Correlation between the activation energy of PLA respectively PLA/starch composites and mechanical properties with regard to differ accelerated aging conditions.

Abstract

Within this research semi-crystalline polylactide and composites with 50 wt.% native potato starch were compounded and injection molded. The material was mechanically characterized by tensile, three-point bending, and Charpy impact tests. These tests were carried out in the freshly molded state and after 332 and 792 h of storage at accelerated temperature or humidity. The respective activation energy was calculated by applying the Flynn-Wall-Ozawa method. The focus of the study was to investigate the correlation between the activation energy and the related mechanical and thermal properties. The results showed that the addition of native potato starch as a filler prevents the decrease in activation energy over the course of the experiments. Thus, the PLA/starch composite is more resistant to the two aging conditions than the pure PLA. When considering the mechanical properties, the pure PLA showed a large deviation of results compared to the initial value in a range of +63.88% to -33.96% with regard to the respective aging conditions, whereas the PLA/starch composite properties nearly always remained at the initial values. Through the investigation of the mechanical and thermal properties, it was shown that the steady activation energies are consistent with the mechanical properties, as these have shown only a small deviation of the mechanical properties during the duration of experiments for the PLA/starch composite.