Characterization of bioplastics poly (lactic acid) blended with thermoplastic starch

Abstract

This research was concentrated on characterized mechanical properties and adjusted compatibility of poly (lactic acid) (PLA) with thermoplastic starch (TPS) as biodegradable polymers composites. PLA was blended with TPS at the proportion of 10, 20, 30, 50, and 70 wt% as well as 2 phr chain extender by an internal mixer at 200°C. The blended materials were then injection molded at 230°C. Tensile testing showed that as the amount of TPS increase, the elongation at break tended to increase but the tensile strength and modulus tended to decrease. The morphology was investigated by scanning electron microscope. It was found that distinct phase between PLA and TPS was observed. Yet, adding the chain extender clearly improved the compatibility between PLA and TPS. The blended materials were also analyzed by differential scanning calorimetry method to study thermal properties. It was found that, as the amount of TPS increased, the glass transition temperature (Tg), melting temperature (Tm), and cold crystallization temperature (Tcc) deceased. Additionally, chain extenders did not affect thermal properties. The thermal stability of the composites decreased when increasing the amount of TPS because of the degradation of TPS in PLA. However, when heated at 100ºC for 1 hr, the PLA sample bent while TPS did not bend. When PLA was mixed with TPS, the composite was bent according to adding TPS.