CN109468843B - Method for grafting hydroxyl-terminated hyperbranched polymer on surface of carbon fiber - Google Patents

Method for grafting hydroxyl-terminated hyperbranched polymer on surface of carbon fiber Download PDF

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CN109468843B
CN109468843B CN201811260450.9A CN201811260450A CN109468843B CN 109468843 B CN109468843 B CN 109468843B CN 201811260450 A CN201811260450 A CN 201811260450A CN 109468843 B CN109468843 B CN 109468843B
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carbon fiber
hydroxyl
temperature
hyperbranched polymer
dimethylacetamide
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CN109468843A (en
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马丽春
石龙龙
宋国君
李培耀
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Qingdao University
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Abstract

A method for grafting hydroxyl-terminated hyperbranched polymer on the surface of carbon fiber relates to a method for modifying the surface of carbon fiber. The invention aims to solve the problems that the interface bonding between carbon fibers and a resin matrix is weak, the synthesis process of a hydroxyl-terminated hyperbranched polymer is complex, the synthesis raw materials are toxic, and the modification of the carbon fibers is restricted. The method comprises the following steps: firstly, preparing hydroxyl-terminated hyperbranched polymer; secondly, extracting carbon fibers; thirdly, oxidizing; and fourthly, grafting to obtain the carbon fiber with the surface grafted with the hydroxyl terminated hyperbranched polymer. Because the hyperbranched polymer with the end capped by hydroxyl has a large number of polar hydroxyl and hole structures, after the hyperbranched polymer is grafted to the surface of carbon fiber, the wettability and the cohesiveness between the carbon fiber and resin are obviously improved, so that the interface performance of the composite material is greatly improved, and the mechanical property and the thermal stability of the composite material are further improved. The invention can obtain a method for grafting hydroxyl-terminated hyperbranched polymer on the surface of carbon fiber.

Description

Method for grafting hydroxyl-terminated hyperbranched polymer on surface of carbon fiber
Technical Field
The invention relates to a method for modifying the surface of carbon fiber.
Background
In recent years, Carbon Fibers (CF) have been widely used as ideal reinforcements for advanced composites due to their high strength, high modulus, and the performance of Carbon Fiber Reinforced Polymer (CFRP) composites is largely dependent on the interfacial properties, with a high quality interface being a guarantee of uniform load transfer from the resin to the carbon fibers. However, the surface of the carbon fiber is smooth and chemically inert, the surface energy is low, the wettability and the cohesiveness with a resin matrix are poor, and the interface performance and other performances of the composite material are finally influenced, so that the surface treatment of the carbon fiber is vital to the development of a reinforced material of the carbon fiber, the interface bonding between the unmodified carbon fiber and the resin matrix is weak at present, the interface shear strength of the unmodified carbon fiber composite material is about 49MPa, and therefore the surface of the carbon fiber needs to be modified, the surface modification technology of the carbon fiber at present mainly comprises a surface oxidation technology, a chemical vapor deposition technology, a surface coating technology and the like, the wettability of the carbon fiber and the resin can be basically improved by the methods, and the problems of complex production process, high cost, long reaction time and the like exist. Therefore, at present, the method aims to find a carbon fiber surface modification method which is mild in condition, green, environment-friendly and efficient, and aims to avoid the decrease of the strength of a monofilament fiber body and simultaneously form more active sites on the surface of the monofilament fiber so as to improve the interface bonding strength of the carbon fiber and resin.
The graft polymer technology is a new research direction, and is to graft macromolecules on the surface of carbon fibers to improve the surface activity and roughness of the carbon fibers and further improve the interface bonding performance of the carbon fibers. The hydroxyl-terminated hyperbranched polymer (HTHBP) has a large amount of terminal polar hydroxyl groups, a pore structure and high resin compatibility, so that the hydroxyl-terminated hyperbranched polymer not only provides a large amount of active sites capable of reacting with carbon fibers and a resin matrix, but also can promote the reaction of a curing agent and epoxy resin, so that the hydroxyl-terminated hyperbranched polymer can be an ideal material for functionalized carbon fibers, but also has the problems of complex synthesis process, toxic synthesis raw materials and the like.
Disclosure of Invention
The invention aims to solve the problems that the interface bonding between carbon fibers and a resin matrix is weak, the synthesis process of a hydroxyl-terminated hyperbranched polymer is complex, the synthesis raw materials are toxic, and the modification of the carbon fibers is restricted, and provides a method for grafting the hydroxyl-terminated hyperbranched polymer on the surface of the carbon fibers.
A method for grafting hydroxyl-terminated hyperbranched polymer on the surface of carbon fiber is completed according to the following steps:
firstly, preparing hydroxyl-terminated hyperbranched polymer:
adding isophorone diisocyanate and N, N-dimethylacetamide into a glass container to obtain an isophorone diisocyanate solution; then placing the glass container filled with the isophorone diisocyanate solution in an ice water bath at 0-5 ℃;
the volume ratio of the mass of the isophorone diisocyanate to the volume of the N, N-dimethyl acetamide in the first step (6 g-12 g) is 50 mL;
adding the tris into N, N-dimethylacetamide, and then carrying out ultrasonic mixing for 10-20 min to obtain tris solution;
the volume ratio of the mass of the trihydroxymethyl aminomethane to the volume of the N, N-dimethylacetamide in the step one is (3 g-6 g) to 50 mL;
thirdly, stirring the isophorone diisocyanate solution in the glass container of the ice water bath at the temperature of 0-5 ℃ in the first step at the stirring speed of 300-400 r/min, and then dripping the tris (hydroxymethyl) aminomethane solution into the isophorone diisocyanate solution at the temperature of 0-5 ℃ at the dripping speed of 10-15 drops/min at the stirring speed of 300-400 r/min to obtain a reaction solution I;
the volume ratio of the isophorone diisocyanate solution to the tris solution in the first step is 1: 1;
heating the temperature of the reaction liquid I to 5-10 ℃, stirring and reacting for 5-6 h at the temperature of 5-10 ℃, heating the temperature of the reaction liquid I to 35-40 ℃, adding dibutyltin dilaurate into the reaction liquid I at the temperature of 35-40 ℃, and stirring and reacting for 10-15 h at the temperature of 35-40 ℃ and the stirring speed of 300-400 r/min to obtain a reaction liquid II;
the volume ratio of the mass of the dibutyltin dilaurate to the reaction liquid I in the first step (0.08 g-0.12 g) is 100 mL;
fifthly, adding the reaction liquid II into deionized water to precipitate, standing for 25-30 min, and centrifuging at the centrifugal speed of 6000-8000 r/min to obtain a solid reaction product;
