Properties of Thermoplastic Starch/Poly (Lactic Acid) Blends

Abstract

Properties of plasticized thermoplastic com and pulse starches and their blends with poly (lactic acid) (PLA) were studied. Water and glycerol acted as plasticizer components for a ratio of starch/glycerol/water (wt/wt) fixed at 50/36/14 based on previous studies. PLA was used in blends to improve the properties of thermoplastic starch (TPS). Maleic anhydride (MA) was used as a coupling agent to increase the miscibility of PLA and TPS phases. Cloisite 30B, a type of organoclay, was added into the material system to improve the properties of blends. In order to enhance the hydrophobicity, alkyl ketene dimmer (AKD), used as a sizing agent, were introduced to material system. Both internal and surface sizing methods were applied. Measurements of rheological and mechanical properties were performed on a Rosand capillary rheometer and Instron tensile testing machine. The thermal and morphological properties of blends were characterized using differential scanning calorimetry and scanning electron microscopy. The contact angles were measured using a goniometer equipped with a video camera and a computer with drop shape analysis software for calculating the contact angles. The use of maleic anhydride as a coupling agent significantly improved the tensile strength and modulus of blends and the blend morphologies were more homogeneous. Improvements in tensile strength and modulus were achieved as Cloisite 30B nanoclay was used as a filler in TPS/PLAgMA blends. Some hydrophobicity was obtained for blends with Cloisite 30B. Blends ofTPS/PLAgMA/clay showed shear-thinning behaviors at 150°C . .