Abstract
Thermoluminescence (TL), differential scanning calorimeter (DSC) and stress-strain (S-S) curve were studied for polypropylene (PP) fibers irradiated with ultraviolet (UV) rays.
As for the samples which were irradiated with UV rays for 2 to 8 hours, a TL peak was observed at about 110°C. By contrast, UV irradiation over 10 hours gave rise to an appearance of luminescence peak at around 160°C, which could be ascribed to the suitable crystals.
It seemed that the two types of PP crystal play an important role as a trap of the excited electron and released some of trapped electrons emitting thermoluminescence in the temperature range of crystalline dispersion and melting. Two endothermic peaks on DSC were observed. The intensity of the lower peak decreased with an increase of UV irradiation time, being correlated with the TL behavior.
The breaking point on S-S curve was shifted to the lower strain side by this UV irradiation almost along the curve of the unirradiated fiber, and reached the yielding point after UV irradiation for 8 hours.
TL was thus proved to be one of the useful techniques for investigation of UV degradation on fibers.
