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Polyurethane Prepolymer Modified Cassava Starch Based Poly(butylene adipate‐co‐terephthalate) Composites with Excellent Compatibility and High Toughness

In this study, a high‐efficiency polyurethane prepolymer (PUP) compatibilizer is developed to improve the compatibility between cassava starch and poly(butylene adipate‐co‐terephthalate) with higher molecular weight (MPBAT). Preferentially, modified starch (MS) is prepared by reacting isocyanate groups of PUP with hydroxyl groups of starch in a high‐speed mixer, and then starch‐based MPBAT composites (MSPT) with PUP as a compatibilizer are continuously extruded using twin‐screw extruder. The mechanical properties, water absorption, and thermodynamic properties as well as morphology of MSPT are investigated with different PUP contents and at the same mass ratio of MPBAT to starch (1:1). Samples of MSPT‐2 provide satisfactory mechanical properties comparable to control samples. Addition of 13 wt.% PUP to MSPT, improves tensile strength from 3.8 to 11.9 MPa and increases elongation at break from 93.3 to 580.4% at room temperature compared with control without the PUP. The hydrophobicity and thermostability properties of MSPT‐2 composites are also enhanced. The results further prove that MSPT‐2 composites possess excellent compatibility, not only because of the urethane bonds of the PUP and starch, but also stemming from the physical crosslinking between soft segment of PUP and aliphatic segment of MPBAT. Starch‐based MPBAT composites with excellent compatibility and high toughness will help broaden the application field of biodegradable plastics.