Preparation and properties of polylactic acid and cassava starch blends using citrates and formamide

Abstract

Formulation and method for preparation of biodegradable plastics by blending of poly (lactic acid) (PLA) with at least 50% of low cost cassava starch are investigated using a single screw extruder. Formamide and water are tested as a plasticizer for cassava starch to form low crystallinity thermoplastic starch (TPS) while triethyl citrate and tributylacetyl citrate are used as a compatibilizer for the PLA/TPS blends. The tensile strength and DSC thermograms suggest that pure formamide is better than aqueous formamide solution for the preparation of amorphous TPS. The TPS/PLA blends generally have poorer mechanical properties and lower deformation temperature comparing to virgin PLA. The SEM images reveal that there is some phase separation between PLA and starch in the blends, especially at higher starch contents. The interfacial modification of PLA/TPS blends by using tributylacetyl citrate is better than triethyl citrate in promoting the miscibility between the starch and PLA that is important for improving the mechanical properties of the blends to acceptable level. However, increases the used amount of the citrate compatibilizers significantly decrease the deformation temperature of the blends.