sixthly, washing the solid reaction product for 3 to 5 times by using deionized water, then putting the solid reaction product washed by the deionized water into a freeze dryer, and freeze-drying for 36 to 48 hours at the temperature of minus 10 to minus 5 ℃ to obtain a dry white solid substance, namely the hydroxyl-terminated hyperbranched polymer;
secondly, extraction treatment of carbon fibers:
putting carbon fibers into a Soxhlet extractor filled with acetone, heating the acetone to 75-85 ℃, continuously evaporating the acetone and condensing in the Soxhlet extractor to continuously wash impurities on the surfaces of the carbon fibers in the distilled acetone for 48-72 hours, and taking out the carbon fibers to obtain the carbon fibers with the impurities on the surfaces removed; taking out the carbon fiber with the surface impurities removed, and then placing the carbon fiber in a drying oven at the temperature of 70-80 ℃ for drying for 2-4 h to obtain the carbon fiber after extraction treatment;
thirdly, oxidation:
soaking the extracted carbon fiber into a potassium persulfate/silver nitrate mixed water solution, heating to 60-80 ℃, and keeping the temperature at 60-80 ℃ for 1-2 hours to obtain oxidized carbon fiber; the concentration of the potassium persulfate in the potassium persulfate/silver nitrate mixed water solution is 0.1-0.2 mol/L; the concentration of silver nitrate in the potassium persulfate/silver nitrate mixed water solution is 0.0001-0.05 mol/L;
the volume ratio of the mass of the carbon fiber after extraction treatment to the potassium persulfate/silver nitrate mixed water solution in the third step is (0.3 g-1.5 g) to (300 mL-500 mL);
soaking the oxidized carbon fiber obtained in the third step in distilled water for 5-10 min at room temperature, taking out the carbon fiber soaked in the distilled water, and removing the distilled water;
the volume ratio of the mass of the oxidized carbon fiber to the distilled water in the third step is (0.3 g-1.5 g): 300 mL-500 mL;
thirdly, repeating the third step and the third step for 3 to 5 times to obtain the oxidized carbon fiber cleaned by the distilled water;
fourthly, drying the oxidized carbon fiber cleaned by the distilled water obtained in the third step for 2 to 4 hours at the temperature of between 70 and 80 ℃ to obtain the dried oxidized carbon fiber;
fifthly, placing the dried oxidized carbon fiber obtained in the third step in a Soxhlet extractor filled with absolute ethyl alcohol, and cleaning the oxidized carbon fiber with the absolute ethyl alcohol at the temperature of 90-100 ℃ for 2-4 h to obtain the oxidized carbon fiber cleaned with the absolute ethyl alcohol;
sixthly, drying the oxidized carbon fiber washed by the absolute ethyl alcohol obtained in the third step for 2-4 hours at the temperature of 70-80 ℃ to obtain dried oxidized carbon fiber;
fourthly, grafting:
adding a hydroxyl-terminated hyperbranched polymer into N, N-dimethylacetamide, performing ultrasonic dispersion for 15-30 min, adding dried oxidized carbon fiber, 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride and 4-dimethylaminopyridine, and finally stirring and refluxing for 12-24 h at the temperature of 100-150 ℃ and the stirring speed of 300-400 r/min to obtain the treated carbon fiber;
the mass ratio of the hydroxyl-terminated hyperbranched polymer to the volume of the N, N-dimethylacetamide in the step IV is (1 g-1.5 g): 30 mL-60 mL;
the mass ratio of the dry oxidized carbon fiber to the volume of the N, N-dimethylacetamide in the step IV is (1.0-2.0 g): (30-60 mL);
the volume ratio of the mass of the 1-ethyl- (3-dimethylaminopropyl) carbonyldiimine hydrochloride to the volume of the N, N-dimethylacetamide in the fourth step is (0.5 g-1.0 g): 30 mL-60 mL;
the mass ratio of the 4-dimethylaminopyridine to the N, N-dimethylacetamide in the fourth step is (0.05-0.1 g): 30-60 mL);
secondly, taking out the treated carbon fiber and then immersing the carbon fiber into distilled water for 10-15 min;
thirdly, the step IV is circulated for 3 to 5 times to obtain the treated carbon fiber cleaned by the distilled water;
putting the treated carbon fiber cleaned by the distilled water into a Soxhlet extractor filled with absolute ethyl alcohol, and cleaning the treated carbon fiber cleaned by the distilled water by using the absolute ethyl alcohol at the temperature of 90-100 ℃ for 2-4 h to obtain the treated carbon fiber cleaned by the absolute ethyl alcohol;
and fifthly, drying the treated carbon fiber cleaned by the absolute ethyl alcohol in an oven at the temperature of 75-80 ℃ for 3-5 h to obtain the carbon fiber with the surface grafted with the hydroxyl terminated hyperbranched polymer.
The principle and the advantages of the invention are as follows:
firstly, the invention uses nontoxic and high-activity tris (hydroxymethyl) aminomethane (TOAM) as a synthesis raw material, greatly shortens the synthesis time and reduces the environmental pollution;
secondly, grafting the hydroxyl-terminated hyperbranched polymer to the surface of the carbon fiber by adopting a covalent grafting method to prepare the carbon fiber which not only contains a large number of polar terminal hydroxyl groups on the surface but also is easy to form covalent bonds with a matrix;
thirdly, because the hyperbranched polymer with the end capped by hydroxyl has a large number of polar hydroxyl groups and hole structures, after the hyperbranched polymer is grafted to the surface of the carbon fiber, the wettability and the cohesiveness between the carbon fiber and resin are obviously improved, so that the interface performance of the composite material is greatly improved, and the mechanical property and the thermal stability of the composite material are further improved;
fourthly, the interfacial shear strength (IFSS) of the carbon fiber of the surface grafted hydroxyl-terminated hyperbranched polymer prepared by the method is improved to 60.9-87.8 MP from 48.8MPa of the precursor (the carbon fiber which is not grafted), and is improved by 25-79.9%; the interlaminar shear strength (ILSS) is increased from 58.6MPa of protofilament (ungrafted carbon fiber) to 69.7-81.8 MPa, and is increased by 19-39.6%.
The invention can obtain a method for grafting hydroxyl-terminated hyperbranched polymer on the surface of carbon fiber.
Drawings
FIG. 1 is an XPS spectrum of an extracted carbon fiber obtained in the second step of the example;
FIG. 2 is the peak separation diagram of FIG. 1, wherein 1 is C1s (1), 2 is C1s (2), and 3 is C1s (3);
FIG. 3 is an XPS spectrum of a carbon fiber with a surface grafted with a hydroxyl terminated hyperbranched polymer obtained in the fourth step of the example;
fig. 4 is the peak separation chart of fig. 3, wherein 4 is C-N, 5 is C-O, 6 is C ═ O, and 7 is NCOO;
FIG. 5 is an SEM image of an extracted carbon fiber obtained in step two of the example;
FIG. 6 is an SEM image of carbon fibers with hydroxyl-terminated hyperbranched polymer grafted on the surface thereof obtained in the fourth step of the example;
FIG. 7 is a bar graph of interfacial shear strength, in which 1 is the interfacial shear strength of the carbon fiber after extraction treatment obtained in the third step of the example, and 2 is the interfacial shear strength of the carbon fiber with the surface grafted with the hydroxyl-terminated hyperbranched polymer obtained in the fourth step of the example;
fig. 8 is a bar graph of interlaminar shear strength, in which 1 is the interlaminar shear strength of the carbon fiber after extraction treatment obtained in the third step of the example, and 2 is the interlaminar shear strength of the carbon fiber with the surface grafted with the hydroxyl-terminated hyperbranched polymer obtained in the fourth step of the example.
