Thermoplastic cassava starch blend with polyethylene-grafted-maleic anhydride and gelatin core-shell structure compatibilizer

Abstract

Thermoplastic starch (TPS) was prepared from cassava starch blended with glycerol (70:30 w/w). Gelatin (Gel) was incorporated into the TPS in water. The TPS/Gel was melt-blended with polyethylene-grafted-maleic anhydride (PEMAH). Maximum tensile strength of the TPS/PEMAH/Gel10 (29.3 MPa) increased significantly compared to the TPS/PEMAH blend (6.3 MPa), while elongation at break was 70%. The morphology of the TPS/PEMAH showed co-continuous morphology, while phase inversion occurred with the addition of Gel. The Gel was dispersed in the TPS matrix and covered the PEMAH. The TPS/PEMAH/Gel was nanoparticles (200 nm) in the TPS matrix. It showed two melting temperatures for PEMAH due to two structures with different crystal sizes. Melt viscosity of the TPS/PEMAH was enhanced with increasing Gel as the reaction induced chain extension. FTIR and rheology measurements confirmed the reaction between –NH groups of Gel and MAH groups of PEMAH. This reaction improved interfacial adhesion, morphology, and the mechanical properties of the blends.