Method for preparing polyimide fiber by combining three-step method and imidization

Abstract

The invention relates to a method for preparing polyimide fiber by combining a three-step method and imidization. The method comprises the following steps: a dianhydride monomer and a diamines monomer are subjected to a condensation polymerization reaction in a reaction solvent to obtain a polyamide acid spinning solution; according to a wet spinning technology, the spinning solution is extruded through a spinning head and is subjected to coagulation bath, washing, and drying to obtain the polyamide acid fiber; then primary heat treatment is carried out to obtain partially imidized fiber; fiber is infiltrated in an acetic anhydride / pyridine solution for chemical imidization; and finally, steps of drying and further thermal cyclization are carried out to obtain the polyimide fiber. According to the invention, the chemical imidization process is added in a traditional thermal imidization process, imidization degree of the fiber is increased, at the same time, a ring-closure reaction in a tubular furnace is reduced by the chemical imidization, draw ratio is increased, fiber orientation degree is increased, so that the mechanical properties of the polyimide fiber are greatly increased.

Description

technical field [0001] The invention belongs to the technical field of materials, and in particular relates to a method for preparing polyimide fibers through three-step mixed imidization. Background technique [0002] Polyimide is a polymer material with excellent chemical stability. It has good mechanical properties and heat resistance, outstanding dielectric properties and radiation resistance, and is widely used in aviation, aerospace, microelectronics, and separation membranes. Key materials in various fields such as lasers and lasers. [0003] However, with the development of science and technology, higher and more stringent requirements are put forward for materials in actual use and application. How to improve the mechanical properties of fibers has attracted widespread attention. [0004] At present, polyimide (PI) fibers are mainly obtained by polyamic acid (PAA) wet spinning and thermal cyclization to obtain polyimide fibers. However, due to the heat treatment p...

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Problems solved by technology

[0005] In addition, in the traditional polyamic acid (PAA) wet spinning process, in the prior art, chemical imidization agents are mostly added to the polyamic acid spinning solution, and then thermal imidization is performed to obtain polyimide fibers. , but because polyimide is insoluble in most organic solvents such as DMAc, DMF, NMP, etc., the amount of chemical imidization reagents is less, and the degree of imidization of polyimide fibers is relatively low, so the mechanical properties are also low. poor

Another existing technology is thermal imidization first, and then chemical imidization to obtain polyimide fibers, but since the chemical imidization process in this method will remove small molecule water, resulting in fiber surface defects, the same will degrade the fiber performance

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