It is critical to prepare ductile and hydrophobic modified starch material in an effective and environmentally friendly way. In this work, polyurethane prepolymers (PUPs) with various isocyanates were synthesized and mixed reactively with thermoplastic starches (TPS) in an intensive mixer to prepare modified TPS. The effects of the isocyanates on the structure and properties of the modified TPS were then investigated by using scanning electron microscope (ESEM), tensile tester, and contact angle meter. Results showed that mechanical properties of the modified TPS were improved with the increase in hydrophobicity of the isocyanate. 4,4 0 -Methylenedi-p-phenyl diisocyanate (MDI) was hydrophobic, the NCO groups in PUPs were not easily consumed by water when modified starch was prepared, leading to a significantly increased reaction of the NCO groups with starch. As the amount of urethane bonds between starch and PUP increased, the compatibility between the two polymers was also improved, resulting in the improvement of tensile properties. Isocyanates played an important role in improving the compatibility between the starch and PUP and the properties of the modified TPS.

No 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.

No abstract