THERMOLUMINESCENCE STUDY OF THE CRYSTAL MODIFICATIONS OF POLYPROPYLENE FIBERS

Polypropylene fibres with different crystal modifications were investi gated using thermoluminescence (TL). Unirradiated, ultraviolet-irradia ted and gamma-ray-irradiated fibre specimens were studied from room te mperature to 200-degrees-C. It was found that the glow curves 6btained for fibres with both monoclinic and pseudohexagonal modifications hav e a sharp peak at the melting temperature, but the glow intensities fo r the fibres with the pseudohexagonal modification were much stronger than for the monoclinic ones. The TL glow peak at the melting temperat ure for the specimens with the pseudohexagonal modification was found to extend to a temperature as low as 100-degrees-C, suggesting that th e characteristic molecular motion may occur during the transition of t he crystal modifications. In addition, a weak TL peak was detected at about 65-degrees-C for the gamma-ray-irradiated specimens, which corre sponds to the temperature at which polypropylene achieves its maximum crystallization rate constant.