Heat-resistant carbon fiber and preparation method thereof

Abstract

The invention relates to the technical field of carbon fiber materials, and discloses heat-resistant carbon fiber and a preparation method thereof.The heat-resistant carbon fiber comprises, by weight, 100 parts of polyurethane resin and 1-6 parts of modified carbon fiber; the surface of the modified carbon fiber is grafted with a hyperbranched polymer containing a carbamate structural unit, so that the compatibility between the carbon fiber and polyurethane is improved, the dispersity of the carbon fiber in the polyurethane is improved, and the carbon fiber and the hyperbranched polymer play a synergistic enhancement role; the tensile strength and the elongation at break of the polyurethane-based heat-resistant carbon fiber are improved. The modified carbon fiber grafted hyperbranched polymer contains a heat-resistant triazine functional group, so that the heat resistance, the limit oxygen index and the flame retardant property of polyurethane are improved.

Description

Technical Field

[0001] The invention relates to the technical field of carbon fiber materials, and in particular to a heat-resistant carbon fiber and a preparation method thereof. Background Art

[0002] Carbon fiber is a high-strength and high-modulus fiber widely used in polymer materials such as rubber and plastics. It can significantly improve the heat resistance, mechanical strength, flame retardancy and other properties of the material. The difficulty of organic surface modification of carbon fiber and improving the compatibility between carbon fiber and materials is a research point. Patent CN105199368B discloses a modified carbon fiber reinforced thermoplastic polyurethane composite material and a preparation method thereof. The carbon fiber is subjected to electrochemical grafting modification treatment and reacted with diphenylmethane diisocyanate. The modified carbon fiber obtained can improve the strength and rigidity of the polyurethane material, but the modified carbon fiber does not improve the heat resistance, flame retardancy and other properties of the polyurethane material.

[0003] Using hyperbranched polymers to blend and modify polyurethane is an effective method to improve its mechanical properties. Patent CN109468843B discloses a method of grafting hydroxyl-terminated hyperbranched polymers on the surface of carbon fibers, which significantly improves the wettability and adhesion between carbon fibers and resins, improves the interface properties of composite materials, and further improves the mechanical properties and thermal stability of composite materials. However, the hydroxyl-terminated hyperbranched polymer grafted carbon fibers in this patent do not improve the flame retardant properties of resin materials. Summary of the invention

[0004] The technical problem solved by the present invention is to provide a heat-resistant carbon fiber and a preparation method thereof, thereby solving the problem of poor heat resistance and mechanical strength of polyurethane.

[0005] The technical solution provided by the present invention is: a heat-resistant carbon fiber, comprising 100 parts by weight of polyurethane resin and 1-6 parts by weight of modified carbon fiber.

[0006] The preparation method of modified carbon fiber is:

[0007] (1) Add oxidized carbon fiber, hydroxyethyl acrylate-TD I semi-addition product, and dibutyltin dilaurate to toluene, heat to 100-110°C, stir and react for 8-12 hours, filter, wash with ethanol, and dry to obtain vinyl carbon fiber. The reaction formula is:

[0008]

[0009] (2) Add vinyl carbon fiber, vinyl triazine monomer, and ethylene glycol bis(thioglycolate) to N,N-dimethylacetamide, introduce nitrogen, add triethylamine, stir and react at room temperature for 6-12 hours, pour the solution into ethanol, filter, wash with ethanol, and dry to obtain modified carbon fiber. The reaction formula is:

[0010]

[0011] Preferably, in (1), the mass of hydroxyethyl acrylate-TD I semi-addition product and dibutyltin dilaurate is 50-200% and 6-28% of the mass of the oxidized carbon fiber.

[0012] Preferably, in (2), the masses of vinyl triazine monomer, ethylene glycol bis(thioglycolate) and triethylamine are 220-650%, 65-200% and 3-10% of the mass of the vinyl carbon fiber, respectively.

[0013] Preferably, the preparation method of the vinyl triazine monomer is: add hydroxyethyl acrylate-TD I semi-addition product, 2,4,6-tri(ethanolamino)-triazine, dibutyltin dilaurate to toluene, 1,4-dioxane, ethyl acetate or tetrahydrofuran solvent, heat to 60-100°C, stir to react for 4-8h, distill under reduced pressure, and recrystallize the product with ethyl acetate to obtain the vinyl triazine monomer. The reaction formula is:

[0014]

[0015] Preferably, the semi-addition product of hydroxyethyl acrylate-TDI and the patent of dibutyltin dilaurate are 340-400% and (2.7-3.6)% of the mass of 2,4,6-tri(ethanolamino)-s-triazine respectively.

