Method for preparing carbon fibers by carbonizing polyacrylonitrile precursors

Abstract

The invention provides a method for preparing carbon fibers by carbonizing polyacrylonitrile precursors. The method comprises the following steps: 1, pre-oxidizing in multiple temperature zones at the temperature of 160-310 DEGC for 60-120 minutes with the draft degree of 0.5-10 percent; 2, carbonizing in multiple temperature zones at low temperature of 400-1000 DEG C for 60-120 seconds with the total draft degree of 1-8 percent; and 3, carbonizing in multiple temperature zones at high temperature of 800-1600 DEG C for 60-120 seconds with the draft degree of negative 8 percent-negative 1 percent. According to the method, the temperature gradient, temperature range, draft ratio, wire traveling speed and other parameters in each stage of the carbonizing process are reasonably designed, so that the pre-oxidizing and carbonizing processes can be performed smoothly, and pre-oxidized fibers have good heat resistance, high molecular orientation degree and compact molecular distribution, uniform carbon fiber structure and few broken and paralleled fibers, and have a tensile strength of over 5000MPA, so that the aim of improving carbon fiber product quality can be achieved.

Description

technical field [0001] The invention belongs to the technical field of carbon fiber material manufacturing, and in particular relates to a carbonization method of carbon fiber precursors. Background technique [0002] Polyacrylonitrile (PAN)-based carbon fiber is a kind of inorganic fiber material with a turbostratic graphite structure with a carbon content of more than 95% and a carbon content of more than 95%, which uses PAN precursor as a precursor and is processed at a high temperature above 1500 ° C. It has high specific strength, A series of excellent properties such as high specific modulus, high temperature resistance, corrosion resistance, fatigue resistance, radiation resistance, electrical conductivity, heat transfer, shock absorption, noise reduction and low relative density. [0003] The preparation of carbon fibers by high-temperature carbonization of PAN precursors needs to go through three stages, pre-oxidation stage, low-temperature carbonization stage and h...

AI Technical Summary

Problems solved by technology

The large temperature difference causes the cyclization reaction to be subject to a large temperature shock, which makes the ring formation speed, oxidation speed, oxygen infiltration speed and the structural change speed of the PAN precursor mismatch, resulting in more structural defects. Broken wires and cross-linked wires seriously affect the quality of the final carbon fiber

[0005] In addition, excessive temperature gradients in the low-temperature carbonization stage and high-temperature carbonization stage also have a greater impact on the quality of carbon fibers. The main reason is that large temperature gradients lead to faster decomposition speeds, and the rapid overflow of small molecular gases generated by decomposition leads to increased carbon fiber structural defects. reduce its tensile strength

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