Effect of thermal and mechanical processes on the molecular orientation ofpolyester fibres

This study uses the optical results obtained by a double-beam interference polarized microscope connected to a mechanical device to measure the molecu lar orientation produced in polyester (PET) fibres. The samples were boiled for various periods of time and stretched at room temperature. The changes in the molecular orientation were evaluated to obtain the values of three orientation functions. The results of the extension were used to calculate some mechanical factors and the shrinkage stress. In addition, the crystall ine and amorphous orientation functions, the dielectric constant, the diele ctric susceptibility and the number of moles of network chains per unit vol ume were among the calculated parameters. The present work throws light on how the thermal treatment and the applied stress affect the molecular orien tation factors and the calculated structural parameters. Relationships amon g the calculated parameters and both the draw ratios and the boiling time a re given, for illustration.