Effect of polyvinyl acetate on the properties of biodegradable thermoplastic starch/polyethylene glycol blends

Abstract Thermoplastic starch (TPS)/polyethylene glycol (PEG)/polyvinyl acetate (PVAc) blends were prepared through melt blending, in which PEG content was fixed at 5 wt% and PVAc content ranged from 10 wt% to 20 wt%, with increments of 5 wt%. For comparison, a TPS/PEG blend was also prepared. All the blends were subsequently characterized using various techniques. Differential scanning calorimetry (DSC) results showed that the melt temperatures ( T m ) of TPS and PEG in all blends remained independent, indicating immiscibility of TPS and PEG. Notably, T m of TPS weakened upon the addition of PVAc, and the effect was particularly pronounced in the blend containing 15 wt% PVAc, whose T m disappeared and a cold crystallization temperature ( T cc ) emerged, suggesting a crystal hindering effect exerted by PVAc on TPS. X-ray diffraction (XRD) results further supported this finding, showing that PVAc primarily inhibited the formation of V A -type crystals in TPS and slightly increased starch retrogradation. Scanning electron microscopy (SEM) images revealed that starch plasticization increased with higher PVAc content, and TPS particles agglomerated into larger nodules. Tensile testing demonstrated that the ternary blends exhibited enhanced strength, while PEG did not contribute to the toughness of the system. Additionally, the thermal resistance, equilibrium moisture adsorption, and biodegradation stability of the ternary blends improved with the incorporation of PVAc. It is evident that in TPS/PEG/PVAc ternary blends, PVAc retained its reinforcing and crystallinity-reducing effect, whereas the toughening effect of PEG was absent.