] Example 13: A bio-based epoxy resin-carbon fiber composite material and its preparation method, the steps of which are as follows:

[0156] (1) Performance Study of Bio-based Epoxy Resins

[0157] First, 1.00g of MIEP-4 (prepared in Example 7), 2.94g of 4,4'-diaminodiphenylmethane, and 9.00g of DGEVA were mixed in an oil bath at 125°C for 2 hours until homogeneous. Then, the mixture was poured into a 10×80mm mold and cured at 60°C for 1 hour, 80°C for 3 hours, 130°C for 1 hour, 170°C for 2 hours, and 200°C for 1 hour to obtain the MIEP-4 / DGEVA-2 composite resin. The mechanical properties of the composite resin were tested using a universal testing machine, and the results are shown in Table 3.

[0158] (2) Preparation of bio-based epoxy resin-carbon fiber composite material

[0159] Example 13 uses the same method as Example 7 for processing carbon fiber, except that T300 is replaced with T800, resulting in a surface-functionalized carbon fiber cloth named 13-TCF. 3.00g of dried 13-TCF is placed in a mold, and a mixture of 1.35g DGEVA, 0.15g MIEP-4, and 0.44g 4,4'-diaminodiphenylmethane is evenly coated onto the 13-TCF in the mold. The mixture is then hot-pressed and cured at 120℃ for 3 hours under 10MPa. After hot pressing, the mixture is cooled to room temperature and removed to obtain a bio-based epoxy resin-carbon fiber composite material. The mechanical properties of the composite material are tested using a universal testing machine, and its tensile strength and flexural strength are shown in Table 4.

[0160] (3) Degradation and recycling of bio-based epoxy resin-carbon fiber composites

[0161] 4.00 g of bio-based epoxy resin-carbon fiber composite material was immersed in 8.00 g of 0.10 mol / L phosphoric acid in a hydrogen peroxide-tetrahydrofuran solution (hydrogen peroxide:tetrahydrofuran = 5:5, m / m), and degraded at 60 °C for 12 h to obtain carbon fiber cloth and degradation solution. The carbon fiber cloth was washed with acetone and dried at 50 °C for 24 h to obtain regenerated carbon fiber cloth. Then, 3.00 g of the regenerated carbon fiber cloth was completely immersed in 2.50 g of thiol-terminated bio-based hyperbranched polymer (MSPI-4, prepared in Example 7), 30 g of acetone, 30 g of chloroform, 30 g of dichloromethane, and 0.10 g of... A thiol-olefin click reaction was carried out in a mixed solution of 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone under 600W ultraviolet light for 60 min to obtain surface-functionalized carbon fiber cloth, namely 13-rTCF. The 13-rTCF was removed and dried at 80℃ for 8 h. 3.00 g of the dried 13-rTCF was placed in a mold, and a mixture of 1.35 g DGEVA, 0.15 g MIEP-4 and 0.44 g 4,4'-diaminodiphenylmethane was uniformly coated on the 13-rTCF in the mold. The mixture was hot-pressed and cured at 120℃ for 3 h under 10 MPa. After the hot pressing was completed, the mixture was cooled to room temperature and removed to obtain the bio-based epoxy resin-carbon fiber composite material. The mechanical properties of the composite material were tested using a universal testing machine, and its tensile strength is shown in Table 4.

[0162] Example 14: A bio-based epoxy resin-carbon fiber composite material and its preparation method, the steps of which are as follows:

[0163] Example 14 follows the same method as Example 3, except that the amount of bio-based epoxy resin and curing agent used is changed. Specifically:

[0164] (1) Performance Study of Bio-based Epoxy Resins

[0165] In Example 14, the basic epoxy resin for bio-based materials was DGEVA, and the amount used was the same as in Example 3. The curing agent and amount used were 2.94 g of 4,4'-diaminodiphenylmethane.

[0166] The mechanical properties of the obtained composite resin were tested using a universal testing machine, and the results are shown in Table 3.

[0167] (2) Preparation of bio-based epoxy resin-carbon fiber composite material

[0168] In Example 14, the bio-based epoxy resin was DGEVA, and its dosage, curing agent and dosage were the same as in Example 3.

[0169] The mechanical properties of the obtained composite resin were tested using a universal testing machine, and the results are shown in Table 4.

[0170] (3) Degradation and recycling of bio-based epoxy resin-carbon fiber composites

[0171] In Example 14, the bio-based epoxy resin was DGEVA, and its dosage, curing agent and dosage were the same as in Example 3.

[0172] The mechanical properties of the obtained composite resin were tested using a universal testing machine, and the results are shown in Table 4.

[0173] Example 15: A bio-based epoxy resin-carbon fiber composite material and its preparation method, the steps of which are as follows:

[0174] Example 15 follows the same method as Example 6, except that the amount of bio-based epoxy resin and curing agent used is changed. Specifically:

[0175] (1) Performance Study of Bio-based Epoxy Resins

[0176] In Example 15, the basic epoxy resin for bio-based materials was DGEVA, and the dosage was the same as in Example 6. The curing agent and dosage were 2.94 g of 4,4'-diaminodiphenylmethane.

