阅读说明：本技术 一种高强度的纤维素接枝聚丙烯腈复合纤维的制法与应用 (Preparation method and application of high-strength cellulose grafted polyacrylonitrile composite fiber ) 是由 李宇凡 于 2021-01-08 设计创作，主要内容包括：本发明涉及复合纤维技术领域,且公开了一种高强度的纤维素接枝聚丙烯腈复合纤维,纤维素纳米晶接枝聚丙烯腈,通过化学键的连接,将纤维素纳米晶与聚丙烯腈有机结合,化学键的键能远大于纤维素纳米晶和聚丙烯腈之间的分子间作用力,从而提高了两者之间的相容性和界面亲和性,避免了两者发生相分离和脱落的现象,进一步通过静电纺丝过程,得到纤维素接枝聚丙烯腈复合纤维,刚性的纤维素纳米晶对复合纤维的弹性模量和拉伸强度具有良好的提升作用,同时复合纤维含有大量的疏水性长烷基链,使复合纤维具有良好的疏水性,拓展了聚丙烯腈复合纤维在超疏水和自清洁抗污领域中的应用。(The invention relates to the technical field of composite fibers, and discloses a high-strength cellulose grafted polyacrylonitrile composite fiber, cellulose nanocrystalline grafted polyacrylonitrile, the cellulose nanocrystalline and the polyacrylonitrile are organically combined through the connection of chemical bonds, the bond energy of the chemical bonds is far larger than the intermolecular force between the cellulose nanocrystalline and the polyacrylonitrile, thereby improving the compatibility and the interface affinity between the cellulose and the polyacrylonitrile, avoiding the phenomenon of phase separation and shedding of the cellulose and the polyacrylonitrile, further obtaining the cellulose grafted polyacrylonitrile composite fiber through the electrostatic spinning process, wherein the rigid cellulose nanocrystal has good promotion effect on the elastic modulus and the tensile strength of the composite fiber, meanwhile, the composite fiber contains a large number of hydrophobic long alkyl chains, so that the composite fiber has good hydrophobicity, and the application of the polyacrylonitrile composite fiber in the fields of super hydrophobicity, self-cleaning and stain resistance is expanded.)

1. A high-strength cellulose grafted polyacrylonitrile composite fiber is characterized in that: the preparation method of the high-strength cellulose grafted polyacrylonitrile composite fiber comprises the following steps:

(1) adding cellulose nanocrystals into ethanol, performing ultrasonic dispersion until the cellulose nanocrystals are uniform, adding stearic acid, and performing long-chain alkylation hydrophobic modification reaction to obtain stearic acid modified cellulose nanocrystals;

(2) adding stearic acid modified cellulose nanocrystal into N, N-dimethylformamide, stirring uniformly, placing in an ice water bath for cooling, adding 2-bromoisobutyryl bromide and 4-dimethylaminopyridine, carrying out a bromoisobutyryl esterification reaction, and washing with ethanol and distilled water to obtain bromoisobutyl ester-alkylated modified cellulose nanocrystal;

(3) adding isobutyl bromide-alkylated modified cellulose nanocrystal, acrylonitrile, 1,4,7,10, 10-hexamethyltriethylenetetramine and 2-methyl bromoisobutyrate into a mixed solvent of N, N-dimethylformamide and tetrahydrofuran, uniformly stirring, performing freezing treatment, vacuumizing and nitrogen filling treatment, adding cuprous bromide in a nitrogen atmosphere, and performing polymerization reaction to obtain cellulose grafted polyacrylonitrile;

(4) placing the cellulose grafted polyacrylonitrile in N, N-dimethylformamide, stirring for 10-20h, precipitating spinning solution, and injecting into an injector to perform electrostatic spinning process to obtain the high-strength cellulose grafted polyacrylonitrile composite fiber.

2. The high strength cellulose grafted polyacrylonitrile composite fiber according to claim 1, wherein: the mass ratio of the cellulose nanocrystals to the stearic acid in the step (1) is 100: 50-120.