Detailed Description
The first embodiment is as follows: the embodiment is a method for grafting hydroxyl-terminated hyperbranched polymer on the surface of carbon fiber, which is completed according to the following steps:
firstly, preparing hydroxyl-terminated hyperbranched polymer:
adding isophorone diisocyanate and N, N-dimethylacetamide into a glass container to obtain an isophorone diisocyanate solution; then placing the glass container filled with the isophorone diisocyanate solution in an ice water bath at 0-5 ℃;
the volume ratio of the mass of the isophorone diisocyanate to the volume of the N, N-dimethyl acetamide in the first step (6 g-12 g) is 50 mL;
adding the tris into N, N-dimethylacetamide, and then carrying out ultrasonic mixing for 10-20 min to obtain tris solution;
the volume ratio of the mass of the trihydroxymethyl aminomethane to the volume of the N, N-dimethylacetamide in the step one is (3 g-6 g) to 50 mL;
thirdly, stirring the isophorone diisocyanate solution in the glass container of the ice water bath at the temperature of 0-5 ℃ in the first step at the stirring speed of 300-400 r/min, and then dripping the tris (hydroxymethyl) aminomethane solution into the isophorone diisocyanate solution at the temperature of 0-5 ℃ at the dripping speed of 10-15 drops/min at the stirring speed of 300-400 r/min to obtain a reaction solution I;
the volume ratio of the isophorone diisocyanate solution to the tris solution in the first step is 1: 1;
heating the temperature of the reaction liquid I to 5-10 ℃, stirring and reacting for 5-6 h at the temperature of 5-10 ℃, heating the temperature of the reaction liquid I to 35-40 ℃, adding dibutyltin dilaurate into the reaction liquid I at the temperature of 35-40 ℃, and stirring and reacting for 10-15 h at the temperature of 35-40 ℃ and the stirring speed of 300-400 r/min to obtain a reaction liquid II;
the volume ratio of the mass of the dibutyltin dilaurate to the reaction liquid I in the first step (0.08 g-0.12 g) is 100 mL;
fifthly, adding the reaction liquid II into deionized water to precipitate, standing for 25-30 min, and centrifuging at the centrifugal speed of 6000-8000 r/min to obtain a solid reaction product;
sixthly, washing the solid reaction product for 3 to 5 times by using deionized water, then putting the solid reaction product washed by the deionized water into a freeze dryer, and freeze-drying for 36 to 48 hours at the temperature of minus 10 to minus 5 ℃ to obtain a dry white solid substance, namely the hydroxyl-terminated hyperbranched polymer;
secondly, extraction treatment of carbon fibers:
putting carbon fibers into a Soxhlet extractor filled with acetone, heating the acetone to 75-85 ℃, continuously evaporating the acetone and condensing in the Soxhlet extractor to continuously wash impurities on the surfaces of the carbon fibers in the distilled acetone for 48-72 hours, and taking out the carbon fibers to obtain the carbon fibers with the impurities on the surfaces removed; taking out the carbon fiber with the surface impurities removed, and then placing the carbon fiber in a drying oven at the temperature of 70-80 ℃ for drying for 2-4 h to obtain the carbon fiber after extraction treatment;
thirdly, oxidation:
soaking the extracted carbon fiber into a potassium persulfate/silver nitrate mixed water solution, heating to 60-80 ℃, and keeping the temperature at 60-80 ℃ for 1-2 hours to obtain oxidized carbon fiber; the concentration of the potassium persulfate in the potassium persulfate/silver nitrate mixed water solution is 0.1-0.2 mol/L; the concentration of silver nitrate in the potassium persulfate/silver nitrate mixed water solution is 0.0001-0.05 mol/L;
the volume ratio of the mass of the carbon fiber after extraction treatment to the potassium persulfate/silver nitrate mixed water solution in the third step is (0.3 g-1.5 g) to (300 mL-500 mL);
soaking the oxidized carbon fiber obtained in the third step in distilled water for 5-10 min at room temperature, taking out the carbon fiber soaked in the distilled water, and removing the distilled water;
the volume ratio of the mass of the oxidized carbon fiber to the distilled water in the third step is (0.3 g-1.5 g): 300 mL-500 mL;
thirdly, repeating the third step and the third step for 3 to 5 times to obtain the oxidized carbon fiber cleaned by the distilled water;
fourthly, drying the oxidized carbon fiber cleaned by the distilled water obtained in the third step for 2 to 4 hours at the temperature of between 70 and 80 ℃ to obtain the dried oxidized carbon fiber;
fifthly, placing the dried oxidized carbon fiber obtained in the third step in a Soxhlet extractor filled with absolute ethyl alcohol, and cleaning the oxidized carbon fiber with the absolute ethyl alcohol at the temperature of 90-100 ℃ for 2-4 h to obtain the oxidized carbon fiber cleaned with the absolute ethyl alcohol;
sixthly, drying the oxidized carbon fiber washed by the absolute ethyl alcohol obtained in the third step for 2-4 hours at the temperature of 70-80 ℃ to obtain dried oxidized carbon fiber;
fourthly, grafting:
adding a hydroxyl-terminated hyperbranched polymer into N, N-dimethylacetamide, performing ultrasonic dispersion for 15-30 min, adding dried oxidized carbon fiber, 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride and 4-dimethylaminopyridine, and finally stirring and refluxing for 12-24 h at the temperature of 100-150 ℃ and the stirring speed of 300-400 r/min to obtain the treated carbon fiber;
the mass ratio of the hydroxyl-terminated hyperbranched polymer to the volume of the N, N-dimethylacetamide in the step IV is (1 g-1.5 g): 30 mL-60 mL;
the mass ratio of the dry oxidized carbon fiber to the volume of the N, N-dimethylacetamide in the step IV is (1.0-2.0 g): (30-60 mL);
the volume ratio of the mass of the 1-ethyl- (3-dimethylaminopropyl) carbonyldiimine hydrochloride to the volume of the N, N-dimethylacetamide in the fourth step is (0.5 g-1.0 g): 30 mL-60 mL;
the mass ratio of the 4-dimethylaminopyridine to the N, N-dimethylacetamide in the fourth step is (0.05-0.1 g): 30-60 mL);
secondly, taking out the treated carbon fiber and then immersing the carbon fiber into distilled water for 10-15 min;
thirdly, the step IV is circulated for 3 to 5 times to obtain the treated carbon fiber cleaned by the distilled water;
putting the treated carbon fiber cleaned by the distilled water into a Soxhlet extractor filled with absolute ethyl alcohol, and cleaning the treated carbon fiber cleaned by the distilled water by using the absolute ethyl alcohol at the temperature of 90-100 ℃ for 2-4 h to obtain the treated carbon fiber cleaned by the absolute ethyl alcohol;
and fifthly, drying the treated carbon fiber cleaned by the absolute ethyl alcohol in an oven at the temperature of 75-80 ℃ for 3-5 h to obtain the carbon fiber with the surface grafted with the hydroxyl terminated hyperbranched polymer.
