Abstract
Effects of isothermal temperature on mechanical properties of polyester filament during melt spin-draw system were studied. Tenacity decreased, but elongation increased with the increase of isothermal temperature from 130℃ to 250℃. Velc showed minimum value at isothermal temperature of 210℃. Young's modulus and crystallinity as a function of isothermal temperature showed a similar pattern, in which Young's modulus and crystallinity increased to 127 Eld and 0.455, respectively, as the isothermal temperature increased, and then decreased. The maximum values in both cases appeared at the isothermal temperature of 190℃ due to the fastest crystallization at this temperature. Apparent crystallite size in the b-axis direction was larger than that related to the a-axis irrespective of isothermal temperature. Apparent crystallite size in the b-axis direction had almost the same values 58 A as a function of isothermal temperature from 150℃ to 250℃.