[0177] The mechanical properties of the obtained composite resin were tested using a universal testing machine, and the results are shown in Table 3.

[0178] (2) Preparation of bio-based epoxy resin-carbon fiber composite material

[0179] In Example 15, the bio-based epoxy resin was DGEVA, and its dosage, curing agent and dosage were the same as in Example 6.

[0180] The mechanical properties of the obtained composite resin were tested using a universal testing machine, and the results are shown in Table 4.

[0181] (3) Degradation and recycling of bio-based epoxy resin-carbon fiber composites

[0182] In Example 15, the bio-based epoxy resin was DGEVA, and its dosage, curing agent and dosage were the same as in Example 6.

[0183] The mechanical properties of the obtained composite resin were tested using a universal testing machine, and the results are shown in Table 4.

[0184] Comparative Example 1

[0185] (1) Performance Study of Bio-based Epoxy Resins

[0186] First, 2.82g of 4,4'-diaminodiphenylmethane and 10.00g of DGF were mixed in an oil bath at 120℃ for 1 hour until homogeneous. Then, the mixture was poured into a 10×80mm mold and cured at 80℃ for 1 hour, 130℃ for 1 hour, and 170℃ for 2 hours to obtain the DGF resin. The mechanical properties of the resin were tested using a universal testing machine, and the results are shown in Table 3.

[0187] (2) Preparation of bio-based epoxy resin-carbon fiber composite material

[0188] 3.00g of carbon fiber cloth (T800, PCF) was placed in a mold, and a mixture of 1.50g of DGF and 0.42g of 4,4'-diaminodiphenylmethane was evenly coated onto the PCF in the mold. The mixture was then hot-pressed and cured at 120℃ for 4 hours under 3MPa. After the hot pressing was completed, the mixture was cooled to room temperature and removed to obtain the bio-based epoxy resin-carbon fiber composite material. The mechanical properties of the composite material were tested using a universal testing machine, and its tensile strength and flexural strength are shown in Table 4.

[0189] (3) Degradation and recycling of bio-based epoxy resin-carbon fiber composites

[0190] 4.00 g of the composite material was immersed in 20.00 g of 1.00 mol / L phosphoric acid in a hydrogen peroxide-tetrahydrofuran solution (hydrogen peroxide:tetrahydrofuran = 9:1, m / m), and degraded at 80 °C for 6 h to obtain carbon fiber cloth and degradation solution. The carbon fiber cloth was washed with acetone and dried at 70 °C for 10 h to obtain regenerated carbon fiber cloth, i.e., 1-rPCF. Then, 3.00 g of the dried 1-rPCF was placed in a mold, and a mixture of 1.50 g of DGF and 0.42 g of 4,4'-diaminodiphenylmethane was evenly coated on the 1-rPCF in the mold. The mixture was hot-pressed and cured at 120 °C for 4 h under 3 MPa. After hot pressing, the mixture was cooled to room temperature and removed to obtain the bio-based epoxy resin-carbon fiber composite material. The mechanical properties of the composite material were tested using a universal testing machine, and its tensile strength is shown in Table 4.

[0191] Comparative Example 2

[0192] (1) Performance Study of Bio-based Epoxy Resins

[0193] First, 3.00g of 4,4'-diaminodiphenylmethane and 10.00g of FEP were mixed in an oil bath at 120℃ for 1 hour until homogeneous. Then, the mixture was poured into a 10×80mm mold and cured at 80℃ for 1 hour, 130℃ for 1 hour, and 170℃ for 2 hours to obtain the FEP resin. The mechanical properties of the resin were tested using a universal testing machine, and the results are shown in Table 3.

[0194] (2) Preparation of bio-based epoxy resin-carbon fiber composite material

[0195] 3.00g of carbon fiber cloth (T800, PCF) was placed in a mold, and a mixture of 1.50g of FEP and 0.45g of 4,4'-diaminodiphenylmethane was evenly coated onto the PCF in the mold. The mixture was then hot-pressed and cured at 120℃ for 4 hours under 3MPa. After the hot pressing was completed, the mixture was cooled to room temperature and removed to obtain the bio-based epoxy resin-carbon fiber composite material. The mechanical properties of the composite material were tested using a universal testing machine, and its tensile strength and flexural strength are shown in Table 4.