The principle and advantages of the embodiment are as follows:
firstly, the embodiment uses nontoxic and high-activity tris (hydroxymethyl) aminomethane (TOAM) as a synthesis raw material, so that the synthesis time is greatly shortened, and the environmental pollution is reduced;
secondly, grafting the hydroxyl-terminated hyperbranched polymer to the surface of the carbon fiber by adopting a covalent grafting method to prepare the carbon fiber which not only contains a large number of polar terminal hydroxyl groups on the surface but also is easy to form covalent bonds with a matrix;
thirdly, because the hyperbranched polymer with the end capped by hydroxyl has a large number of polar hydroxyl groups and hole structures, after the hyperbranched polymer is grafted to the surface of the carbon fiber, the wettability and the cohesiveness between the carbon fiber and resin are obviously improved, so that the interface performance of the composite material is greatly improved, and the mechanical property and the thermal stability of the composite material are further improved;
fourthly, the interfacial shear strength (IFSS) of the carbon fiber with the surface grafted with the hydroxyl-terminated hyperbranched polymer prepared by the embodiment is improved to 60.9-87.8 MP from 48.8MPa of the precursor (the carbon fiber which is not grafted), and is improved by 25-79.9%; the interlaminar shear strength (ILSS) is increased from 58.6MPa of protofilament (ungrafted carbon fiber) to 69.7-81.8 MPa, and is increased by 19-39.6%.
The embodiment can obtain the method for grafting the hydroxyl-terminated hyperbranched polymer on the surface of the carbon fiber.
The second embodiment is as follows: the present embodiment differs from the present embodiment in that: the volume ratio of the mass of the isophorone diisocyanate to the volume of the N, N-dimethyl acetamide in the first step (I) is (10 g-12 g) 50 mL. Other steps are the same as in the first embodiment.
The third concrete implementation mode: the present embodiment differs from the first or second embodiment in that: the volume ratio of the mass of the trihydroxymethyl aminomethane to the volume of the N, N-dimethylacetamide in the step one is (5 g-6 g):50 mL. The other steps are the same as in the first or second embodiment.
The fourth concrete implementation mode: the difference between this embodiment and one of the first to third embodiments is as follows: the volume ratio of the mass of the dibutyltin dilaurate to the reaction liquid I in the first step (0.1 g-0.12 g) is 100 mL. The other steps are the same as those in the first to third embodiments.
The fifth concrete implementation mode: the difference between this embodiment and one of the first to fourth embodiments is: the mass ratio of the hydroxyl-terminated hyperbranched polymer to the volume of the N, N-dimethylacetamide in the step IV is (1.2 g-1.5 g): 45 mL-60 mL. The other steps are the same as those in the first to fourth embodiments.
The sixth specific implementation mode: the difference between this embodiment and one of the first to fifth embodiments is as follows: the ultrasonic power in the first step is 343-346.5W. The other steps are the same as those in the first to fifth embodiments.
The seventh embodiment: the difference between this embodiment and one of the first to sixth embodiments is: and the volume ratio of the mass of the dried oxidized carbon fiber to the volume of the N, N-dimethylacetamide in the step IV is (1.5-2.0 g): 30-60 mL. The other steps are the same as those in the first to sixth embodiments.
The specific implementation mode is eight: the difference between this embodiment and one of the first to seventh embodiments is: the volume ratio of the mass of the 1-ethyl- (3-dimethylaminopropyl) carbonyldiimine hydrochloride to the volume of the N, N-dimethylacetamide in the fourth step is (0.5 g-0.67 g):50 mL-60 mL. The other steps are the same as those in the first to seventh embodiments.
The specific implementation method nine: the difference between this embodiment and the first to eighth embodiments is: and fourthly, the ultrasonic power in the fourth step is 343W-346.5W. The other steps are the same as those in the first to eighth embodiments.
The detailed implementation mode is ten: the difference between this embodiment and one of the first to ninth embodiments is as follows: the mass ratio of the 4-dimethylaminopyridine to the N, N-dimethylacetamide in the fourth step is (0.05-0.067 g) to (50-60 mL). The other steps are the same as those in the first to ninth embodiments.
The following examples were used to demonstrate the beneficial effects of the present invention:
the first embodiment is as follows: the method for grafting the hydroxyl-terminated hyperbranched polymer on the surface of the carbon fiber is completed according to the following steps:
firstly, preparing hydroxyl-terminated hyperbranched polymer:
adding 12g of isophorone diisocyanate and 50mL of N, N-dimethylacetamide into a three-neck flask to obtain an isophorone diisocyanate solution; then placing the glass container filled with the isophorone diisocyanate solution in an ice water bath at 0 ℃;
adding 6g of tris (hydroxymethyl) aminomethane into 50mL of N, N-dimethylacetamide, and ultrasonically mixing for 20min under the ultrasonic power of 346.5W to obtain tris (hydroxymethyl) aminomethane solution;
thirdly, stirring the isophorone diisocyanate solution in the glass container placed in the ice water bath at 0 ℃ in the first step at the stirring speed of 400r/min, and then dripping the tris (hydroxymethyl) aminomethane solution obtained in the first step at the dripping speed of 15 drops/min into the isophorone diisocyanate solution at the temperature of 0 ℃ and at the stirring speed of 400r/min to obtain a reaction solution I;
heating the temperature of the reaction liquid I to 5 ℃, stirring the reaction liquid I at the temperature of 5 ℃ for 6 hours, heating the temperature of the reaction liquid I to 40 ℃, adding 0.1g of dibutyltin dilaurate into the reaction liquid I at the temperature of 40 ℃, and finally stirring the reaction liquid I at the temperature of 40 ℃ and the stirring speed of 400r/min for 15 hours to obtain a reaction liquid II;
fifthly, adding the reaction liquid II obtained in the first step to 500mL of deionized water to precipitate, standing for 30min, and centrifuging at the centrifugal speed of 8000r/min to obtain a solid reaction product;
sixthly, washing the solid reaction product for 5 times by using deionized water, then putting the solid reaction product washed by the deionized water into a freeze dryer, and freeze-drying for 48 hours at the temperature of minus 10 ℃ to obtain a dry white solid substance, namely the hydroxyl-terminated hyperbranched polymer;
secondly, extraction treatment of carbon fibers:
