Properties of Starch/PBAT Composites: Comparing High‐Amylose Corn Starch and Cassava Starch

ABSTRACT To investigate the effect of amylose content on the mechanical properties, thermal performance, and microstructure of starch/PBAT composites, two types of starch/PBAT composites were prepared using compression molding. The study evaluated the composites' mechanical properties, thermal expansion coefficient, static contact angle, moisture absorption, and microstructure using scanning electron microscopy. The findings revealed that the flexural strength of the high‐amylose corn starch/PBAT composite was greater than that of the cassava starch/PBAT composite. However, the cassava starch/PBAT composite, which contains highly branched starch, demonstrated superior tensile and impact properties. Notably, the impact strength of this composite reached its peak when the cassava starch content was 30 wt%, which represented a 95.5% improvement compared to the unmodified composite. In terms of microstructure, the impact fracture surface of the high‐amylose corn starch composite exhibited a distinct layered structure with pronounced cracks, unlike the smoother fracture surface of the cassava starch composite. Furthermore, the high‐amylose corn starch/PBAT composite showed a higher moisture absorption rate than the cassava starch counterpart. Regarding thermal properties, the linear expansion coefficient of the composite containing 50 wt% high‐amylose corn starch was consistently lower than that of other composites at 48°C. The addition of starch is typically accompanied by a red shift in the PBAT ester carbonyl C = O absorption peak, which serves as direct spectroscopic evidence of stronger hydrogen bonding interactions within the system.