[0196] (3) Degradation and recycling of bio-based epoxy resin-carbon fiber composites

[0197] 4.00 g of the composite material was immersed in a 12.00 g solution of 0.50 mol / L phosphoric acid in hydrogen peroxide and 1,4-dioxane (hydrogen peroxide: 1,4-dioxane = 6:4, m / m). After degradation at 70 °C for 8 h, carbon fiber cloth and degradation solution were obtained. The carbon fiber cloth was washed with acetone and dried at 60 °C for 20 h to obtain regenerated carbon fiber cloth, i.e., 2-rPCF. Then, 3.00 g of the dried 2-rPCF was placed in a mold, and a mixture of 1.50 g of FEP and 0.45 g of 4,4'-diaminodiphenylmethane was evenly coated on the 2-rPCF in the mold. The mixture was hot-pressed and cured at 120 °C for 4 h under 3 MPa. After hot pressing, the mixture was cooled to room temperature and removed to obtain the bio-based epoxy resin-carbon fiber composite material. The mechanical properties of the composite material were tested using a universal testing machine, and its tensile strength is shown in Table 4.

[0198] Comparative Examples 3-I, 3-II, 3-III, 3-IV, 3-V, 3-VI

[0199] Comparative Examples 3-I, 3-II, 3-III, 3-IV, 3-V, and 3-VI differ only in the curing agent and its dosage. Specifically:

[0200] (1) Performance Study of Bio-based Epoxy Resins

[0201] First, 3.24 g of 4,4'-diaminodiphenylmethane and 10.00 g of DGEVA were mixed in an oil bath at 120°C for 1 hour until homogeneous. Then, the mixture was poured into a 10×80 mm mold and cured at 80°C for 1 hour, 130°C for 1 hour, and 170°C for 2 hours to obtain the DGEVA composite resin. The mechanical properties of the resin were tested using a universal testing machine, and the results are shown in Table 3.

[0202] Example 3-I: The curing agent and dosage were 3.24 g of 4,4'-diaminodiphenylmethane;

[0203] Example 3-II: The curing agent and dosage were 1.66 g of diethylenetriamine;

[0204] Example 3-III: The curing agent and dosage were 3.40 g of 4,4'-methylenebicyclohexylamine;

[0205] Example 3-IV: The curing agent and dosage was 2.47 g of isophorone diamine;

[0206] Example 3-V: The curing agent and dosage were 3.40 g of 2,2'-diaminodiphenyl sulfide;

[0207] Example 3-VI: The curing agent and dosage were 3.40 g of 4,4'-diaminodiphenyl sulfide;

[0208] The mechanical properties of the obtained composite resin were tested using a universal testing machine, and the results are shown in Table 3.

[0209] (2) Preparation of bio-based epoxy resin-carbon fiber composite material

[0210] 3.00g of carbon fiber cloth (T800, PCF) was placed in a mold, and a mixture of 1.50g of DGEVA and 0.48g of 4,4'-diaminodiphenylmethane was evenly coated onto the PCF in the mold. The mixture was then hot-pressed and cured at 120℃ for 4 hours under 3MPa. After the hot pressing was completed, the mixture was cooled to room temperature and removed to obtain the bio-based epoxy resin-carbon fiber composite material. The mechanical properties of the composite material were tested using a universal testing machine, and its tensile strength and flexural strength are shown in Table 4.

[0211] Example 3-I: The curing agent and dosage were 0.48 g of 4,4'-diaminodiphenylmethane;

[0212] Example 3-II: The curing agent and dosage were 0.25g of diethylenetriamine;

[0213] Example 3-III: The curing agent and dosage were 0.51g of 4,4'-methylenebicyclohexylamine;

[0214] Example 3-IV: The curing agent and dosage was 0.41g of isophorone diamine;

[0215] Example 3-V: The curing agent and dosage were 0.51 g of 2,2'-diaminodiphenyl sulfide;

[0216] Example 3-VI, the curing agent and dosage is 0.51g of 4,4'-diaminodiphenyl sulfide;

[0217] The mechanical properties of the obtained composite resin were tested using a universal testing machine, and the results are shown in Table 4.

[0218] (3) Degradation and recycling of bio-based epoxy resin-carbon fiber composites

[0219] 4.00 g of the composite material was immersed in 8.00 g of 0.10 mol / L phosphoric acid in a hydrogen peroxide-tetrahydrofuran solution (hydrogen peroxide:tetrahydrofuran = 5:5, m / m), and degraded at 60 °C for 12 h to obtain carbon fiber cloth and degradation solution. The carbon fiber cloth was washed with acetone and dried at 50 °C for 24 h to obtain regenerated carbon fiber cloth, i.e., 3-rPCF. Then, 3.00 g of the dried 3-rPCF was placed in a mold, and a mixture of 1.50 g of DGEVA and 0.48 g of 4,4'-diaminodiphenylmethane was evenly coated on the 3-rPCF in the mold. The mixture was hot-pressed and cured at 120 °C for 4 h under 3 MPa. After the hot pressing was completed, the mixture was cooled to room temperature and removed to obtain the bio-based epoxy resin-carbon fiber composite material. The mechanical properties of the composite material were tested using a universal testing machine, and its tensile strength is shown in Table 4.

