The effect of thermal history induced by melt spinning on the mechanical properties of polylactic acid fibers

The Effects of thermal history during the melt spinning process on the mechanical properties and crystallinity of polylactic acid (PLLA) fibers have been studied. Thermal history applied on PLLA during the melt process caused the decrease of number-average molecular weights and this resulted in the lowering of orientation and crystallinity in PLLA fibers. As a result, the longer applied thermal history, the less tensile strength and modulus, and the higher elongation at break. It was also found that primary factor for controlling crystallinity of PLLA fiber was the stress induced crystallization while the thermal induced crystallization had a little effect on the crystallinity of PLLA fibers. However, the thermal induced crystallization turn out to be important in the crystallinity developed by annealing of PLLA fibers.