This research investigates the influence of heat-treatment tension on structural properties of high modulus low shrinkage ( HMLS) industrial polyester fibers in post-processing. HMLS industrial polyester fibers was subjected to heat treatment with various tensions (0-0. 10 cN/dtex) at 150 ℃ for 5 min. The conformational changes of the samples before and after the heat treatment were analyzed, and the structural factors regulating their properties were discussed. The results show that with the decrease of pre-tension, the breaking strength remains basically unchanged, the tenacity decreases slightly, the initial modulus and the tenacity at the specific elongation of 5. 0% decreased obviously, and ultimate elongation increased significantly. The microstructure changes caused by the heat-treatment mainly occur in the amorphous chains, causing lower orientation in the amorphous region, lower trans conformation content, smaller lamellar long period and smaller amorphous thickness. The presence of pre-tension can effectively offset the shrinkage stress of the fiber, decreasing the mobility of molecular chains in the amorphous region, and the degree of mechanical properties and structure changes in the amorphous region is reduced.
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