[0220] The types and amounts of curing agents in Comparative Examples 3-Ⅰ, 3-Ⅱ, 3-Ⅲ, 3-Ⅳ, 3-V, and 3-VI are the same as in step (2).

[0221] The mechanical properties of the obtained composite resin were tested using a universal testing machine, and the results are shown in Table 4.

[0222] Comparative Example 4

[0223] (1) Performance Study of Bio-based Epoxy Resins

[0224] First, 0.53g of 4,4'-diaminodiphenylmethane and 10.00g of BIEP-24 (prepared in Example 3) were mixed in an oil bath at 120°C for 1 hour until homogeneous. Then, the mixture was poured into a 10×80mm mold and cured at 80°C for 1 hour, 130°C for 1 hour, and 170°C for 2 hours to obtain the BIEP-24 composite resin. The mechanical properties of the resin were tested using a universal testing machine, and the results are shown in Table 3.

[0225] (2) Preparation of bio-based epoxy resin-carbon fiber composite material

[0226] 3.00 g of carbon fiber cloth (T800) was completely immersed in a mixed solution of 1.50 g of thiol-terminated bio-based hyperbranched polymer (BISPI-24, prepared in Example 3), 15 g of ethyl acetate, and 0.03 g of 1-hydroxycyclohexylbenzophenone. The solution was irradiated with 600 W of ultraviolet light for 40 min to carry out a thiol-olefin click reaction, thereby obtaining surface-functionalized carbon fiber cloth, i.e., 3-TCF. The 3-TCF was removed and dried at 50 °C for 24 h. 3.00 g of the dried 3-TCF was placed in a mold, and a mixture of 1.50 g of BISPI-24 and 0.08 g of 4,4'-diaminodiphenylmethane was uniformly coated on the 3-TCF in the mold. The mixture was hot-pressed and cured at 120 °C for 4 h at 3 MPa. After the hot pressing was completed, the mixture was cooled to room temperature and removed to obtain the bio-based epoxy resin-carbon fiber composite material. The mechanical properties of the composite material were tested using a universal testing machine. The tensile strength and flexural strength are shown in Table 4.

[0227] (3) Degradation and recycling of bio-based epoxy resin-carbon fiber composites

[0228] 4.00 g of the composite material was immersed in a 20.00 g solution of 1.00 mol / L phosphoric acid in tetrahydrofuran peroxide (hydrogen peroxide:tetrahydrofuran = 9:1, m / m), and degraded at 80 °C for 6 h to obtain carbon fiber cloth and degradation solution. The carbon fiber cloth was washed with acetone and dried at 70 °C for 10 h to obtain regenerated carbon fiber cloth. Then, 3.00 g of the regenerated carbon fiber cloth was completely immersed in a mixed solution of 1.50 g of thiol-terminated bio-based hyperbranched polymer (BISPI-24), 15 g of ethyl acetate and 0.03 g of 1-hydroxycyclohexyl benzophenone, and irradiated with 600 W of ultraviolet light for 40 min to carry out a thiol-olefin click reaction to obtain surface-functionalized carbon fiber cloth, i.e., 3-rTCF. The 3-rTCF was removed and dried at 50 °C for 24 h. The dried 3.00 g of 3-rTCF was placed in a mold, and 1.50 g of BISPI-24 and 0.08 g of 1-hydroxycyclohexyl benzophenone were added. A mixture of 4,4'-diaminodiphenylmethane was uniformly coated onto 3-rTCF in a mold and hot-pressed at 120°C for 4 hours under 3 MPa conditions. After hot pressing, the mixture was cooled to room temperature and removed to obtain a bio-based epoxy resin-carbon fiber composite material. The mechanical properties of the composite material were tested using a universal testing machine, and its tensile strength is shown in Table 4.

[0229] Comparative Example 5

[0230] Comparative Example 5 was conducted using the same method as Comparative Example 4, except that the hexahydrotriazine-containing bio-based hyperbranched epoxy resin and the thiol-terminated bio-based hyperbranched polymer were replaced. In Comparative Example 5, the bio-based hyperbranched epoxy resin and the thiol-terminated bio-based hyperbranched polymer were BPEP-24 and BPSPI-24 prepared in Example 6.

[0231] The mechanical properties of the resin were tested using a universal testing machine, and the results are shown in Table 3. The tensile strength and flexural strength of the bio-based epoxy resin-carbon fiber composite were also tested using a universal testing machine, and are shown in Table 4.

[0232] Comparative Example 6

[0233] Comparative Example 6 was conducted using the same method as Comparative Example 4, except that the hexahydrotriazine-containing bio-based hyperbranched epoxy resin and the thiol-terminated bio-based hyperbranched polymer were replaced. In Comparative Example 6, the bio-based hyperbranched epoxy resin and the thiol-terminated bio-based hyperbranched polymer were MIEP-24 and MSPI-24 prepared in Example 9.