3. The high strength cellulose grafted polyacrylonitrile composite fiber according to claim 1, wherein: the reaction temperature of the long-chain alkylation hydrophobic modification reaction in the step (1) is 60-80 ℃, and the reaction time is 6-12 h.

4. The high strength cellulose grafted polyacrylonitrile composite fiber according to claim 1, wherein: the mass ratio of the stearic acid modified cellulose nanocrystal, the 2-bromoisobutyryl bromide and the 4-dimethylaminopyridine in the step (2) is 100:5-25: 3-12.

5. The high strength cellulose grafted polyacrylonitrile composite fiber according to claim 1, wherein: the reaction temperature of the bromine isobutyl esterification reaction in the step (3) is 25-45 ℃, and the reaction time is 20-30 h.

6. The high strength cellulose grafted polyacrylonitrile composite fiber according to claim 1, wherein: the mass ratio of the isobutyl bromide-alkylated modified cellulose nanocrystal, the acrylonitrile, the 1,1,4,7,10, 10-hexamethyltriethylenetetramine, the methyl 2-bromoisobutyrate and the cuprous bromide in the step (3) is 5-30:100:0.8-5:0.3-1.5: 0.5-3.

7. The high strength cellulose grafted polyacrylonitrile composite fiber according to claim 1, wherein: the temperature of the polymerization reaction in the step (3) is 70-90 ℃, and the reaction time is 20-40 h.

8. The high strength cellulose grafted polyacrylonitrile composite fiber according to claim 1, wherein: the spinning voltage of the electrostatic spinning process in the step (4) is 18-22kV, the spinning flow rate is 0.5-1.5mL/h, and the receiving distance between the needle head of the spinning injector and the receiving plate is 15-25 cm.

Technical Field

The invention relates to the technical field of composite fibers, in particular to a preparation method and application of a high-strength cellulose grafted polyacrylonitrile composite fiber.

Background

Polyacrylonitrile fiber, commonly known as acrylic fiber, is fiber or copolymer fiber spun by polyacrylonitrile, has good weather resistance and sun resistance, and has good bulkiness, elasticity and heat retention, so polyacrylonitrile fiber wool fabric or wool fabric blended with wool is made into fabrics such as blankets, carpets and the like, and has wide application in outdoor fabrics such as sails, military canvases, tents and the like, but the traditional polyacrylonitrile fiber has low strength and poor toughness, and limits further application and development of the polyacrylonitrile fiber.

Cellulose is a natural polymer which is most widely distributed in nature and most abundant in reserves, cellulose molecules have polarity and have very strong rigidity and mechanical strength, so that the cellulose and polyacrylonitrile can be organically combined to obtain the composite fiber, the mechanical strength and practical application of the polyacrylonitrile are improved, but the polyacrylonitrile contains a strong polar group and has strong intermolecular force with a molecular chain of the polar cellulose, so that the cellulose and the polyacrylonitrile are easy to separate, pores and cracks are easy to generate in the composite fiber, the comprehensive performance of the composite fiber is reduced, and meanwhile, the cellulose contains a large number of hydrophilic hydroxyl groups, and after being compounded with the polyacrylonitrile, the application of the composite fiber in the aspects of superhydrophobicity, self-cleaning, stain resistance and the like can be limited.

Technical problem to be solved

Aiming at the defects of the prior art, the invention provides a preparation method and application of a high-strength cellulose grafted polyacrylonitrile composite fiber, which has higher mechanical strength and hydrophobic property.

(II) technical scheme

In order to achieve the purpose, the invention provides the following technical scheme: a preparation method of high-strength cellulose grafted polyacrylonitrile composite fiber comprises the following steps:

(1) adding cellulose nanocrystalline into ethanol, performing ultrasonic dispersion until the cellulose nanocrystalline is uniform, adding stearic acid, performing long-chain alkylation hydrophobic modification reaction, removing the solvent through reduced pressure distillation, and washing the ethanol and distilled water to obtain stearic acid modified cellulose nanocrystalline.

