TLCP Fiber Is A New Force In The Field Of Dual-Use Reinforced Materials.

Wang Hua, the chief engineer of Sichuan Textile Science Research Institute, is a high performance industrial fiber made from thermotropic liquid crystalline poly (aryl ester) (TLCP) fiber. It has high strength, high modulus, high temperature resistance, chemical corrosion resistance, and has excellent linear expansion coefficient and aging resistance.

At present, the development of heat treatment process for TLCP nascent fibers is very weak.

TLCP polyaramid fibers are usually prepared by melt spinning.

Because the viscosity of polyaryl ester liquid crystal melt increases sharply with the increase of molecular weight, so the molecular weight of spinning liquid is limited, and the strength of fiber can not meet the requirement. This is the most important problem in melt liquid crystal spinning.

In order to further improve the fiber properties, heat treatment (i.e. solid phase polymerization) is usually used to increase the molecular weight of the aromatic fiber and perfect the fiber crystallization, thereby further improving the fiber strength.

Solid phase during heat treatment

Involving the pesterification of aromatic ester molecular chains and the esterification reaction at the end of molecular chains, the two reactions will produce by-products of small molecules such as water and acetic acid, which will not cause harm to the environment.

The TLCP fiber used in this test is self-assembled twin screw extruder from commercial Vectran liquid crystal polyester chip through the high-performance fiber research laboratory of Sichuan Academy of textile science.

The diameter of the spinneret is 0.30mm, the number of holes is 50, and the average linear density of the fiber is 367.99dtex.

By studying the kinetics of PET and polyamide solid phase condensation, the macrokinetics of post solid polymerization of TLCP fibers was studied with thermotropic liquid crystalline aromatic polyesters as raw materials, and the thermal properties and surface morphology of TLCP fibers before and after heat treatment were studied.

After analysis, it is found that TLCP fibers are widely used in aerospace, armored protection, warship rope and other fields of defense and high temperature filtration materials.

In the heat treatment process, the small molecule by-products produced by solid phase polymerization of TLCP fibers are continuously released, and the quality of TLCP fibers decreases with the change of heat treatment time.

The kinetics of post solid phase polymerization was studied by changing the amount of small molecule by-products produced by TLCP fiber over time.

During the experiment, the thermal history of the fibers at the same temperature was guaranteed to be the same at different temperatures. The weight loss rate was defined as the amount of small molecule by-products produced by TLCP fibers of different unit temperatures at the same temperature.

On the one hand, the increase of heat treatment temperature increases the diffusion rate and activity of the end groups of the aromatic chains, thus accelerating the pesterification and condensation reaction; on the other hand, the diffusion rate of the small molecules of the by-products increases, thus promoting the reaction equilibrium to the positive reaction direction.

The influence of heat treatment temperature on the solid phase condensation is much more obvious than that of the time. Therefore, in the post production process of TLCP fiber, the heat treatment temperature should be raised as far as possible when avoiding adhesion.

In addition, considering the improvement of fiber treatment efficiency, the suitable heat treatment temperature should be higher than 250 C.