Starches modified with polyurethane microparticles: Effects of hydroxyl numbers of polyols in polyurethane

In this work, three different types of polycaprolactone (PCL) polyols-PCL diol, PCL triol and PCL tertol were used to synthesize polyurethane prepolymers (PUPs) with 4, 4′-methylenedi-p-phenyl diisocyanate (MDI). The obtained PUPs then were used to modify thermoplastic starch (TPS) in an intensive mixer. Results showed that the grafting ratio of PUP used for modified starch was 99.6 ± 0.2%, and the hydrophobicity of the modified starches improved compared to that of pure starch. With the increasing OH numbers of polyols in PUP, the compatibility between polyurethane and starch was improved. The toughness and thermal stability of modified starches were thus increased while the crystallinity of starch decreased. In addition, due to the existence of dense cross-linking, there was strong interaction between starch and PCL tertol based PUP, and the modified starch showed excellent toughness compared to pure starch. The superiorly formed, modified starch could have great potential applications.