[0016] Preferably, the preparation method of heat-resistant carbon fiber is: adding polyurethane resin and modified carbon fiber to a torque rheometer, kneading at 145-160°C for 10-20 minutes, then hot pressing the material at 145-160°C for 5-8 minutes at 10-15MPa in a hot press, and then cold pressing at room temperature for 5-10 minutes at 10-15MPa to obtain heat-resistant carbon fiber.

[0017] The technical effect of the present invention is that the present invention utilizes the isocyanate group of the hydroxyethyl acrylate-TDI semi-addition product to react with the hydroxyl group on the surface of the oxidized carbon fiber, thereby introducing olefin groups on the surface of the carbon fiber to obtain vinyl carbon fiber.

[0018] The present invention uses the olefin group of vinyl carbon fiber as a polymerization site, vinyl triazine monomer, ethylene glycol bis(thioglycolate) as a polymerization monomer, and triethylamine as a catalyst to cause a thiol-olefin grafting polymerization reaction on the surface of the carbon fiber to obtain a hyperbranched polymer grafted modified carbon fiber, which is then blended and compounded with a polyurethane resin to obtain a polyurethane-based heat-resistant carbon fiber.

[0019] The present invention adds modified carbon fiber to polyurethane, and a hyperbranched polymer containing carbamate structural units is grafted on the surface of the carbon fiber, which has good interface compatibility with the polyurethane containing carbamate groups, thereby improving the compatibility between the carbon fiber and the polyurethane, improving the dispersibility of the carbon fiber in the polyurethane, making the carbon fiber have a good reinforcement effect, playing a synergistic reinforcement role with the hyperbranched polymer, and improving the tensile strength and elongation at break of the polyurethane-based heat-resistant carbon fiber.

[0020] The hyperbranched polymer grafted with the modified carbon fiber of the present invention contains a heat-resistant triazine functional group, which is beneficial to improving the heat resistance of polyurethane. After high-temperature heat treatment, the polyurethane-based heat-resistant carbon fiber still maintains good tensile strength and elongation at break. In addition, the nitrogen-rich triazine functional group contained in the hyperbranched polymer can generate a large amount of non-combustible gases such as nitrogen when burned, which is beneficial to dilute oxygen and take away the heat of the combustion system, thereby improving the limiting oxygen index of the polyurethane-based heat-resistant carbon fiber and improving the flame retardant performance. DETAILED DESCRIPTION

[0021] The CAS registration number of 2,4,6-tri(ethanolamino)-s-triazine is 4403-07-0. The CAS registration number of ethylene glycol bis(thioglycolate) is 123-81-9. The CAS registration number of trimethylolpropane triacrylate is 15625-89-5. The polyurethane resin brand is BASF C85A10.

[0022] Preparation method of oxidized carbon fiber: add 6g of carbon fiber (average length 3mm) to 30mL of 98% concentrated sulfuric acid and 90mL of 70% concentrated nitric acid, heat to 80°C, oxidize for 4h, filter, wash with water, and dry to obtain oxidized carbon fiber.

[0023] The preparation method of the hydroxyethyl acrylate-TD I semi-addition product is as follows: 100 mmol of toluene-2,4-diisocyanate is added to a flask under an ice bath, 100 mmol of hydroxyethyl acrylate is added dropwise, and the molar amount of NCO is determined by the di-n-butylamine method during the reaction. When the molar amount of NCO is 50 mmol, the reaction is stopped, and the mixture is cooled to obtain the hydroxyethyl acrylate-TD I semi-addition product, the structural formula of which is as follows:

[0024]

[0025] Example 1

[0026] (1) Add 0.8 g of hydroxyethyl acrylate-TD I semi-addition product, 0.2 g of 2,4,6-tri(ethanolamino)-s-triazine, and 5.4 mg of dibutyltin dilaurate to tetrahydrofuran solvent, heat to 60° C., stir to react for 8 h, and distill under reduced pressure. The product is recrystallized from ethyl acetate to obtain a vinyl triazine monomer.

[0027] (2) Add 0.5 g of oxidized carbon fiber, 0.75 g of hydroxyethyl acrylate-TDI semi-addition product, and 0.1 g of dibutyltin dilaurate to 20 mL of toluene, heat to 110° C., stir to react for 8 h, filter, wash with ethanol, and dry to obtain vinyl carbon fiber.

