A method for surface modification of carbon fibers

Abstract

The invention relates to a method for modifying surface of carbon fiber. According to the invention, carbon fiber with the surface coated with a thermosetting resin sizing agent is subjected to low-temperature heat treatment, the surface coated with the thermosetting resin sizing agent of the carbon fiber contains a carboxyl group, the ratio of the carboxyl group to the surface C-C bond is 2-30%,the low temperature heat treatment is characterized in that insulation is carried out at the temperature of 250-350 DEG C for 0.5-15 min, the low temperature heat treatment is carried out under oxidizing atmosphere, the oxidizing atmosphere is mixed gas environment of oxidizing gas environment or oxidizing gas and inert gas, and the volume ratio of oxidizing gas in the mixed gas environment is greater than or equal to 5%. The modification method has the advantages of low heat treatment temperature, small energy consumption, and good processing effect, the processed surface obtains the carboxylgroup capable of reacting with a thermoplastic resin matrix, is in favor of chemical bonding of carbon fiber and the thermoplastic resin matrix, greatly increases the interface performance of carbonfiber and a thermoplastic matrix, and has application prospect.

Description

technical field [0001] The invention belongs to the field of carbon fiber modification and relates to a method for modifying the surface of carbon fiber. Background technique [0002] Because carbon fiber reinforced thermoplastic resin (CFRTP)-based composites have the advantages of fast molding, recyclability, easy repair, low cost, excellent ultimate fatigue resistance and simple storage conditions for prepregs, they are widely used in aerospace, automotive and sports and leisure fields. has been widely used. The rapid development of high-performance thermoplastic resins in recent years has also accelerated the development of CFRTP-based composites. [0003] Compared with carbon fiber reinforced thermosetting resin composite materials, the market share of CFRTP-based composite materials is still quite low, mainly because the carbon fiber raw materials used in thermoplastic resin composite materials are relatively limited. At present, most carbon fiber reinforced thermose...

AI Technical Summary

Problems solved by technology

[0004] (1) Carbon fiber has poor or incompatible compatibility with most thermoplastic resins

Epoxy resin sizing agents do not chemically react with these thermoplastic polymers, resulting in low interlaminar shear strength of their composites;

[0005] (2) The molding temperature of the thermosetting epoxy resin sizing agent is lower than 250°C. If the temperature exceeds 250°C, the epoxy resin sizing agent will degrade and generate gas, forming tiny micropores on the surface of the composite material, resulting in the failure of composite material molding;

[0006] (3) After the carbon fiber coated with epoxy resin sizing agent is reinforced with thermoplastic resin and used at high temperature for a long time, the interface often produces voids and delamination, resulting in a serious decline in the interface performance of the composite material

However, the ozone oxidation reaction is relatively severe, which seriously damages the carbon fiber itself, resulting in a decrease in the tensile strength of the carbon fiber itself, and secondly, the stability is difficult to control, the repeatability is relatively poor, and the operating flexibility is narrow.

[0013] In addition, there are a large number of hydroxyl groups and methylene groups on the surface of carbon fibers coated with thermosetting epoxy resin sizing agents, and the processing temperature of thermoplastic resins is higher than 250 ° C. If the carbon fibers are directly processed with thermoplastic resins, the surface of carbon fibers will not Stable groups and carbon chains will decompose to generate a large amount of gas, resulting in greatly reduced interfacial adhesion

Images