Thermoplastic starches modified with polyurethane microparticles: The effects of isocyanate types in polyurethane

Abstract In this work, polyurethane prepolymers (PUPs) with different isocyanate types were synthesized and mixed reactively with a starch–water mixture to prepare modified thermoplastic starch (TPS). The effects of the polyurethane isocyanate on the structure and properties of the modified TPS sheets were then investigated. Results from the scanning electron microscope (SEM), FTIR, mechanical tests, and contact angle (CA) confirmed that the modified TPS possessed a homogenous structure, good compatibility between starch and polyurethane (PU), excellent toughness, and hydrophobicity. The degradation experiment also revealed that the PU could be completely separated from the modified TPS. Additionally, almost 100% of the PU particles were cross‐linked to starch matrix, indicating the high efficiency of the modification. The NCO groups with higher reaction activity exhibited a higher number of urethane linkages between the starch matrix and the PU microparticle, resulting in improved compatibility of the two phases of the modified TPS and an increase in toughness.