[0028] (3) Add 1 g of vinyl carbon fiber, 5.2 g of vinyl triazine monomer, and 1.58 g of ethylene glycol bis(thioglycolate) to 70 mL of N,N-dimethylacetamide, introduce nitrogen, add 0.07 g of triethylamine, and stir the reaction at room temperature for 12 h. Pour the solution into ethanol, filter, wash with ethanol, and dry to obtain modified carbon fiber.

[0029] (4) Add 1 kg of polyurethane resin and 10 g of modified carbon fiber into a torque rheometer, knead at 145 ° C for 20 min, then hot press the material at 145 ° C for 8 min at 10 MPa in a hot press, and then cold press at room temperature for 10 min at 10 MPa to obtain heat-resistant carbon fiber.

[0030] Example 2

[0031] (1) Add 0.68 g of hydroxyethyl acrylate-TDI semi-addition product, 0.2 g of 2,4,6-tris(ethanolamino)-triazine, and 5.4 mg of dibutyltin dilaurate to 1,4-dioxane, heat to 100°C, stir and react for 8 hours, distill under reduced pressure, and recrystallize the product with ethyl acetate to obtain a vinyl triazine monomer.

[0032] (2) Add 0.5 g of oxidized carbon fiber, 1 g of hydroxyethyl acrylate-TDI semi-addition product, and 0.14 g of dibutyltin dilaurate to 30 mL of toluene, heat to 100° C., stir to react for 12 h, filter, wash with ethanol, and dry to obtain vinyl carbon fiber.

[0033] (3) Add 1 g of vinyl carbon fiber, 2.2 g of vinyl triazine monomer, and 0.65 g of ethylene glycol bis(thioglycolate) to 60 mL of N,N-dimethylacetamide, introduce nitrogen, add 0.03 g of triethylamine, and stir the reaction at room temperature for 12 h. Pour the solution into ethanol, filter, wash with ethanol, and dry to obtain modified carbon fiber.

[0034] (4) Add 1 kg of polyurethane resin and 25 g of modified carbon fiber into a torque rheometer, knead at 160°C for 10 min, then hot press the material at 160°C for 5 min at 10 MPa in a hot press, and then cold press at room temperature for 10 min at 10 MPa to obtain heat-resistant carbon fiber.

[0035] Example 3

[0036] (1) Add 0.72 g of hydroxyethyl acrylate-TDI semi-addition product, 0.2 g of 2,4,6-tris(ethanolamino)-triazine, and 7.2 mg of dibutyltin dilaurate to toluene, heat to 100°C, stir and react for 5 h, distill under reduced pressure, and recrystallize the product with ethyl acetate to obtain a vinyl triazine monomer.

[0037] (2) Add 0.5 g of oxidized carbon fiber, 0.25 g of hydroxyethyl acrylate-TDI semi-addition product, and 0.03 g of dibutyltin dilaurate to 20 mL of toluene, heat to 100° C., stir and react for 10 h, filter, wash with ethanol, and dry to obtain vinyl carbon fiber.

[0038] (3) Add 1 g of vinyl carbon fiber, 6.5 g of vinyl triazine monomer, and 2 g of ethylene glycol bis(thioglycolate) to 80 mL of N,N-dimethylacetamide, introduce nitrogen, add 0.1 g of triethylamine, stir and react at room temperature for 12 h, pour the solution into ethanol, filter, wash with ethanol, and dry to obtain modified carbon fiber.

[0039] (4) Add 1 kg of polyurethane resin and 40 g of modified carbon fiber into a torque rheometer, knead at 145°C for 20 min, then hot press the material at 145°C for 8 min at 15 MPa in a hot press, and then cold press at room temperature for 5 min at 15 MPa to obtain heat-resistant carbon fiber.

[0040] Example 4

[0041] (1) Add 0.75 g of hydroxyethyl acrylate-TDI semi-addition product, 0.2 g of 2,4,6-tri(ethanolamino)-s-triazine, and 6.9 mg of dibutyltin dilaurate to ethyl acetate, heat to 70°C, stir and react for 4 hours, and distill under reduced pressure. The product is recrystallized from ethyl acetate to obtain a vinyl triazine monomer.

[0042] (2) Add 0.5 g of oxidized carbon fiber, 0.5 g of hydroxyethyl acrylate-TDI semi-addition product, and 0.07 g of dibutyltin dilaurate to 30 mL of toluene, heat to 110° C., stir to react for 8 h, filter, wash with ethanol, and dry to obtain vinyl carbon fiber.