(2) Adding stearic acid modified cellulose nanocrystalline into N, N-dimethylformamide, stirring, cooling in ice water bath, adding 2-bromoisobutyryl bromide and 4-dimethylaminopyridine, performing bromoisobutyration reaction, and adding saturated NaHCO₃Precipitating the solution, filtering to remove the solvent, and washing with ethanol and distilled water to obtain the isobutyl bromide-alkylated modified cellulose nanocrystal.

(3) Adding isobutyl bromide-alkylated modified cellulose nanocrystal, acrylonitrile, 1,4,7,10, 10-hexamethyltriethylenetetramine and 2-methyl bromoisobutyrate into a mixed solvent of N, N-dimethylformamide and tetrahydrofuran, uniformly stirring, performing freezing treatment, vacuumizing and nitrogen filling treatment, adding cuprous bromide in a nitrogen atmosphere for polymerization, adding methanol for precipitation, filtering to remove the solvent, and washing with ethanol and distilled water to obtain the cellulose grafted polyacrylonitrile.

(4) Placing the cellulose grafted polyacrylonitrile in N, N-dimethylformamide, stirring for 10-20h, precipitating spinning solution, and injecting into an injector to perform electrostatic spinning process to obtain the high-strength cellulose grafted polyacrylonitrile composite fiber.

Preferably, the mass ratio of the cellulose nanocrystals to the stearic acid in the step (1) is 100: 50-120.

Preferably, the reaction temperature of the long-chain alkylation hydrophobic modification reaction in the step (1) is 60-80 ℃, and the reaction time is 6-12 h.

Preferably, the mass ratio of the stearic acid modified cellulose nanocrystal, the 2-bromoisobutyryl bromide and the 4-dimethylaminopyridine in the step (2) is 100:5-25: 3-12.

Preferably, the reaction temperature of the bromine isobutyl esterification reaction in the step (3) is 25-45 ℃, and the reaction time is 20-30 h.

Preferably, the mass ratio of the isobutyl bromide-alkylated modified cellulose nanocrystal, the acrylonitrile, the 1,1,4,7,10, 10-hexamethyltriethylenetetramine, the methyl 2-bromoisobutyrate and the cuprous bromide in the step (3) is 5-30:100:0.8-5:0.3-1.5: 0.5-3.

Preferably, the temperature of the polymerization reaction in the step (3) is 70-90 ℃, and the reaction time is 20-40 h.

Preferably, the spinning voltage of the electrostatic spinning process in the step (4) is 18-22kV, the spinning flow rate is 0.5-1.5mL/h, and the receiving distance between the needle of the spinning injector and the receiving plate is 15-25 cm.

(III) advantageous technical effects

Compared with the prior art, the invention has the following chemical mechanism and beneficial technical effects:

according to the high-strength cellulose grafted polyacrylonitrile composite fiber, the carboxyl of stearic acid reacts with part of the hydroxyl of the cellulose nanocrystal to obtain stearic acid modified cellulose nanocrystal, so that long-chain alkylated hydrophobic modification of cellulose is realized, and the application of the cellulose nanocrystal in the aspects of superhydrophobicity, self-cleaning, stain resistance and the like is expanded.

