Fabricating highly hydrophobic thermoplastic starch/polyvinyl alcohol composites via twin-screw extrusion using citric acid–chitosan co-plasticizers

-acetylation reactions with TPS and PVA, forming a cross-linked structure. Incorporating CA and Cs improved TPS/PVA composite compatibility with inorganic fillers, enhancing surface smoothness and processing stability. However, ATR-FT/IR, viscometer, oscillating shear rheometer and DSC tests demonstrated that when CA addition exceeded 15 wt%, TPS underwent significant acid hydrolysis of glycosidic bonds, resulting in decreased viscosity and even the disappearance of crystallinity. The findings showed that when CA addition was 10 wt% (TC10), the mechanical properties of the TPS/PVA composite improved significantly; accordingly, its tensile strength, elastic modulus, flexural strength, and flexural modulus increased by approximately 200%, 660%, 290%, and 220%, respectively. Furthermore, TC10 exhibits remarkable hydrophobicity, with its contact angle increasing from 75° to 110°. CA-Cs co-plasticization addresses the migration problem of conventional low molecular weight plasticizers under high temperature, significantly enhancing blending uniformity, mechanical properties, and water resistance. TPS/PVA composites are expected to become an ideal choice for environmentally friendly products.