[0234] The mechanical properties of the resin were tested using a universal testing machine, and the results are shown in Table 3. The tensile strength and flexural strength of the bio-based epoxy resin-carbon fiber composite were also tested using a universal testing machine, and are shown in Table 4.

[0235] Table 1. Number average molecular weight of the bio-based terminal thiol hyperbranched polymers prepared in Examples 1-9

[0236] Examples Product Name Number average molecular weight (g / mol) of end-mercapto hyperbranched polymer Example 1 BISPI-4 1700 Example 2 BISPI-6 3800 Example 3 BISPI-24 23300 Example 4 BPSPI-4 1600 Example 5 BPSPI-6 3700 Example 6 BPSPI-24 25200 Example 7 MSPI-4 1700 Example 8 MSPI-6 3800 Example 9 MSPI-24 24100

[0237] Table 2. Number-average molecular weight and epoxy value of the bio-based hyperbranched epoxy resins prepared in Examples 1-9

[0238] Examples Product Name Number average molecular weight (g / mol) of hyperbranched epoxy resin Epoxy value (mol / 100g) Example 1 BIEP-4 2100 0.19 Example 2 BIEP-6 4600 0.13 Example 3 BIEP-24 26000 0.09 Example 4 BPEP-4 2100 0.19 Example 5 BPEP-6 4400 0.13 Example 6 BPEP-24 27900 0.09 Example 7 MIEP-4 2100 0.19 Example 8 MIEP-6 4400 0.13 Example 9 MIEP-24 26800 0.09

[0239] Table 3 Performance test results of the bio-based epoxy resin composite resins prepared in Examples 1-15

[0240]

[0241]

[0242] Table 4 Performance test results of the bio-based epoxy resin / carbon fiber composites prepared in Examples 1-15

[0243]

[0244]

[0245] 1) The test results in Table 1 show that:

[0246] The number-average molecular weight of the terminal thiol hyperbranched polymers obtained in Examples 1-3, 4-6 and 7-9 of this invention gradually increases with the increase of the number of terminal thiol groups; when the number of terminal thiol groups is 24, the number-average molecular weight reaches its maximum value.

[0247] 2) The test results in Table 2 show that:

[0248] The number-average molecular weight of the hexahydrotriazine-containing bio-based hyperbranched epoxy resins obtained in Examples 1-3, 4-6 and 7-9 of this invention gradually increases with the increase of the number of terminal epoxy groups; among them, the number-average molecular weight reaches the maximum when the number of terminal epoxy groups is 24.

[0249] The hexahydrotriazine-containing bio-based hyperbranched epoxy resins obtained in Examples 1-3 and 7-9 of this invention showed a gradual decrease in epoxy value as the number of terminal epoxy groups increased; the epoxy value was highest when the number of terminal epoxy groups was 4, and the epoxy value was 0.19 mol / 100g.

[0250] 3) The test results in Tables 3 and 4 show that:

[0251] The bio-based epoxy resin composite resins obtained in Examples 1-3, 4-6, and 7-9 of this invention showed that different numbers of terminal epoxy groups, different curing agents, and different mass fractions of bio-based hyperbranched epoxy resin resulted in different tensile and flexural strengths of the composite resins. Specifically, when the number of terminal epoxy groups was 24, the curing agent was 4,4'-diaminodiphenylmethane, and the mass fraction of bio-based hyperbranched epoxy resin was 10%, the tensile and flexural strengths of the bio-based epoxy resin composite resin reached their maximum values. Furthermore, comparing different bio-based epoxy resin-carbon fiber composite materials, it was found that different types of carbon fiber cloth, different bio-based epoxy resins, different mass ratios of carbon fiber to end-thiol hyperbranched polymer, and different mass fractions of bio-based hyperbranched epoxy resin resulted in different tensile and flexural strengths of the composite materials. Specifically, when the carbon fiber cloth was T800, the mass ratio of carbon fiber to end-thiol hyperbranched polymer was 3.0:2.5, and the mass fraction of bio-based hyperbranched epoxy resin was 10%, the tensile and flexural strengths of the composite material reached their maximum values.

[0252] In Examples 1, 4, and 7 of this invention, the different structures of the bio-based diamines resulted in different bio-based epoxy resin composites, leading to variations in their tensile and flexural strengths. The tensile and flexural strengths reached their maximum values ​​when the bio-based diamine was isophorone diamine. This is because the bio-based diamine in Example 1 contains a five-membered ring, while the bio-based diamines in Examples 4 and 7 contain a six-membered ring. Therefore, the tensile and flexural strengths of the bio-based epoxy resin composite in Example 1 are lower than those in Examples 4 and 7. Furthermore, the bio-based diamine in Example 7 contains a shorter linear structure than that in Example 4, resulting in higher tensile and flexural strengths than those in Example 4. The same reasoning also affects the differences in the tensile and flexural strengths of the bio-based epoxy resin-carbon fiber composite.

