What are the carbon fiber coating methods?
There are many treatment methods for the surface coating of carbon fibers, such as gas phase precipitation, surface electropolymerization, and coating of polymers. Vapor deposition refers to the deposition of a compound coating on the surface of carbon fibers according to actual needs by utilizing the physical and chemical processes occurring on the surface of carbon fibers in a gas phase environment. Electropolymerization refers to the polymerization of a monomer having a reactive group under the initiation of an electric field. The reaction forms a polymer coating on the surface of the carbon fiber to introduce a part of the reactive functional group of the monomer to the surface of the carbon fiber, thereby improving the interfacial adhesion property of the composite; coating the polymer means sizing after the surface treatment of the carbon fiber. The above various carbon fiber coating treatment methods require severe experimental conditions, and the experimental operation is difficult, and the required equipment requirements are high.
The carbon fiber surface coating treatment method is specifically carried out according to the following steps:
Step 1, fiber pretreatment: firstly, the carbon fiber is subjected to surface degumming treatment by a burning method; then the carbon fiber after surface degumming is roughened by using a nitric acid solution or a sodium hydroxide solution; the carbon fiber after the roughening treatment is placed The activation treatment is carried out in the acetic acid solution to obtain the pretreated carbon fiber;
Step 2: Configuring the sol solution: mixing tetraethyl orthosilicate, carbon fiber with a co-solvent, water and carbon fiber with a catalyst, the amount of which is 1 to 2 mol/L of ethyl orthosilicate, 2 to 3 mol/L of cosolvent, water 10 ～15 mol/L, catalyst 0.1-0.5 mol/L, adjust the pH of the sol solution, stir evenly and then let stand;
Step 3, sol-gel coating treatment: The pretreated carbon fiber obtained in the step 1 is immersed in the sol solution obtained in the step 2, heat-insulated, and shaken to finally obtain a carbon fiber having a surface coated with a dense SiO2 coating.
The invention is also characterized in that
Step 1 is specifically implemented as follows:
Step 1.1, surface degumming: carbon fiber is subjected to high temperature burning, the burning temperature is 450 to 500 ° C, and the time is 30 to 50 min;
Step 1.2, roughening treatment: the carbon fiber removed by the step 1.1 is immersed in a concentration of 15-30% by weight of a nitric acid solution or a concentration of 15-30% by weight of sodium hydroxide solution, boiling time of 40 ~ 60 min;
Step 1.3, activation treatment: the carbon fiber coarsened in step 1.2 is immersed in an acetic acid solution having a concentration of 5-8 mol/L, and left for 5 to 10 minutes to obtain a pretreated carbon fiber;
In step 2, the pH of the sol solution is 2-8, the stirring is uniform, and the standing time is 60-100 min.
In step 3, the oscillation is performed by an ultrasonic oscillator, and the time is 30 to 50 minutes, and the temperature of the water bath is 50 to 80 °C.
The cosolvent in step 2 is ethanol, methanol or acetone.
In step 2, the catalyst is hydrofluoric acid or hydrochloric acid.
The pH of the solution is adjusted in step 2 using ammonia water, lactic acid or a mixture of the two in any ratio.
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