putting carbon fibers into a Soxhlet extractor filled with acetone, heating the acetone to 82 ℃, continuously evaporating the acetone, condensing the acetone in the Soxhlet extractor, continuously cleaning impurities on the surfaces of the carbon fibers in the distilled acetone for 72 hours, and taking out the carbon fibers to obtain the carbon fibers with the impurities on the surfaces removed; taking out the carbon fiber with the surface impurities removed, and then placing the carbon fiber in an oven at the temperature of 70 ℃ for drying for 4 hours to obtain the carbon fiber after extraction treatment;
thirdly, oxidation:
soaking the extracted carbon fiber into a potassium persulfate/silver nitrate mixed water solution, heating to 70 ℃, and keeping the temperature at 70 ℃ for 1h to obtain oxidized carbon fiber; the concentration of potassium persulfate in the potassium persulfate/silver nitrate mixed water solution is 0.1 mol/L; the concentration of silver nitrate in the potassium persulfate/silver nitrate mixed water solution is 0.01 mol/L;
the volume ratio of the mass of the carbon fiber after extraction treatment to the potassium persulfate/silver nitrate mixed water solution in the third step is 1.5g:500 mL;
soaking the oxidized carbon fibers obtained in the third step in distilled water for 10min at room temperature, taking out the carbon fibers soaked in the distilled water, and removing the distilled water;
the volume ratio of the mass of the oxidized carbon fiber to the distilled water in the third step is 1.5g:500 mL;
thirdly, repeating the third step and the second step for 5 times to obtain oxidized carbon fibers cleaned by distilled water;
fourthly, drying the oxidized carbon fiber cleaned by the distilled water obtained in the third step for 4 hours at the temperature of 70 ℃ to obtain the dried oxidized carbon fiber;
fifthly, placing the dried oxidized carbon fiber obtained in the third step in a Soxhlet extractor filled with absolute ethyl alcohol, and cleaning the oxidized carbon fiber with the absolute ethyl alcohol at the temperature of 90 ℃ for 2 hours to obtain the oxidized carbon fiber cleaned with the absolute ethyl alcohol;
sixthly, drying the oxidized carbon fiber washed by the absolute ethyl alcohol obtained in the third fifth step for 4 hours at the temperature of 70 ℃ to obtain dried oxidized carbon fiber;
fourthly, grafting:
adding 1.5g of hydroxyl-terminated hyperbranched polymer into 60mL of N, N-dimethylacetamide, performing ultrasound for 30min at the ultrasonic power of 346.5W, then adding 1.5g of dried oxidized carbon fiber, 0.67g of 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride and 0.067g of 4-dimethylaminopyridine, and finally stirring and refluxing for 24h at the temperature of 100 ℃ and the stirring speed of 400r/min to obtain the treated carbon fiber;
② taking out the treated carbon fiber and then immersing the carbon fiber into distilled water for 15 min;
thirdly, circulating the step IV and the step III for 5 times to obtain the treated carbon fiber cleaned by the distilled water;
putting the treated carbon fiber cleaned by the distilled water into a Soxhlet extractor filled with absolute ethyl alcohol, and cleaning the treated carbon fiber cleaned by the distilled water by using the absolute ethyl alcohol at the temperature of 90 ℃ for 2 hours to obtain the treated carbon fiber cleaned by the absolute ethyl alcohol;
and fifthly, drying the treated carbon fiber cleaned by the absolute ethyl alcohol in an oven at the temperature of 80 ℃ for 4 hours to obtain the carbon fiber with the surface grafted with the hydroxyl-terminated hyperbranched polymer, which is expressed as CF-HTHBP.
FIG. 1 is an XPS spectrum of an extracted carbon fiber obtained in the second step of the example;
FIG. 2 is the peak separation diagram of FIG. 1, wherein 1 is C1s (1), 2 is C1s (2), and 3 is C1s (3);
FIG. 3 is an XPS spectrum of a carbon fiber with a surface grafted with a hydroxyl terminated hyperbranched polymer obtained in the fourth step of the example;
fig. 4 is the peak separation chart of fig. 3, wherein 4 is C-N, 5 is C-O, 6 is C ═ O, and 7 is NCOO;
table 1 shows the element content changes before and after the carbon fiber modification. After the surface of the carbon fiber is grafted with the hydroxyl-terminated hyperbranched polymer (HTHBP), the O content is obviously increased and is improved to 20.19 percent from untreated 3.32 percent. As can be seen from the peak separation plot of CF-HTHBP, a new NCOO peak appears at a binding energy of 289eV, and these results indicate that the hydroxyl-terminated hyperbranched polymer (HTHBP) has been covalently grafted to the surface of the carbon fiber, i.e. the hydroxyl groups in the HTHBP and the carboxyl groups in the oxidized carbon fiber react to form ester bonds, the relative content of which is 4.67%.
TABLE 1
Figure BDA0001843776130000111
Note: CF is the carbon fiber obtained in the third step of the example after extraction treatment, and CF-HTHBP is the carbon fiber obtained in the fourth and fifth step of the example and with the surface grafted with hydroxyl-terminated hyperbranched polymer.
FIG. 5 is an SEM image of an extracted carbon fiber obtained in step two of the example;
FIG. 6 is an SEM image of carbon fibers with hydroxyl-terminated hyperbranched polymer grafted on the surface thereof obtained in the fourth step of the example;
as can be seen from fig. 5 to 6, the surface of the carbon fiber that is not grafted (the carbon fiber after the extraction treatment obtained in the third step of the example) is smooth. And the surface of the carbon fiber (CF-HTHBP) grafted with the hydroxyl-terminated hyperbranched polymer obtained in the fourth and fifth step of the embodiment forms a layer of covering, because the hydroxyl-terminated hyperbranched polymer (HTHBP) is uniformly and covalently grafted on the surface of the carbon fiber, the surface roughness and the specific surface area of the fiber are improved, the mechanical interlocking effect and the physical entanglement density between the fiber and the resin are increased, and thus interface bonding with higher bonding strength is formed.
Table 2 shows the changes of the contact angle and the surface energy of the Carbon Fiber (CF) after the extraction treatment obtained in the third step of the example and the carbon fiber (CF-HTHBP) with the surface grafted with the hydroxyl terminated hyperbranched polymer obtained in the fourth step of the example, and it can be found from table 2 that the contact angle in water and diiodomethane is significantly reduced after the carbon fiber is grafted with the HTHBP, the polar component, the dispersion component and the surface energy are correspondingly improved, and the surface energy is improved by 104.2% from 29.97mN/m to 61.19 mN/m. This shows that the grafting of HTHBP to the surface of carbon fiber greatly improves the polar group and roughness of the surface of the fiber, thereby obviously improving the wettability of the surface of the carbon fiber and resin.
