Abstract
The isothermal crystallization of semicrystalline polymers and its blends have been studied for a long time, but there is less attention mention about the effect of gamma-ray irradiation on isothermal crystallization of semicrystalline polymers. In this research, the thermal properties, overall isothermal crystallization, spherulitic morphology and growth rate of non-irradiated and irradiated PESU were investigated by DSC and POM measurement and analyzed by Avrami equation and Lauritzen-Hoffman nucleation theory. The glass transition temperature of non-irradiated PESU is -19.9℃. The values of Tg increases with increasing of gamma-ray dose. The multiple melting behavior of PESU was observed after isothermal crystallization during DSC heating scan and the equilibrium melting temperature Tm0 was determined. The values of Tm0 decrease with increasing of gamma-ray dose. The overall isothermal crystallization rates of PESU increase with decreasing crystallization temperature from 70 to 35℃ but decrease at 30℃ as the same trend as the half time of crystallization t1/2-1 regardless of gamma-ray irradiation. The crystallization rate k of irradiated PESU is lower than that of non-irradiated PESU at the same crystallization temperature. Both non-irradiated and irradiated PESU show a maximum value of the growth rate and non-irradiated PESU being higher than that of irradiated at the same crystallization temperature. On the basis of LH theory, there is one transition between regime III and regime II was found at around 72.5℃ and the activation energy is 2.507 kJ/ mole. With the increasing of gamma-ray dose, the regime transition temperature decreases but activation energy increases. The values of t1/2-1 from DSC were used the same method to determined activation energy. The activation energy also increases with increasing of gamma-ray dose.