Improvement of Mechanical Properties for Poly(L-lactic acid) Film through Drawing Process Optimization

Abstract

The enhancement of tensile strength and elongation of poly(L-lactic acid) without using additives has been awaited to open new environmentally friendly markets. To improve the brittle mechanical properties of poly(L-lactic acid), we have investigated the effect of draw ratios and process temperatures on the mechanical properties. The results suggested that tensile strength linearly increased as a function of draw ratio, but elongation at break had a maximum value around draw ratio 2. It was found that the mechanical properties of the films were strongly affected by the draw ratio and not by the process temperature. Δn increased as a function of draw ratio up to 4 (the highest limit of the present test). These results allowed us to interpret that the mechanical properties reflected mainly molecular orientations in the amorphous regions, which were governed by the draw ratio.