The effect of polyethylene glycol sorbitan monostearate on the morphological characteristics and performance of thermoplastic starch/biodegradable polyester blend films

Although thermoplastic starch (TPS) has been developed to mitigate greenhouse gas emissions and environmental and health-related impacts from plastics, high moisture sensitivity and poor mechanical properties limited its practical applications. Blending TPS with biodegradable polyesters, i.e., poly(lactic acid) (PLA) and poly(butylene succinate-co-butylene adipate) (PBSA), is an alternative approach; however, the compatibility among polymer phases needs to be improved. Here, polyethylene glycol sorbitan monostearate (Tween 60), an amphiphilic surfactant, was proposed to improve the compatibility and performance of the TPS/PLA/PBSA 40/30/30 blend. The concentration of Tween 60 varied in the range of 0.5-2.5 wt%. The blends were fabricated using an extruder through two different melt-mixing routes, i.e., direct mixing and masterbatch mixing, and then converted to film using a blown film extrusion line. Tween 60 could improve compatibility between TPS dispersed phase and PLA/PBSA matrix, resulting in increased tensile strength, extensibility, impact strength, thermal stability, and water vapor and oxygen barrier properties of the ternary blend. In addition, better performance of the blend was obtained from the direct mixing route. Tween 60 could thus be considered a potential compatibilizer for the TPS/PLA/PBSA blend film, which can be further used as a biodegradable packaging material.