[0253] In Examples 9, 10, 11-I, 11-II, 11-III, and 11-IV of this invention, using the same bio-based epoxy resin, the same number of terminal epoxy groups, the same carbon fiber cloth, the same mass ratio of carbon fiber to end-thiol hyperbranched polymer, and the same mass fraction of bio-based hyperbranched epoxy resin, different curing agents resulted in different tensile and flexural strengths of the bio-based epoxy resin composite resin and the bio-based epoxy resin-carbon fiber composite resin. When the curing agent was 4,4'-diaminodiphenylmethane, the tensile and flexural strengths of the bio-based epoxy resin composite resin reached their maximum values ​​of 97±4 MPa and 167±4 MPa, respectively, representing increases of 40.58% and 40.34% compared to Comparative Example 3-I. The tensile and flexural strengths of the bio-based epoxy resin-carbon fiber composite resin also reached their maximum values ​​of 919±14 MPa and 946±13 MPa, respectively, representing increases of 27.29% and 30.48% compared to Comparative Example 3-I. Comparing Examples 9, 10, 11-I, 11-II, 11-III, and 11-IV with Comparative Examples 3-I, 3-II, 3-III, 3-IV, 3-V, and 3-VI, it can be seen that the bio-based hyperbranched epoxy resin MIEP-24 significantly enhances and toughens the bio-based linear epoxy resin DGEVA when using different curing agents. Similarly, comparing Examples 7 and 8 with Comparative Examples 3-II and 3-III, it can be seen that the bio-based hyperbranched epoxy resins MIEP-4 and MIEP-6 significantly enhance and toughen the bio-based linear epoxy resin DGEVA when using different curing agents.

[0254] In Examples 9 and 12-13 of this invention, the same curing agent, the same bio-based epoxy resin, the same carbon fiber cloth, the same mass ratio of carbon fiber to terminal thiol hyperbranched polymer, and the same mass fraction of bio-based hyperbranched epoxy resin were used. However, the different number of terminal epoxy groups resulted in different tensile and flexural strengths in the bio-based epoxy resin composite resin and the bio-based epoxy resin-carbon fiber composite resin. When the number of terminal epoxy groups was 24, the tensile and flexural strengths of the composite resin reached their maximum values, at 97±4 MPa and 167±4 MPa, respectively; the tensile and flexural strengths of the bio-based epoxy resin-carbon fiber composite resin also reached their maximum values, at 919±14 MPa and 946±13 MPa, respectively. Compared to Comparative Example 6, the composite resins and composite materials prepared in Examples 9 and 14-15 also showed significant improvements in tensile and flexural strength.

[0255] In Examples 9 and 14-15 of this invention, the same curing agent, the same bio-based basic epoxy resin, the same carbon fiber cloth, the same mass ratio of carbon fiber to end-thiol hyperbranched polymer, the same number of end epoxy groups, and the same mass fraction of bio-based hyperbranched epoxy resin are used. Different bio-based hyperbranched epoxy resins result in different tensile and flexural strengths of bio-based epoxy resin composite resin and bio-based epoxy resin-carbon fiber composite resin. The main reason for this is the difference in the diamine used to synthesize the hyperbranched epoxy resin. When the diamine is isophorone diamine, the tensile and flexural strengths of both the bio-based epoxy resin composite resin and the bio-based epoxy resin-carbon fiber composite resin reach their maximum values.

[0256] Compared with Comparative Examples 6, 4, and 5, the bio-based epoxy resin composite resin and bio-based epoxy resin-carbon fiber composite material prepared in Examples 9, 14, and 15 showed significant improvements in tensile strength and flexural strength.

[0257] In Examples 14, 3, 15, and 6 of this invention, only the bio-based epoxy resin is different. The tensile strength and flexural strength properties of the prepared bio-based epoxy resin composite resin and bio-based epoxy resin-carbon fiber composite material are comparable, with DGEVA being slightly better.

[0258] The acidic hydrogen peroxide solution degradation system provided by this invention enables the degradation, recycling, and reuse of bio-based epoxy resin / carbon fiber composite materials. A comparison of the tensile strength of the composite material prepared from the recycled carbon fiber fabric with the tensile strength of the original composite material shows that the tensile strength of the recycled carbon fiber fabric does not decrease significantly, exhibiting a high retention rate of over 88%.

[0259] In summary, the combination of hexahydrotriazine-containing bio-based hyperbranched epoxy resin and bio-based linear epoxy resin of the present invention can significantly improve the tensile strength and flexural strength of bio-based epoxy resin-carbon fiber composite materials, achieving the goal of using low-grade carbon fiber to achieve the strength of high-grade carbon fiber, while realizing the recycling of carbon fiber, and the tensile strength of recycled carbon fiber fabric composite materials does not decrease significantly.

