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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. [ABSTRACT FROM AUTHOR]

Abstract: With the aim of develop new materials for active food packaging, composites of low-density polyethylene (LDPE) with chitosan (CS) or chitosan sodium montmorillonite clay nanocomposites (CSnano), with or without Irganox 1076 commercial synthetic antioxidant or vitamin E (VE) as natural antioxidant were prepared by melt processing. The obtained materials have been characterized by processing behavior, mechanical and thermal properties, positive groups determination, atomic force microscopy and standard tests to assess antimicrobial and antioxidant activities. The compositions assuring insignificant decrease in mechanical and thermal properties were selected as LDPE/3CSnano/VE and LDPE/6CSnano/VE. It has been shown the chitosan imparts antimicrobial properties to LDPE films while the vitamin E increased the oxidation induction period, especially for materials containing chitosan nanocomposites. The incorporation of both chitosan nanocomposites and vitamin E in polyethylene gave films with good antimicrobial and thermal properties because of significant increase of charge surface and important changes in surface topology and antimicrobial activity because of a synergistic effect. The nanocomposites cannot only passively protect the food against environmental factors, but they may enhance shelf life of food products. [Copyright &y& Elsevier]