[0043] (3) Add 1 g of vinyl carbon fiber, 4.1 g of vinyl triazine monomer, and 1.12 g of ethylene glycol bis(thioglycolate) to 70 mL of N,N-dimethylacetamide, introduce nitrogen, add 0.05 g of triethylamine, stir and react at room temperature for 6 h, pour the solution into ethanol, filter, wash with ethanol, and dry to obtain modified carbon fiber.

[0044] (4) Add 1 kg of polyurethane resin and 60 g of modified carbon fiber into a torque rheometer, knead at 150 ° C for 20 min, then hot press the material at 150 ° C for 5 min at 15 MPa in a hot press, and then cold press at room temperature for 5 min at 15 MPa to obtain heat-resistant carbon fiber.

[0045] Comparative Example 1

[0046] (1) Add 1 kg of polyurethane resin into the torque rheometer and knead at 145°C for 20 min. Then, heat press the material at 145°C for 8 min at 10 MPa in a hot press and then cold press at room temperature for 10 min at 10 MPa to obtain a polyurethane material.

[0047] Comparative Example 2

[0048] (1) Add 1 kg of polyurethane resin and 10 g of oxidized carbon fiber into a torque rheometer and knead them at 145 ° C for 20 min. Then, place the material in a hot press at 10 MPa and 145 ° C for 8 min, and then cold press at 10 MPa at room temperature for 10 min to obtain heat-resistant carbon fiber.

[0049] Comparative Example 3

[0050] (1) Add 1 kg of polyurethane resin and 10 g of vinyl carbon fiber (prepared in the same manner as in Example 1) into a torque rheometer and knead at 145°C for 20 min. Then, place the material in a hot press at 10 MPa and 145°C for 8 min, and then cold press at 10 MPa and room temperature for 10 min to obtain heat-resistant carbon fiber.

[0051] Comparative Example 4

[0052] (1) Add 1 g of vinyl carbon fiber (prepared in the same manner as in Example 1), 5.2 g of trimethylolpropane triacrylate (CAS registration number 15625-89-5), and 1.58 g of ethylene glycol bis(thioglycolate) to 70 mL of N,N-dimethylacetamide, introduce nitrogen, add 0.07 g of triethylamine, stir and react at room temperature for 12 h, pour the solution into ethanol, filter, wash with ethanol, and dry to obtain modified carbon fiber.

[0053] (2) Add 1 kg of polyurethane resin and 10 g of modified carbon fiber into a torque rheometer, knead at 145 ° C for 20 min, then hot press the material at 145 ° C for 8 min at 10 MPa in a hot press, and then cold press at room temperature for 10 min at 10 MPa to obtain heat-resistant carbon fiber.

[0054] The tensile properties of heat-resistant carbon fiber are tested according to GB / T 1040.1-2018. The heat-resistant carbon fiber is placed in an oven, heat treated at 100°C for 240 hours, cooled to room temperature, and then the tensile properties are tested.

[0055] The flame retardant properties are tested according to GB / T 2406.1-2008 method.

[0056] Table 1 Tensile properties and flame retardant properties of heat-resistant carbon fibers

[0057]

[0058] Table 2 Flame retardant properties of heat-resistant carbon fiber

[0059]

[0060]

[0061] After testing, compared with Comparative Example 1, modified carbon fiber is added to the polyurethane of Examples 1-4, and the surface of the carbon fiber is grafted with a hyperbranched polymer containing a carbamate structural unit, which has good interfacial compatibility with the polyurethane containing a carbamate group, thereby improving the compatibility between the carbon fiber and the polyurethane, improving the dispersibility of the carbon fiber in the polyurethane, making the carbon fiber have a good reinforcement effect, and playing a synergistic enhancement role with the hyperbranched polymer, improving the tensile strength and elongation at break of the polyurethane-based heat-resistant carbon fiber, and the hyperbranched polymer grafted with the carbon fiber contains a heat-resistant triazine functional group, which is conducive to improving the heat resistance of the polyurethane, and after high-temperature heat treatment, the polyurethane-based heat-resistant carbon fiber still maintains good tensile strength and elongation at break. And the nitrogen-rich triazine functional group contained in the hyperbranched polymer can produce a large amount of non-combustible gases such as nitrogen when burning, which is conducive to diluting oxygen and taking away the heat of the combustion system, thereby improving the limiting oxygen index of the polyurethane-based heat-resistant carbon fiber and improving the flame retardant properties.

[0062] The oxidized carbon fiber added in Comparative Example 2 has poor compatibility with the polyurethane resin, low reinforcement effect, low increase in tensile strength and elongation at break of the polyurethane-based heat-resistant carbon fiber, and after high-temperature heat treatment, the tensile strength and elongation at break of the material decrease greatly, the retention rate is low, and the heat resistance is poor. At the same time, the limiting oxygen index is low and the flame retardancy is poor.