TABLE 2
Figure BDA0001843776130000112
Interfacial shear strength test (one):
in the experiment, an interface evaluation apparatus for FA620 type composite material (Tortoise corporation, Japan) was used. Firstly, firmly sticking a carbon fiber monofilament on a metal support by using a double-sided adhesive tape, weighing and uniformly mixing epoxy resin E-51 and a curing agent H-256 in a mass ratio of 100:32, dipping a drop of the epoxy resin on the surface of the carbon fiber monofilament by using a steel needle, forming resin microdroplets by the epoxy resin under the action of surface tension, and then respectively keeping constant temperature at 90 ℃, 120 ℃ and 150 ℃ for 2H, 2H and 3H for curing to prepare the carbon fiber/epoxy resin microdroplet composite material. In the testing process, resin droplets with the diameter of about 80 microns are selected as a testing object, the diameter of the resin spheres is too large, the fibers are easily broken, the resin spheres are not separated from the fibers, if the resin spheres are too small, the edges of equipment cannot be clamped, the edges of the resin spheres slide through the testing process without the action of force, the load loading speed is 0.5 microns s < -1 >, 50 effective data are measured from each group of samples, and the average value of the effective data is calculated, wherein the carbon fibers are extracted Carbon Fibers (CF) obtained in the second step and the third step of the embodiment. The interfacial shear strength (IFSS) can be obtained according to equation (1):
Figure BDA0001843776130000121
in the formula Fmax-peak load value (N) at fiber pull-out;
d-fiber filament diameter (m);
l-epoxy microdroplet embedding length (m).
Testing the interfacial shear strength of the Carbon Fiber (CF) after extraction treatment obtained in the second step of the embodiment;
interfacial shear strength test (ii): the difference between the test and the interface shear strength test (I) is as follows: the carbon fiber is the carbon fiber (CF-HTHBP) with the surface grafted with the hydroxyl-terminated hyperbranched polymer obtained in the fourth and fifth step of the embodiment. The other steps and test methods are the same as the interfacial shear strength test (one).
The results of the interfacial shear strength test (one) and the interfacial shear strength test (two) are shown in fig. 7;
FIG. 7 is a bar graph of interfacial shear strength, in which 1 is the interfacial shear strength of the carbon fiber after extraction treatment obtained in the third step of the example, and 2 is the interfacial shear strength of the carbon fiber with the surface grafted with the hydroxyl-terminated hyperbranched polymer obtained in the fourth step of the example;
as can be seen from FIG. 7, the interfacial shear strength (IFSS) of the carbon fiber grafted with HTHBP is increased from 48.8MPa of the precursor to 87.8MPa, and is increased by 79.9%.
Interlaminar shear strength test (one):
in the experiment, the ILSS of the carbon fiber composite material is tested by a three-point bending method on an electronic universal tester GT-7000-A2X (Taiwan). Firstly, winding 20 circles of carbon fibers on a frame with the length of 20cm, then weighing and uniformly mixing epoxy resin E-51 and a curing agent H-256 with the mass ratio of 100:32, then fully soaking the carbon fibers with matrix resin, then placing the carbon fibers into a mold, placing the mold into a vacuum drying oven for vacuum defoaming, then placing the mold onto a hot press for curing according to the following process, and respectively keeping the mold at constant temperature of 90 ℃, 120 ℃ and 150 ℃ for 2H, 2H and 3H for curing, thereby preparing the carbon fiber/epoxy resin composite material. During the test, the specimen size was 20mm × 6mm × 2mm, the specimen span-to-thickness ratio was 5, and the load application rate was 2mm · min-1The test is carried out at room temperature, 50 effective data are measured and the average value of the effective data is calculated for each group of samples, and the carbon fiber is the Carbon Fiber (CF) obtained after extraction treatment in the second step of the embodiment. The interlaminar shear strength (ILSS) can be obtained according to equation (2):
Figure BDA0001843776130000131
wherein F is the maximum load (N) at fault;
b-sample cross-sectional width (mm);
h-thickness of cross section of the specimen (mm).
Testing the interlaminar shear strength of the extracted Carbon Fiber (CF) obtained in the second step of the embodiment according to the method;
interlaminar shear strength test (ii): the difference between the test and the interlaminar shear strength test (I) is as follows: the carbon fiber is the carbon fiber (CF-HTHBP) with the surface grafted with the hydroxyl-terminated hyperbranched polymer obtained in the fourth and fifth step of the embodiment. The other steps and test methods are the same as the interlaminar shear strength test (one).
The results of the interlaminar shear strength test (one) and the interlaminar shear strength test (two) are shown in fig. 8;
fig. 8 is a bar graph of interlaminar shear strength, in which 1 is the interlaminar shear strength of the carbon fiber after extraction treatment obtained in the third step of the example, and 2 is the interlaminar shear strength of the carbon fiber with the surface grafted with the hydroxyl-terminated hyperbranched polymer obtained in the fourth step of the example.
As can be seen from FIG. 8, the interlaminar shear strength (ILSS) after grafting of HTHBP onto carbon fiber was increased from 58.6MPa to 81.8MPa, which is 39.6% higher than that of the precursor.
The interface shear strength and the interlaminar shear strength of the carbon fiber with the hydroxyl-terminated hyperbranched polymer grafted on the surface are greatly improved in the fourth step and the fifth step of the embodiment, because the surface of the carbon fiber contains a large amount of polar hydroxyl groups after being grafted with the HTHBP and can participate in chemical reaction with resin groups. Meanwhile, the increase of the surface roughness of the carbon fibers can enhance the mechanical interlocking effect and the physical entanglement density of the fibers and the resin, so that the carbon fiber reinforced composite material has better interface combination, which is beneficial to the improvement of the interface performance of the final composite material.
