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Keywords:

  • degradation;
  • hydrolysis;
  • mechanical properties;
  • migration;
  • poly(lactic acid);
  • thermophysical properties

Abstract

Control of the durability of commercial biodegradable materials when used as food packaging is relevant to guarantee the safety of food. The service life performance of a commercial material based on poly(lactic acid) was assessed through an aging test which mimics its real use (immersion in water at 40 °C for up to 6.5 months). The ability of different techniques for the evaluation of polymer decomposition was investigated and two types of degradation were shown, a reversible physical aging and a permanent deterioration due to hydrolysis. Physical aging was reflected in differential scanning calorimetry scans by increased glass transition temperature and corresponding enthalpy. A gradual decrease of crystallization temperature and increase of melting temperature and crystallinity were also observed. The progressive loss of mechanical properties reflected the sum of both types of degradation. Hardness, flexural modulus and flexural strength were more sensitive to deterioration than strain. The highest toughness of the material was achieved at two months. The cleavage of polymer chains and release of substances caused increased migration levels, especially marked for long time periods. Water uptake and migration levels followed a concordant pattern and experienced the highest increases. A simple protocol for quality control based on the obtained results is suggested. Copyright © 2012 Society of Chemical Industry