[0063] In Comparative Example 3, the surface of the vinyl carbon fiber added is not grafted with a hyperbranched polymer, the reinforcement effect is low, the tensile strength and elongation at break of the material are increased at a low rate, and after high-temperature heat treatment, the tensile strength and elongation at break of the material decrease greatly, the retention rate is low, and the heat resistance is poor. In addition, the limiting oxygen index is low, and the flame retardancy is poor.

[0064] Comparative Example 4 uses trimethylolpropane triacrylate and ethylene glycol dithioacetate as polymerization monomers to carry out a graft polymerization reaction on the surface of vinyl carbon fiber. The hyperbranched polymer grafted on the surface of the modified carbon fiber does not contain a carbamate group, and the interface compatibility with the polyurethane resin is lower than that of the various embodiments, resulting in a lower reinforcement effect. The tensile strength and elongation at break of the material are lower than those of the various embodiments, and the grafted hyperbranched polymer does not contain a triazine functional group. Compared with the heat resistance and flame retardancy of the material, after high-temperature heat treatment, the tensile strength and elongation at break of the material decrease significantly, and the limiting oxygen index is lower.

[0065] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A heat-resistant carbon fiber, characterized in that: The heat-resistant carbon fiber comprises 100 parts by weight of polyurethane resin and 1-6 parts by weight of modified carbon fiber; The preparation method of the modified carbon fiber is: (1) Add oxidized carbon fiber, hydroxyethyl acrylate-TDI semi-addition product, and dibutyltin dilaurate to toluene, heat to 100-110° C., stir and react for 8-12 hours, filter, wash with ethanol, and dry to obtain vinyl carbon fiber; (2) Add vinyl carbon fiber, vinyl triazine monomer, and ethylene glycol bis(thioglycolate) to N,N-dimethylacetamide, introduce nitrogen, add triethylamine, stir and react at room temperature for 6-12 hours, pour the solution into ethanol, filter, wash with ethanol, and dry to obtain modified carbon fiber; The structural formula of the vinyl triazine monomer is as follows:

2. The heat-resistant carbon fiber according to claim 1, characterized in that: In the above (1), the mass of hydroxyethyl acrylate-TDI semi-addition product and dibutyltin dilaurate is 50-200% and 6-28% of the mass of oxidized carbon fiber.

3. The heat-resistant carbon fiber according to claim 1, characterized in that: In the above (2), the weights of vinyl triazine monomer, ethylene glycol bis(thioglycolate) and triethylamine are 220-650%, 65-200% and 3-10% of the weight of the vinyl carbon fiber, respectively.

4. The heat-resistant carbon fiber according to claim 3, characterized in that: The preparation method of the vinyl triazine monomer comprises: adding hydroxyethyl acrylate-TDI semi-addition product, 2,4,6-tri(ethanolamino)-s-triazine and dibutyltin dilaurate into a solvent, stirring for reaction and then performing reduced pressure distillation, and recrystallizing the product with ethyl acetate to obtain the vinyl triazine monomer.

5. The heat-resistant carbon fiber according to claim 4, characterized in that: The solvent is toluene, 1,4-dioxane, ethyl acetate or tetrahydrofuran.

6. The heat-resistant carbon fiber according to claim 4, characterized in that: The patents of the hydroxyethyl acrylate-TDI semi-addition product and dibutyltin dilaurate are 340-400% and (2.7-3.6)% of the mass of 2,4,6-tri(ethanolamino)-s-triazine respectively.

7. The heat-resistant carbon fiber according to claim 4, characterized in that: The reaction temperature is 60-100° C. and the reaction time is 4-8 hours.

8. A method for preparing the heat-resistant carbon fiber according to any one of claims 1 to 7, characterized in that: The preparation method comprises the following steps: adding polyurethane resin and modified carbon fiber into a torque rheometer for internal kneading, and then hot pressing and cold pressing the materials in a hot press to obtain heat-resistant carbon fiber.

9. The heat-resistant carbon fiber according to claim 8, characterized in that: The temperature during the banburying is 145-160° C. and the time is 10-20 minutes.

10. The heat-resistant carbon fiber according to claim 8, characterized in that: The temperature during hot pressing is 145-160° C., the pressure is 10-15 MPa, and the time is 5-8 min; the pressure during cold pressing is 10-15 MPa, and the time is 5-10 min.

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