The high-strength cellulose grafted polyacrylonitrile composite fiber is characterized in that under the catalytic action of 4-dimethylamino pyridine, 2-bromoisobutyryl bromide and stearic acid modified cellulose nanocrystals are subjected to esterification reaction to obtain isobutyl bromide-alkylated modified cellulose nanocrystals, the isobutyl bromide-alkylated modified cellulose nanocrystals are used as an ATRP macromolecular initiator, isobutyl bromide groups are used as a chemical initiation center to initiate acrylonitrile and the cellulose nanocrystals to undergo atom transfer radical polymerization to obtain cellulose nanocrystal grafted polyacrylonitrile, the cellulose nanocrystals and polyacrylonitrile are organically combined through the connection of chemical bonds, and the bonds of the chemical bonds are far greater than the intermolecular forces between the cellulose nanocrystals and the polyacrylonitrile, so that the compatibility and the interfacial affinity between the cellulose nanocrystals are improved, the phenomena of phase separation and shedding of the cellulose nanocrystals are avoided, and the electrostatic spinning process is further carried out, the obtained cellulose grafted polyacrylonitrile composite fiber has the advantages that the rigid cellulose nanocrystals have good lifting effects on the elastic modulus and tensile strength of the composite fiber, and meanwhile, the composite fiber contains a large number of hydrophobic long alkyl chains, so that the composite fiber has good hydrophobicity, and the application of the polyacrylonitrile composite fiber in the fields of superhydrophobicity and anti-fouling self-cleaning is expanded.

Detailed Description

To achieve the above object, the present invention provides the following embodiments and examples: a high-strength cellulose grafted polyacrylonitrile composite fiber is prepared by the following steps:

(1) adding cellulose nanocrystals into ethanol, performing ultrasonic dispersion until the cellulose nanocrystals are uniform, adding stearic acid, controlling the mass ratio of the cellulose nanocrystals to the stearic acid to be 100:50-120, performing long-chain alkylation hydrophobic modification reaction at the reaction temperature of 60-80 ℃ for 6-12h, removing the solvent by reduced pressure distillation, and washing the ethanol and distilled water to obtain the stearic acid modified cellulose nanocrystals.

(2) Adding stearic acid modified cellulose nanocrystal into N, N-dimethylformamide, stirring uniformly, placing in ice water bath for cooling, adding 2-bromine isobutyryl bromide and 4-dimethylaminopyridine, controlling the mass ratio of stearic acid modified cellulose nanocrystal, 2-bromine isobutyryl bromide and 4-dimethylaminopyridine to be 100:5-25:3-12, carrying out bromine isobutyl esterification reaction at the reaction temperature of 25-45 ℃ for 20-30h, adding saturated NaHCO₃Precipitating the solution, filtering to remove the solvent, and washing with ethanol and distilled water to obtain the isobutyl bromide-alkylated modified cellulose nanocrystal.

(3) Adding isobutyl bromide-alkylated modified cellulose nanocrystal, acrylonitrile, 1,4,7,10, 10-hexamethyltriethylenetetramine and 2-methyl bromoisobutyrate into a mixed solvent of N, N-dimethylformamide and tetrahydrofuran, uniformly stirring, then performing freezing treatment, vacuumizing and nitrogen filling treatment, adding cuprous bromide into a nitrogen atmosphere, wherein the mass ratio of the isobutyl bromide-alkylated modified cellulose nanocrystal, the acrylonitrile, the 1,1,4,7,10, 10-hexamethyltriethylenetetramine, the 2-methyl bromoisobutyrate to the cuprous bromide is 5-30:100:0.8-5:0.3-1.5:0.5-3, performing polymerization at the temperature of 70-90 ℃ for 20-40h, then adding methanol for precipitation, filtering to remove the solvent, washing with ethanol and distilled water, and obtaining the cellulose grafted polyacrylonitrile.

(4) Placing the cellulose grafted polyacrylonitrile in N, N-dimethylformamide, stirring for 10-20h, precipitating spinning solution, injecting into an injector for electrostatic spinning process, wherein the spinning voltage is 18-22kV, the spinning flow rate is 0.5-1.5mL/h, and the receiving distance between the needle head of the spinning injector and a receiving plate is 15-25cm, thus obtaining the high-strength cellulose grafted polyacrylonitrile composite fiber.

