Physical Properties of Stereocomplex Type Poly(lactic acid) Biaxially Drawn Films

Abstract

Equal amounts of PLLA and PDLA were melt-mixed in a mill type mixer at 190 ̊C and further extruded at 250 ̊C. The blend obtained was compression molded into films and biaxially drawn and annealed. The changes in various physical properties such as mechanical and thermal properties and the higher-order structure of the films in the biaxial drawing and annealing processes were investigated. The biaxially drawn films showed a broad crystalline WAXD reflection similarly to the uniaxially drawn PLLA/PDLA blend fibers and the application of annealing at 190 ̊C completely changed the reflections into those of SC. The higherorder structure was completely transferred into SC after annealing at an elevated temperature. The mechanical property was improved by the biaxial drawing and the annealing for short period of time, and the films showed an excellent thermal resistance. However the annealing for a long period deteriorated the mechanical property.