[0260] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A hexahydro-mutisiloxane bio-based hyperbranched epoxy resin, characterized in that, The structural formula is shown as general formula (1): General formula (1) The structure of R is as follows: n is a natural number of 1 to 5, and R is connected to -CO- and -CH20-. The structure of R is as follows: The structure of R is as follows: The structure of R is as follows: The structure of R is as follows: The structure of R is as follows: The structure of R is as follows: The number average molecular weight of the bio-based hyperbranched epoxy resin containing hexahydro-s-triazine is 2000-28000 g / mol, and the epoxy value is 0.09-0.19 mol / 100g.

2. The process for the preparation of a hexahydro-s-triazine bio-based hyperbranched epoxy resin according to claim 1, characterized in that, The method comprises the following steps: The bio-based diamine and maleic anhydride are mixed uniformly in a water-carrying agent, a catalyst is added under a nitrogen atmosphere, and the mixture is stirred at 110-160 DEG C for 8-16 h, and then precipitated in an ice-water bath, and the solid is filtered to obtain a bio-based bismaleimide monomer; the phenylglycinol, aldehyde compound and mercaptoalkyl acid are mixed uniformly in an organic solvent, stirred at 25-100 DEG C for 4-16 h under a nitrogen atmosphere, and the solvent is removed by rotary evaporation to obtain a bio-based hexahydro-s-triazine monomer; the bio-based bismaleimide monomer, bio-based hexahydro-s-triazine monomer and organic solvent are subjected to a click reaction under a photoinitiator by using ultraviolet light with a power of 400W-800W for 30-100 min to obtain a thiol-terminated hyperbranched polymer; then an alkenyl epoxy compound is added and subjected to a click reaction by using ultraviolet light with a power of 400W-800W for 60-120 min, and the organic solvent is removed by rotary evaporation to obtain the bio-based hyperbranched epoxy resin containing hexahydro-s-triazine, with a number average molecular weight of 2000-28000 g / mol and an epoxy value of 0.09-0.19 mol / 100g; The molar ratio of the bio-based diamine and maleic anhydride is 1:(2.10-2.50); the molar ratio of the phenylglycinol, aldehyde compound and mercaptoalkyl acid is 1:(1-2):(1-2); the molar ratio of the bio-based bismaleimide and bio-based hexahydro-s-triazine is 1:(1.05-2); and the molar ratio of the bio-based hexahydro-s-triazine monomer and alkenyl epoxy compound is 1:(1.09-2).

3. The preparation method according to claim 2, characterized in that, The bio-based diamine is one or more of 2,5-furandimethylamine, 1,4-cyclohexanedimethylamine, and isophorone diamine; the mercaptoalkyl acid is n is a natural number of 1 to 5; the aldehyde compound is one or more of an aqueous formaldehyde solution, a trimeric formaldehyde, and a polymeric formaldehyde; and the alkenyl epoxy compound is one or more of 1,2-epoxy-5-hexene, allyl glycidyl ether, and 2,3-epoxypropyl acrylate.

4. The production method according to claim 2, characterized by, The water-carrying agent is one or more of toluene, benzene, 1,4-dioxane, xylene and N,N-dimethylformamide, and the mass of the water-carrying agent added is 5-15 times the mass of the maleic anhydride; the catalyst is one or more of n-butyl titanate, tetraisopropyl titanate or p-toluenesulfonic acid, and the mass of the catalyst added is 1.5-3.0% of the mass of the maleic anhydride; the organic solvent for synthesizing the bio-based hexahydro-sym-triazine monomer is one or more of acetone, chloroform, ethyl acetate, dichloromethane, tetrahydrofuran, toluene, xylene, 1,4-dioxane, and the mass of the organic solvent added is 5-18 times the mass of the benzoguanamine; the photoinitiator is one or more of p-aminopropiophenone, 1-hydroxycyclohexyl phenyl ketone, 4-dimethylaminopyridine, benzophenone, 2,2-dimethoxy-2-phenylacetophenone and 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone, and the mass of the photoinitiator added is 1.0-3.5% of the mass of the bio-based hexahydro-sym-triazine; the organic solvent for synthesizing the end-mercapto hyperbranched polymer is one or more of dichloromethane, tetrahydrofuran, water, N,N-dimethylformamide, xylene, toluene and 1,4-dioxane, and the mass of the organic solvent added is 2-5 times the mass of the bio-based hexahydro-sym-triazine monomer.

5. A bio-based epoxy resin composite material, characterized by, The composite material comprises the bio-based hyperbranched epoxy resin containing hexahydro-sym-triazine according to claim 1 or the bio-based hyperbranched epoxy resin containing hexahydro-sym-triazine prepared by the method according to any one of claims 2-4 and a bio-based linear epoxy resin, and the epoxy value of the bio-based linear epoxy resin is 0.10-0.90 mol / 100g.