Example 1

(1) Adding cellulose nanocrystals into ethanol, performing ultrasonic dispersion until the cellulose nanocrystals are uniform, adding stearic acid, controlling the mass ratio of the cellulose nanocrystals to the stearic acid to be 100:50, performing long-chain alkylation hydrophobic modification reaction at the reaction temperature of 60 ℃ for 6 hours, performing reduced pressure distillation to remove the solvent, and washing the ethanol and distilled water to obtain the stearic acid modified cellulose nanocrystals.

(2) Adding stearic acid modified cellulose nanocrystal into N, N-dimethylformamide, stirring uniformly, placing in ice water bath for cooling, adding 2-bromoisobutyryl bromide and 4-dimethylaminopyridine, controlling the mass ratio of stearic acid modified cellulose nanocrystal to 2-bromoisobutyryl bromide to 4-dimethylaminopyridine to be 100:5:3, carrying out bromine isobutyl esterification reaction at the reaction temperature of 25 ℃ for 20h, and adding saturated NaHCO₃Precipitating the solution, filtering to remove the solvent, and washing with ethanol and distilled water to obtain the isobutyl bromide-alkylated modified cellulose nanocrystal.

(3) Adding isobutyl bromide-alkylated modified cellulose nanocrystal, acrylonitrile, 1,4,7,10, 10-hexamethyltriethylenetetramine and 2-methyl bromoisobutyrate into a mixed solvent of N, N-dimethylformamide and tetrahydrofuran, uniformly stirring, performing freezing treatment, vacuumizing and nitrogen filling treatment, adding cuprous bromide in a nitrogen atmosphere, wherein the mass ratio of the isobutyl bromide-alkylated modified cellulose nanocrystal to the acrylonitrile to the 1,1,4,7,10, 10-hexamethyltriethylenetetramine to the 2-methyl bromoisobutyrate to the cuprous bromide is 5:100:0.8:0.3:0.5, carrying out polymerization reaction at the temperature of 70 ℃ for 20h, then adding methanol for precipitation, filtering to remove the solvent, and washing with ethanol and distilled water to obtain the cellulose grafted polyacrylonitrile.

(4) Placing the cellulose grafted polyacrylonitrile in N, N-dimethylformamide, stirring for 10h, separating out spinning solution, injecting into an injector for electrostatic spinning, wherein the spinning voltage is 18kV, the spinning flow rate is 0.5mL/h, and the receiving distance between the needle head of the spinning injector and a receiving plate is 15cm, so as to obtain the high-strength cellulose grafted polyacrylonitrile composite fiber.

Example 2

(1) Adding cellulose nanocrystals into ethanol, performing ultrasonic dispersion until the cellulose nanocrystals are uniform, adding stearic acid, controlling the mass ratio of the cellulose nanocrystals to the stearic acid to be 100:70, performing long-chain alkylation hydrophobic modification reaction at the reaction temperature of 70 ℃ for 8 hours, performing reduced pressure distillation to remove the solvent, and washing the ethanol and distilled water to obtain the stearic acid modified cellulose nanocrystals.

(2) Adding into N, N-dimethylformamideAdding stearic acid modified cellulose nanocrystal, stirring uniformly, placing in ice water bath for cooling, adding 2-bromine isobutyryl bromide and 4-dimethylamino pyridine, controlling the mass ratio of stearic acid modified cellulose nanocrystal to 2-bromine isobutyryl bromide to 4-dimethylamino pyridine to be 100:10:5, carrying out bromine isobutyl esterification reaction at 35 ℃ for 24h, adding saturated NaHCO₃Precipitating the solution, filtering to remove the solvent, and washing with ethanol and distilled water to obtain the isobutyl bromide-alkylated modified cellulose nanocrystal.

