The effect of short heat treatment on different properties of PET fiber using double beam interference microscopy.

Pluta microscope used to throw light on the effect of heat treatment time on the different properties of poly (ethylene terephthalate) PET fibers. PET fibers were annealed at times ranged from 5 to 30 min at different temperatures (150, 170, 190, 210°C) using two different processes (fast cooling and slow cooling processes) in air. The refractive indices, the shrinkage, orientation factor and crystallinity of PET fibers were determined for different annealing temperature during the short time treatment. The shrinkage percentage and degree of crystallinity increased with increasing the temperature and time of annealing. Microinterferograms are given for illustration.