Published By: Blue Eyes Intelligence Engineering

Abstract — The article submits new experimental data pertaining to the role of combined heat-mechanically treatments on the birefringence and degree of crystallinity of amorphous uncrystallized but crystallizable poly (ethylene terephthalate) (PET) filaments. The heat-mechanically treatments of the investigated objects as well as the optical measurements were realized by specialized installations designed and built in the author’s laboratories. Undrawn PET yarns were subjected on heat-mechanically modification at constant temperature of 900C above their glass transition temperature (Tg) combined with tensile stress with values from 0MPa to 30MPa. Birefringence measurements and differential scanning calorimetry (DSC) were used in order to identify the occurred as a result of the heat mechanical processing the specimens ’ structural evolution. The optical measurements were carried out using the so called “P-F-A ” system involving polarization microscope and a CCD camera. It was established the influence of the superposition “annealing temperature/tensile stress ” on the filaments birefringence as well as the dominant effect of the tensile load on the fibers degree of crystallinity