Effects of electron beam irradiation on thermal and mechanical properties of poly(lactic acid) films

The purpose of this study is to examine the effect of electron-beam (EB) radiation on biodegradable polylactic acid (PLA), and to understand radiation-induced degradation mechanisms. PLA films were irradiated between 0 and 120 kGy and physical properties were characterized by means of GPC, DSC, DMA and tensile drawing. It was shown that degradation of PLA under EB leads to a random chain scission responsible for a reduction of the molar mass. These molar mass changes affect glass transition temperature T-g, degree of crystallinity, and mechanical properties. It was found that T-g, stress and strain at break decrease with increasing irradiation dose, whereas the degree of crystallinity increases up to 45 kGy then decreases. Cross-linking G(x), and chain scission G(s) values of PLA revealed that chain scission reactions at lower dose predominate over cross-linking. DMA results exhibit an exothermal re crystallization for neat and irradiated samples, which disappears with increasing heating rate. These results were confirmed by DSC measurements. Ductile-brittle transition was determined as function of EB-dose and crosshead speed. A change of physico-chemical and mechanical properties was evidenced during application of a dose of 45 kGy. (C) 2016 Elsevier Ltd. All rights reserved.