Degradation of different polystyrene/thermoplastic starch blends buried in soil

Blends of PS and TPS were prepared using two different plasticizers: glycerol or buriti oil by solvent casting technique. PS/TPS blends were submitted to degradation by soil burial tests in perforated boxes for 6 months and later analyzed by TG and CPMAS C-13 NMR. After degradation, blends with glycerol presented less stages of thermal degradation and NMR signals of minor intensity compared to the original blends. The presence of TPS at contents of 50% or greater improved the degradation of the blends. After 6 months, PS/TPS blends with buriti oil presented only one thermal degradation stage with a significant increase in mass loss. Moreover, all absorptions related to starch disappeared in NMR spectra after soil buried test, probably due to the consumption of starch by microorganisms. These results revealed that PS's degradability can be improved when TPS plasticized with buriti oil is added to it. (C) 2008 Elsevier Ltd. All rights reserved.