Chiang Mai Journal of Science

 Poly(ethylene terephthalate-co-lactic acid) (PET-co-PLA) copolymer with medium molecular weight was synthesized and blended with commercial polylactic acid (PLLA) by solution and mechanical blending methods to optimize its mechanical properties. Miscibility and properties of the blends were characterized. Miscible blends are achieved at all compositions. A decrease in storage modulus and T_g of the blends, compared to neat PLLA, indicates a plasticizing effect of the copolymer in the blends. Hydrolytic degradability of the samples is examined in phosphate buffer solution (pH 7.2) at 60°C.Appreciable degradability of the blends is retained despite the incorporation of aromatic esters. Anomalous degradation behavior of the samples in buffer medium is examined. Negative weight loss values and flocculation of the samples are clearly apparent at a specific hydrolysis time. This is due to the re-precipitation of degraded species onto the remaining solid sample. The copolymer and its blends show high potential for use in various applications, especially in packaging and agricultural fields.