Poly(lactic acid): plasticization and properties of biodegradable multiphase systems

Poly(lactic acid) (PLA) is a biodegradable aliphatic polyester well suited for disposable applications. PLA was plasticized with various biocompatible plasticizers. Their efficiency was evaluated in terms of glass transition temperature (Tg) shift and mechanical properties improvement. Significant decrease in Tg and rise in the elongation at break was obtained with polyethylene glycol and oligomeric lactic acid. Furthermore, PLA was melt-blended with thermoplastic starch (TPS). The properties of subsequent TPS/PLA blends were investigated through tensile and impact testing, thermal analysis (DSC), dynamic mechanical analysis and microscopy (SEM). From the mechanical results, low level of compatibility was found. The blends showed two distinct Tgs. However, the PLA phase varied toward the Tg of TPS with the blend composition, indicating some degree of interaction. Microscopic observations revealed non-uniformly dispersed PLA inclusions in the TPS matrix, confirming that phase separation has occurred.