Plasticized hydroxypropyl cassava starch blended PBAT for improved clarity blown films: Morphology and properties

Plasticized hydroxypropyl cassava thermoplastic starch (TPS) with glycerol was blended with polybutylene adipate terephthalate (PBAT) via blown-film extrusion. Effects of PBAT/TPS ratios (60/40 and 50/50) and degrees of substitution (DS) for hydroxypropyl groups in TPS on film properties were investigated. All PBAT/TPS blend films were determined for morphology, thermal stability, thermomechanical, mechanical and barrier properties. Higher DS increased film clarity and glossy surface, improved compatibility between PBAT and TPS, reduced crystallinity and enhanced exposure of hydroxyl groups and hydrogen-bonding of the films. Blending caused phase separation with dispersed starch granules in continuous PBAT matrices, giving high surface roughness. Increased TPS and DS facilitated formation of co-continuous structures and miscibility, improving elongation by approximately 210%. Different DS modified microstructure and hydrophilicity of PBAT/TPS films which consequently reduced water vapor permeability by 34%. Modified DS in hydroxypropyl starch efficiently improved clarity, mechanical and barrier properties of bioplastic packaging.