Example two: the method for grafting the hydroxyl-terminated hyperbranched polymer on the surface of the carbon fiber is completed according to the following steps:
firstly, preparing hydroxyl-terminated hyperbranched polymer:
adding 6g of isophorone diisocyanate and 50mL of N, N-dimethylacetamide into a three-neck flask to obtain an isophorone diisocyanate solution; then placing the glass container filled with the isophorone diisocyanate solution in an ice water bath at 5 ℃;
adding 3g of tris (hydroxymethyl) aminomethane into 50mL of N, N-dimethylacetamide, and ultrasonically mixing for 10min at the ultrasonic power of 343W to obtain tris (hydroxymethyl) aminomethane solution;
thirdly, stirring the isophorone diisocyanate solution in the glass container placed in the ice water bath at the temperature of 5 ℃ in the first step at the stirring speed of 300r/min, and then dripping the tris (hydroxymethyl) aminomethane solution obtained in the first step at the dripping speed of 15 drops/min into the isophorone diisocyanate solution at the temperature of 5 ℃ at the stirring speed of 300r/min to obtain a reaction solution I;
heating the temperature of the reaction liquid I to 10 ℃, stirring the reaction liquid I at the temperature of 10 ℃ for 5 hours, heating the temperature of the reaction liquid I to 35 ℃, adding 0.1g of dibutyltin dilaurate into the reaction liquid I at the temperature of 35 ℃, and finally stirring the reaction liquid I at the temperature of 35 ℃ and the stirring speed of 300r/min for 10 hours to obtain a reaction liquid II;
fifthly, adding the reaction liquid II obtained in the first step to 500mL of deionized water to precipitate, standing for 25min, and centrifuging at the centrifugal speed of 7000r/min to obtain a solid reaction product;
sixthly, washing the solid reaction product for 5 times by using deionized water, then putting the solid reaction product washed by the deionized water into a freeze dryer, and freeze-drying for 36 hours at the temperature of minus 10 ℃ to obtain a dry white solid substance, namely the hydroxyl-terminated hyperbranched polymer;
secondly, extraction treatment of carbon fibers:
putting carbon fibers into a Soxhlet extractor filled with acetone, heating the acetone to 82 ℃, continuously evaporating the acetone, condensing the acetone in the Soxhlet extractor, continuously cleaning impurities on the surfaces of the carbon fibers in the distilled acetone for 48 hours, and taking out the carbon fibers to obtain the carbon fibers with the impurities on the surfaces removed; taking out the carbon fiber with the surface impurities removed, and then placing the carbon fiber in an oven with the temperature of 80 ℃ for drying for 2 hours to obtain the carbon fiber after extraction treatment;
thirdly, oxidation:
soaking the extracted carbon fiber into a potassium persulfate/silver nitrate mixed water solution, heating to 60 ℃, and keeping the temperature at 60 ℃ for 2 hours to obtain oxidized carbon fiber; the concentration of potassium persulfate in the potassium persulfate/silver nitrate mixed water solution is 0.2 mol/L; the concentration of silver nitrate in the potassium persulfate/silver nitrate mixed water solution is 0.005 mol/L;
the volume ratio of the mass of the carbon fiber after extraction treatment to the potassium persulfate/silver nitrate mixed water solution in the third step is 1.5g to 300 mL;
soaking the oxidized carbon fibers obtained in the third step in distilled water for 5min at room temperature, taking out the carbon fibers soaked in the distilled water, and removing the distilled water;
the volume ratio of the mass of the oxidized carbon fiber to the distilled water in the third step is 1.5g:500 mL;
thirdly, repeating the third step and the second step for 3 times to obtain oxidized carbon fibers cleaned by distilled water;
fourthly, drying the oxidized carbon fiber cleaned by the distilled water obtained in the third step for 2 hours at the temperature of 80 ℃ to obtain the dried oxidized carbon fiber;
fifthly, placing the dried oxidized carbon fiber obtained in the third step in a Soxhlet extractor filled with absolute ethyl alcohol, and cleaning the oxidized carbon fiber with the absolute ethyl alcohol at the temperature of 90 ℃ for 2 hours to obtain the oxidized carbon fiber cleaned with the absolute ethyl alcohol;
sixthly, drying the oxidized carbon fiber washed by the absolute ethyl alcohol obtained in the third fifth step for 2 hours at the temperature of 80 ℃ to obtain dried oxidized carbon fiber;
fourthly, grafting:
adding 1g of hydroxyl-terminated hyperbranched polymer into 30mL of N, N-dimethylacetamide, performing ultrasound for 30min at the ultrasonic power of 343W, adding 1.5g of dried oxidized carbon fiber, 0.5g of 1-ethyl- (3-dimethylaminopropyl) carbonyldiimine hydrochloride and 0.05g of 4-dimethylaminopyridine, and finally stirring and refluxing for 12h at the temperature of 150 ℃ and the stirring speed of 400r/min to obtain the treated carbon fiber;
secondly, taking out the treated carbon fibers and then immersing the carbon fibers into distilled water for 10 min;
thirdly, the step IV is circulated for 4 times to obtain the treated carbon fiber cleaned by the distilled water;
putting the treated carbon fiber cleaned by the distilled water into a Soxhlet extractor filled with absolute ethyl alcohol, and cleaning the treated carbon fiber cleaned by the distilled water by using the absolute ethyl alcohol at the temperature of 90 ℃ for 2 hours to obtain the treated carbon fiber cleaned by the absolute ethyl alcohol;
and fifthly, drying the treated carbon fiber cleaned by the absolute ethyl alcohol in an oven at the temperature of 80 ℃ for 4 hours to obtain the carbon fiber with the surface grafted with the hydroxyl-terminated hyperbranched polymer, which is expressed as CF-HTHBP.
The experimental results of example two are as follows:
element change before and after carbon fiber modification: compared with CF, the oxygen content of the CF-HTHBP on the surface of the material is increased to 14.36 percent, and the original oxygen element/carbon element ratio is changed from 0.034 to 0.18.
The microscopic morphology changes before and after the carbon fiber modification: the oxidized fiber has more surface defects and damages the strength of the fiber body.
Contact angle and surface energy before and after carbon fiber modification: the contact angle in water and diiodomethane is large, resulting in poor wettability of the carbon fiber with the resin.
Analyzing the interface shear strength and the interlayer shear strength of the carbon fiber: the interfacial shear strength (IFSS) is improved to 60.9MPa from 48.8MPa of the protofilament, and is improved by 25 percent. The interlaminar shear strength (ILSS) is improved from 58.6MPa of the protofilament to 69.7MPa by 19 percent.
As can be seen from the analysis, the effect of the first embodiment is better.

