Biaxially-Stretched Poly(Lactic) Acid (PLA) and Rubber-Toughened PLA Films: Tensile and Physical Properties

Abstract

Poly(lactic) acid (PLA) is bioplastic produced from corn starch; its brittleness limits the use of PLA in many applications. Biaxial stretching is one approach adopted by film manufacturers to enhance the properties of plastics such as polypropylene (PP). This study aims to produce biaxially-oriented PLA films which had been toughened with 1-10% core-shell rubber (CSR). Differential scanning caloriemetry (DSC) results indicated that all biaxially-stretched neat PLA and the PLA/CSR films possessed nearly 20% greater crystallinity than the as-cast film.The yield stress of the biaxially-stretched films were higher than that of the unstretched films in both machine (MD) and transverse (TD) directions. After biaxial stretching, the elongation at break of the stretched films was still much higher than that of the unstretched ones. The tear resistance was highest in the film with 5 wt% CSR, it became higher after biaxial stretching. The water vapor permeation (WVP) was also minimum in the film with 5 wt% CSR. The biaxially-stretched films had lower WVP than the unstretched ones due to the enhanced crystallization and chain orientation in the stretched films.