Study of the soil burial degradation of some PLA/CS biocomposites

The chitosan effect on the soil burial degradation of polylactic acid plasticized with tributyl o-acetyl citrate (ATBC) was studied by weight loss measurements, changes in average molecular weight and its distribution, mechanical, thermal and surface properties correlated with structural and morphological modifications. Besides the loss of transparency at the end of environmental degradation test, all composites became brittle. During degradation, Young modulus increases while elongation at break significantly decreased, mainly for the biocomposites with high content of chitosan which also showed a significant decrease of average molecular weight, increase of glass transition temperature and crystallinity degree values and decrease of cold crystallization and melting temperature when soil burial period is longer. The high content of chitosan led to increased hydrophilicity of biocomposite surfaces which favors interaction with moisture and attack of microorganisms. Chitosan as hydrophilic compound promotes the soil burial degradation of PLA. However, longer period of soil burial are necessary for totally degradation of the sheets of plasticized PLA/CS biocomposites.