(3) Adding isobutyl bromide-alkylated modified cellulose nanocrystal, acrylonitrile, 1,4,7,10, 10-hexamethyltriethylenetetramine and 2-methyl bromoisobutyrate into a mixed solvent of N, N-dimethylformamide and tetrahydrofuran, uniformly stirring, performing freezing treatment, vacuumizing and nitrogen filling treatment, adding cuprous bromide in a nitrogen atmosphere, wherein the mass ratio of isobutyl bromide-alkylated modified cellulose nanocrystal, acrylonitrile, 1,4,7,10, 10-hexamethyltriethylenetetramine, 2-methyl bromoisobutyrate and cuprous bromide is 12:100:1.5:0.6:1, polymerization is carried out at the temperature of 80 ℃ for 30h, then adding methanol for precipitation, filtering to remove the solvent, and washing with ethanol and distilled water to obtain the cellulose grafted polyacrylonitrile.

(4) Placing the cellulose grafted polyacrylonitrile in N, N-dimethylformamide, stirring for 20h, separating out spinning solution, injecting into an injector for electrostatic spinning, wherein the spinning voltage is 18kV, the spinning flow rate is 1mL/h, and the receiving distance between the needle head of the spinning injector and a receiving plate is 20cm, so as to obtain the high-strength cellulose grafted polyacrylonitrile composite fiber.

Example 3

(1) Adding cellulose nanocrystals into ethanol, performing ultrasonic dispersion until the cellulose nanocrystals are uniform, adding stearic acid, controlling the mass ratio of the cellulose nanocrystals to the stearic acid to be 1:1, performing long-chain alkylation hydrophobic modification reaction at the reaction temperature of 70 ℃ for 8 hours, performing reduced pressure distillation to remove the solvent, and washing the ethanol and distilled water to obtain the stearic acid modified cellulose nanocrystals.

(2) Adding stearic acid modified cellulose nanocrystalline into N, N-dimethylformamide, stirring uniformly, and placing in iceCooling in water bath, adding 2-bromoisobutyryl bromide and 4-dimethylaminopyridine, controlling the mass ratio of stearic acid modified cellulose nanocrystal to the 2-bromoisobutyryl bromide to the 4-dimethylaminopyridine to be 100:18:8, carrying out bromine isobutyl esterification reaction at 35 ℃ for 24h, and adding saturated NaHCO₃Precipitating the solution, filtering to remove the solvent, and washing with ethanol and distilled water to obtain the isobutyl bromide-alkylated modified cellulose nanocrystal.

(3) Adding isobutyl bromide-alkylated modified cellulose nanocrystal, acrylonitrile, 1,4,7,10, 10-hexamethyltriethylenetetramine and 2-methyl bromoisobutyrate into a mixed solvent of N, N-dimethylformamide and tetrahydrofuran, uniformly stirring, performing freezing treatment, vacuumizing and nitrogen filling treatment, adding cuprous bromide in a nitrogen atmosphere, wherein the mass ratio of isobutyl bromide-alkylated modified cellulose nanocrystal, acrylonitrile, 1,4,7,10, 10-hexamethyltriethylenetetramine, 2-methyl bromoisobutyrate to cuprous bromide is 22:100:3.5:1.2:2, polymerization is carried out at the temperature of 80 ℃ for 30h, then adding methanol for precipitation, filtering to remove the solvent, and washing with ethanol and distilled water to obtain the cellulose grafted polyacrylonitrile.

(4) Placing the cellulose grafted polyacrylonitrile in N, N-dimethylformamide, stirring for 15h, separating out spinning solution, injecting into an injector for electrostatic spinning, wherein the spinning voltage is 20kV, the spinning flow rate is 1mL/h, and the receiving distance between the needle head of the spinning injector and a receiving plate is 20cm, so as to obtain the high-strength cellulose grafted polyacrylonitrile composite fiber.

Example 4

(1) Adding cellulose nanocrystals into ethanol, performing ultrasonic dispersion until the cellulose nanocrystals are uniform, adding stearic acid, controlling the mass ratio of the cellulose nanocrystals to the stearic acid to be 100:120, performing long-chain alkylation hydrophobic modification reaction at the reaction temperature of 80 ℃ for 12 hours, performing reduced pressure distillation to remove the solvent, and washing the ethanol and distilled water to obtain the stearic acid modified cellulose nanocrystals.

