Ageing of poly(lactic acid) films plasticized with commercial polyadipates

Abstract

BACKGROUND: Amorphous poly(lactic acid) (PLA) was plasticized with two polyadipates with different molar masses. Some physical properties were studied over time to evaluate the stability of these blends. The aim of this study was to improve PLA ductility and consider the feasibility of its use in flexible films for food packaging. RESULTS: The addition of polyadipates caused a decrease of the glass transition temperature (Tg) and an increase of PLA chain mobility. Samples with Tg values above the storage temperature suffered physical ageing with a reduction in free volume. All the unaged blends were mainly amorphous, but samples with Tg below the storage temperature developed crystallinity during ageing leading to phase separation. Ductile properties of films improved with plasticizer content immediately after blending, but there was a deterioration in such properties upon ageing due to matrix densification and crystallization of PLA chains. CONCLUSION: PLA can be efficiently plasticized by polyadipates and the results have shown that some of the prepared films remain flexible with no phase separation after 150 days.