6. The bio-based epoxy resin composite material according to claim 5, characterized in that, The bio-based hyperbranched epoxy resin containing hexahydro-sym-triazine, the bio-based linear epoxy resin and a curing agent are uniformly mixed, and then poured into a mold for thermal curing to obtain the composite material; the curing agent is one or more of 4,4'-methylenebis(cyclohexylamine), 4,4'-diaminodiphenylmethane, diethylenetriamine, isophorone diamine, 2,2'-diaminodi-phenyl sulfide and 4,4'-diaminodiphenyl sulfide.

7. The bio-based epoxy resin composite material according to claim 6, characterized in that, The mass ratio of the bio-based hyperbranched epoxy resin containing hexahydro-sym-triazine to the bio-based linear epoxy resin is (0.5-1):(9-9.5).

8. A bio-based epoxy resin / carbon fiber composite material, characterized by, The composite material is prepared by blending and filling the bio-based hyperbranched epoxy resin containing hexahydro-sym-triazine according to claim 1 or the bio-based hyperbranched epoxy resin containing hexahydro-sym-triazine prepared by the method according to any one of claims 2-4 and a bio-based linear epoxy resin in a carbon fiber cloth, and then laminating and curing; before curing, the carbon fiber cloth is modified by thiol-olefin click reaction with the end-mercapto hyperbranched polymer prepared by the method according to any one of claims 2-4 to obtain a surface-functionalized carbon fiber cloth.

9. The bio-based epoxy resin / carbon fiber composite material according to claim 8, characterized in that, The preparation method comprises the following steps: immersing the carbon fiber cloth into a mixed solution of the terminal mercapto hyperbranched polymer prepared by the method of any one of claims 2-4, an organic solvent and a photoinitiator, and performing a thiol-alkene click reaction under the action of the photoinitiator by using ultraviolet light with a power of 400 W-800 W for 40-80 min; after the reaction is completed, the carbon fiber cloth is taken out and dried at 50-80 ℃ for 8-24 h, so that the surface functionalized carbon fiber cloth is obtained; the surface functionalized carbon fiber cloth is placed in a mold, and the hexahydro-s-triazine bio-based hyperbranched epoxy resin of claim 1 or the mixture of the hexahydro-s-triazine bio-based hyperbranched epoxy resin prepared by the method of any one of claims 2-4, the bio-based linear epoxy resin and the curing agent is uniformly applied on the surface functionalized carbon fiber cloth, and the hot-pressing curing is performed at 1-10 MPa and 80-180 ℃ for 3-6 h, and after cooling to room temperature, the bio-based epoxy resin / carbon fiber composite material is obtained.

10. The bio-based epoxy resin / carbon fiber composite material according to claim 9, characterized in that, The mass ratio of the carbon fiber cloth to the terminal mercapto hyperbranched polymer is 1:(0.50-0.83); the mass ratio of the surface functionalized carbon fiber cloth, the hexahydro-s-triazine bio-based hyperbranched epoxy resin and the bio-based linear epoxy resin is (0.90-0.95):(0.01-0.05):(0.45-0.50).

11. The bio-based epoxy resin / carbon fiber composite of claim 9, wherein, The photoinitiator is one or more of p-aminopropiophenone, 4-dimethylaminopyridine, benzophenone, 1-hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-2-phenylacetophenone and 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone, and the mass of the added photoinitiator is 1.0-3.5% of the mass of the carbon fiber cloth; the organic solvent is one or more of tetrahydrofuran, 1,4-dioxane, ethyl acetate, anhydrous ethanol, methanol, dimethyl sulfoxide, toluene, xylene, acetone, chloroform, N,N-dimethylformamide and dichloromethane, and the mass of the organic solvent is 5-30 times of the mass of the carbon fiber cloth; and the curing agent is one or more of 4,4'-methylenebis(cyclohexylamine), 4,4'-diaminodiphenylmethane, diethylenetriamine, isophorone diamine, 2,2'-diaminodi-phenyl sulfide and 4,4'-diaminodiphenyl sulfide.

12. A method for degradation and recycling of a bio-based epoxy resin / carbon fiber composite material, characterized by, The method comprises the following steps: immersing the bio-based epoxy resin / carbon fiber composite material of any one of claims 8-11 in an acidic hydrogen peroxide solution, and after degradation at 60-80 ℃ for 6-12 h, the carbon fiber cloth and the degradation liquid are obtained; the carbon fiber cloth is washed with acetone and dried at 50-70 ℃ for 10-24 h, so that the regenerated carbon fiber cloth is obtained.

13. The degradation recycling method of claim 12, wherein, The acid hydrogen peroxide solution is a hydrogen peroxide solution of phosphoric acid or hydrochloric acid, the concentration of the acid is 0.10-1.00 mol / L, the solvent in the acid hydrogen peroxide solution is one or more of tetrahydrofuran, 1,4-dioxane, acetone, water and N,N-dimethylformamide, and the mass percentage of hydrogen peroxide in the acid hydrogen peroxide solution is 50%-90%; the mass ratio of the bio-based epoxy resin / carbon fiber composite material to the acid hydrogen peroxide solution is 1:(2-5).

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