(2) Adding stearic acid modified cellulose nanocrystalline into N, N-dimethylformamide, stirring uniformly, placing in ice water bath for cooling, adding 2-bromine isobutyryl bromide and 4-dimethylamino pyridinePyridine, controlling the mass ratio of stearic acid modified cellulose nanocrystal, 2-bromine isobutyryl bromide and 4-dimethylamino pyridine to be 100:25:12, carrying out bromine isobutyl esterification reaction at the reaction temperature of 45 ℃ for 30h, adding saturated NaHCO₃Precipitating the solution, filtering to remove the solvent, and washing with ethanol and distilled water to obtain the isobutyl bromide-alkylated modified cellulose nanocrystal.

(3) Adding isobutyl bromide-alkylated modified cellulose nanocrystal, acrylonitrile, 1,4,7,10, 10-hexamethyltriethylenetetramine and 2-methyl bromoisobutyrate into a mixed solvent of N, N-dimethylformamide and tetrahydrofuran, uniformly stirring, performing freezing treatment, vacuumizing and nitrogen filling treatment, adding cuprous bromide in a nitrogen atmosphere, wherein the mass ratio of isobutyl bromide-alkylated modified cellulose nanocrystal, acrylonitrile, 1,4,7,10, 10-hexamethyltriethylenetetramine, 2-methyl bromoisobutyrate and cuprous bromide is 30:100:5:1.5:3, polymerization is carried out at the temperature of 90 ℃ for 40h, then adding methanol for precipitation, filtering to remove the solvent, and washing with ethanol and distilled water to obtain the cellulose grafted polyacrylonitrile.

(4) Placing the cellulose grafted polyacrylonitrile in N, N-dimethylformamide, stirring for 20h, separating out spinning solution, injecting into an injector for electrostatic spinning, wherein the spinning voltage is 22kV, the spinning flow rate is 1.5mL/h, and the receiving distance between the needle head of the spinning injector and a receiving plate is 25cm, so as to obtain the high-strength cellulose grafted polyacrylonitrile composite fiber.

Comparative example 1

(1) Adding cellulose nanocrystals into ethanol, performing ultrasonic dispersion until the cellulose nanocrystals are uniform, adding stearic acid, controlling the mass ratio of the cellulose nanocrystals to the stearic acid to be 100:35, performing long-chain alkylation hydrophobic modification reaction at the reaction temperature of 70 ℃ for 12 hours, performing reduced pressure distillation to remove the solvent, and washing the ethanol and distilled water to obtain the stearic acid modified cellulose nanocrystals.

(2) Adding stearic acid modified cellulose nanocrystal into N, N-dimethylformamide, stirring, cooling in ice water bath, adding 2-bromoisobutyryl bromide and 4-dimethylaminopyridine, and controlling stearic acid modified cellulose nanocrystal and 2-bromoisobutyrylThe mass ratio of acyl bromide to 4-dimethylamino pyridine is 100:2:1.5, bromine is subjected to isobutyl esterification reaction at the temperature of 35 ℃ for 20h, and saturated NaHCO is added₃Precipitating the solution, filtering to remove the solvent, and washing with ethanol and distilled water to obtain the isobutyl bromide-alkylated modified cellulose nanocrystal.

(3) Adding isobutyl bromide-alkylated modified cellulose nanocrystal, acrylonitrile, 1,4,7,10, 10-hexamethyltriethylenetetramine and 2-methyl bromoisobutyrate into a mixed solvent of N, N-dimethylformamide and tetrahydrofuran, uniformly stirring, performing freezing treatment, vacuumizing and nitrogen filling treatment, adding cuprous bromide in a nitrogen atmosphere, wherein the mass ratio of the isobutyl bromide-alkylated modified cellulose nanocrystal to the acrylonitrile to the 1,1,4,7,10, 10-hexamethyltriethylenetetramine to the 2-methyl bromoisobutyrate to the cuprous bromide is 2:100:0.35:0.15:0.2, carrying out polymerization reaction at the temperature of 80 ℃ for 40h, then adding methanol for precipitation, filtering to remove the solvent, and washing with ethanol and distilled water to obtain the cellulose grafted polyacrylonitrile.