Claims (10)

1. A method for grafting hydroxyl-terminated hyperbranched polymer on the surface of carbon fiber is characterized by comprising the following steps:
firstly, preparing hydroxyl-terminated hyperbranched polymer:
adding isophorone diisocyanate and N, N-dimethylacetamide into a glass container to obtain an isophorone diisocyanate solution; then placing the glass container filled with the isophorone diisocyanate solution in an ice water bath at 0-5 ℃;
the volume ratio of the mass of the isophorone diisocyanate to the volume of the N, N-dimethyl acetamide in the first step (6 g-12 g) is 50 mL;
adding the tris into N, N-dimethylacetamide, and then carrying out ultrasonic mixing for 10-20 min to obtain tris solution;
the volume ratio of the mass of the trihydroxymethyl aminomethane to the volume of the N, N-dimethylacetamide in the step one is (3 g-6 g) to 50 mL;
thirdly, stirring the isophorone diisocyanate solution in the glass container of the ice water bath at the temperature of 0-5 ℃ in the first step at the stirring speed of 300-400 r/min, and then dripping the tris (hydroxymethyl) aminomethane solution into the isophorone diisocyanate solution at the temperature of 0-5 ℃ at the dripping speed of 10-15 drops/min at the stirring speed of 300-400 r/min to obtain a reaction solution I;
the volume ratio of the isophorone diisocyanate solution to the tris solution in the first step is 1: 1;
heating the temperature of the reaction liquid I to 5-10 ℃, stirring and reacting for 5-6 h at the temperature of 5-10 ℃, heating the temperature of the reaction liquid I to 35-40 ℃, adding dibutyltin dilaurate into the reaction liquid I at the temperature of 35-40 ℃, and stirring and reacting for 10-15 h at the temperature of 35-40 ℃ and the stirring speed of 300-400 r/min to obtain a reaction liquid II;
the volume ratio of the mass of the dibutyltin dilaurate to the reaction liquid I in the first step (0.08 g-0.12 g) is 100 mL;
fifthly, adding the reaction liquid II into deionized water to precipitate, standing for 25-30 min, and centrifuging at the centrifugal speed of 6000-8000 r/min to obtain a solid reaction product;
sixthly, washing the solid reaction product for 3 to 5 times by using deionized water, then putting the solid reaction product washed by the deionized water into a freeze dryer, and freeze-drying for 36 to 48 hours at the temperature of minus 10 to minus 5 ℃ to obtain a dry white solid substance, namely the hydroxyl-terminated hyperbranched polymer;
secondly, extraction treatment of carbon fibers:
putting carbon fibers into a Soxhlet extractor filled with acetone, heating the acetone to 75-85 ℃, continuously evaporating the acetone and condensing in the Soxhlet extractor to continuously wash impurities on the surfaces of the carbon fibers in the distilled acetone for 48-72 hours, and taking out the carbon fibers to obtain the carbon fibers with the impurities on the surfaces removed; taking out the carbon fiber with the surface impurities removed, and then placing the carbon fiber in a drying oven at the temperature of 70-80 ℃ for drying for 2-4 h to obtain the carbon fiber after extraction treatment;
thirdly, oxidation:
soaking the extracted carbon fiber into a potassium persulfate/silver nitrate mixed water solution, heating to 60-80 ℃, and keeping the temperature at 60-80 ℃ for 1-2 hours to obtain oxidized carbon fiber; the concentration of the potassium persulfate in the potassium persulfate/silver nitrate mixed water solution is 0.1-0.2 mol/L; the concentration of silver nitrate in the potassium persulfate/silver nitrate mixed water solution is 0.0001-0.05 mol/L;
the volume ratio of the mass of the carbon fiber after extraction treatment to the potassium persulfate/silver nitrate mixed water solution in the third step is (0.3 g-1.5 g) to (300 mL-500 mL);
soaking the oxidized carbon fiber obtained in the third step in distilled water for 5-10 min at room temperature, taking out the carbon fiber soaked in the distilled water, and removing the distilled water;
the volume ratio of the mass of the oxidized carbon fiber to the distilled water in the third step is (0.3 g-1.5 g): 300 mL-500 mL;
thirdly, repeating the third step and the third step for 3 to 5 times to obtain the oxidized carbon fiber cleaned by the distilled water;
fourthly, drying the oxidized carbon fiber cleaned by the distilled water obtained in the third step for 2 to 4 hours at the temperature of between 70 and 80 ℃ to obtain the dried oxidized carbon fiber;
fifthly, placing the dried oxidized carbon fiber obtained in the third step in a Soxhlet extractor filled with absolute ethyl alcohol, and cleaning the oxidized carbon fiber with the absolute ethyl alcohol at the temperature of 90-100 ℃ for 2-4 h to obtain the oxidized carbon fiber cleaned with the absolute ethyl alcohol;
sixthly, drying the oxidized carbon fiber washed by the absolute ethyl alcohol obtained in the third step for 2-4 hours at the temperature of 70-80 ℃ to obtain dried oxidized carbon fiber;
fourthly, grafting:
adding a hydroxyl-terminated hyperbranched polymer into N, N-dimethylacetamide, performing ultrasonic dispersion for 15-30 min, adding dried oxidized carbon fiber, 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride and 4-dimethylaminopyridine, and finally stirring and refluxing for 12-24 h at the temperature of 100-150 ℃ and the stirring speed of 300-400 r/min to obtain the treated carbon fiber;
the mass ratio of the hydroxyl-terminated hyperbranched polymer to the volume of the N, N-dimethylacetamide in the step IV is (1 g-1.5 g): 30 mL-60 mL;
the mass ratio of the dry oxidized carbon fiber to the volume of the N, N-dimethylacetamide in the step IV is (1.0-2.0 g): (30-60 mL);
the volume ratio of the mass of the 1-ethyl- (3-dimethylaminopropyl) carbonyldiimine hydrochloride to the volume of the N, N-dimethylacetamide in the fourth step is (0.5 g-1.0 g): 30 mL-60 mL;
the mass ratio of the 4-dimethylaminopyridine to the N, N-dimethylacetamide in the fourth step is (0.05-0.1 g): 30-60 mL);
secondly, taking out the treated carbon fiber and then immersing the carbon fiber into distilled water for 10-15 min;
thirdly, the step IV is circulated for 3 to 5 times to obtain the treated carbon fiber cleaned by the distilled water;
putting the treated carbon fiber cleaned by the distilled water into a Soxhlet extractor filled with absolute ethyl alcohol, and cleaning the treated carbon fiber cleaned by the distilled water by using the absolute ethyl alcohol at the temperature of 90-100 ℃ for 2-4 h to obtain the treated carbon fiber cleaned by the absolute ethyl alcohol;
and fifthly, drying the treated carbon fiber cleaned by the absolute ethyl alcohol in an oven at the temperature of 75-80 ℃ for 3-5 h to obtain the carbon fiber with the surface grafted with the hydroxyl terminated hyperbranched polymer.
2. The method for grafting the hydroxyl-terminated hyperbranched polymer on the surface of the carbon fiber according to claim 1, wherein the volume ratio of the mass of the isophorone diisocyanate to the volume of the N, N-dimethylacetamide in the step one (r) is (10 g-12 g):50 mL.
3. The method of claim 1, wherein the ratio of the mass of tris (hydroxymethyl) aminomethane to the volume of N, N-dimethylacetamide in the step one (5 g-6 g) is 50 mL.
4. The method for grafting the hydroxyl-terminated hyperbranched polymer onto the surface of the carbon fiber as claimed in claim 1, wherein the mass ratio of the dibutyltin dilaurate to the reaction solution I in the first step (4) is (0.1 g-0.12 g):100 mL.
5. The method of claim 1, wherein the ratio of the mass of the hydroxyl terminated hyperbranched polymer to the volume of N, N-dimethylacetamide in the fourth step is (1.2 g-1.5 g): 45 mL-60 mL).
6. The method of claim 1, wherein the ultrasonic power in the first step is 343W to 346.5W.
7. The method of claim 1, wherein the ratio of the mass of the dried oxidized carbon fiber to the volume of N, N-dimethylacetamide in the step four is (1.5-2.0 g): (30-60 mL).
8. The method of claim 1, wherein the ratio of the mass of 1-ethyl- (3-dimethylaminopropyl) carbonyldiimine hydrochloride to the volume of N, N-dimethylacetamide in the fourth step (1) is (0.5 g-0.67 g) to (50 mL-60 mL).
9. The method for grafting the hydroxyl-terminated hyperbranched polymer on the surface of the carbon fiber according to claim 1, wherein the ultrasonic power in the fourth step is 343W to 346.5W.
10. The method of claim 1, wherein the ratio of the mass of 4-dimethylaminopyridine to the volume of N, N-dimethylacetamide in the fourth step (i) is (0.05-0.067 g) - (50-60 mL).
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