Physical and polymeric structure of polyesters

Physical and polymeric structure of polyesters

The morphological structure observed under the microscope of the polyester obtained by melt spinning is a circular cross-section without special longitudinal structure. Filamentous fibrils can be observed under an electron microscope.

Shaped fiber can change the elasticity of the fiber, endow the fiber with special luster and bulkiness, improve the cohesion and coverage of the fiber, as well as anti-pilling and reduce static electricity. For example, the triangular fiber has a sparkling effect; the five-leaf fiber has a bright luster, a good hand feel, and is not easy to pill. The inner density of the hollow fiber is small, and the warmth retention property is good.

fold aggregate structure

The thickness of polyester folding chain crystals was measured by electron diffraction to be about 10 NM, and the length of polyester single base was 1.075 NM. Therefore, the thickness of the lamellae is considered to be equivalent to the single base length of 9 polyester molecules. However, the polyester macromolecular chain length is about 1.075*130 (average degree of polymerization) = 140NM, so it can be seen that the polyester sheet macromolecular chain must adopt a folded chain structure. Folding may occur in the -CH2-CH2- segment because the chain is flexible and bends easily.

In addition, extended chain crystals (fibrillated crystals) can also be formed due to polyester macromolecules. It can be seen that folded chain crystals and fibril crystals coexist in polyester. The ratio of the two crystals depends on the draw ratio and heat setting conditions.