(4) Placing the cellulose grafted polyacrylonitrile in N, N-dimethylformamide, stirring for 20h, separating out spinning solution, injecting into an injector for electrostatic spinning, wherein the spinning voltage is 18kV, the spinning flow rate is 1mL/h, and the receiving distance between the needle head of the spinning injector and a receiving plate is 20cm, so as to obtain the high-strength cellulose grafted polyacrylonitrile composite fiber.

Comparative example 2

(1) Adding cellulose nanocrystals into ethanol, performing ultrasonic dispersion until the cellulose nanocrystals are uniform, adding stearic acid, controlling the mass ratio of the cellulose nanocrystals to the stearic acid to be 100:150, performing long-chain alkylation hydrophobic modification reaction at the reaction temperature of 70 ℃ for 12 hours, performing reduced pressure distillation to remove the solvent, and washing the ethanol and distilled water to obtain the stearic acid modified cellulose nanocrystals.

(2) Adding stearic acid modified cellulose nanocrystalline into N, N-dimethylformamide, stirring uniformly, placing in ice water bath for cooling, adding 2-bromoisobutyryl bromide and 4-dimethylaminopyridine, controlling the mass ratio of stearic acid modified cellulose nanocrystalline, 2-bromoisobutyryl bromide and 4-dimethylaminopyridine to be 100:32:15,performing bromine isobutyl esterification reaction at 30 deg.C for 24 hr, adding saturated NaHCO₃Precipitating the solution, filtering to remove the solvent, and washing with ethanol and distilled water to obtain the isobutyl bromide-alkylated modified cellulose nanocrystal.

(3) Adding isobutyl bromide-alkylated modified cellulose nanocrystal, acrylonitrile, 1,4,7,10, 10-hexamethyltriethylenetetramine and 2-methyl bromoisobutyrate into a mixed solvent of N, N-dimethylformamide and tetrahydrofuran, uniformly stirring, performing freezing treatment, vacuumizing and nitrogen filling treatment, adding cuprous bromide in a nitrogen atmosphere, wherein the mass ratio of the isobutyl bromide-alkylated modified cellulose nanocrystal to the acrylonitrile to the 1,1,4,7,10, 10-hexamethyltriethylenetetramine to the 2-methyl bromoisobutyrate to the cuprous bromide is 38:100:6.5:1.8:4, the polymerization reaction is carried out at the temperature of 80 ℃ for 40h, then adding methanol for precipitation, filtering to remove the solvent, and washing with ethanol and distilled water to obtain the cellulose grafted polyacrylonitrile.

(4) Placing the cellulose grafted polyacrylonitrile in N, N-dimethylformamide, stirring for 20h, separating out spinning solution, injecting into an injector for electrostatic spinning, wherein the spinning voltage is 20kV, the spinning flow rate is 1mL/h, and the receiving distance between the needle head of the spinning injector and a receiving plate is 20cm, so as to obtain the high-strength cellulose grafted polyacrylonitrile composite fiber.

The tensile property of the high-strength cellulose grafted polyacrylonitrile composite fiber is tested by using an WEW-1000 liquid crystal digital display universal tester, GB/T38534-.

And pressing the sdc350 contact angle measuring instrument into a film, and testing the water contact angle of the surface of the film by using the sdc350 contact angle measuring instrument, wherein the test standard is GB/T30693-.

Testing	Example 1	Example 2	Example 3	Example 4	Comparative example 1	Comparative example 2
							Water contact angle	123.5	129.7	142.7	119.7	91.4	80.8