Controlling grafting density of compatibilizer to enhance performance of thermoplastic Starch/Poly(butylene adipate-co-terephthalate) blends

The wide utilization of thermoplastic starch (TPS) as a sustainable alternative to conventional plastics is hindered by its high hydrophilicity, which limits compatibility with biodegradable polymers that are hydrophobic, such as poly(butylene adipate-co-terephthalate) (PBAT). Addressing this challenge, we introduce an innovative two-step blending process that effectively controls grafting density of a compatibilizer within a TPS/PBAT blend to enhance their interfacial compatibility without compromising the low-cost advantage of TPS. We synthesized a reactive compatibilizer, poly(ethylene glycol methyl ether acrylate-co-glycidyl methacrylate) (EG), which was systemically located within the TPS phase. By controlling the grafting density of PBAT onto EG by adjusting the melt-blending duration (0, 5, 10, 20, and 40 min), we successfully modified the affinity of the compatibilizer for the blend components and controlled its migration toward the PBAT phase. Adjustment of the duration of the pre-grafting of PBAT onto EG significantly influenced the distribution of the TPS domains throughout the blend. The blend that incorporated the compatibilizer pre-grafted for 20 min (blend B20) had the smallest domain size and maximum tensile strength. Additionally, this particular blend exhibited the highest complex viscosity and storage modulus among the compatibilized blends, along with significantly improved water barrier properties, thereby indicating effective compatibilizer anchoring between TPS and PBAT. Our findings underscore the potential of this two-step blending approach to design the optimal compatibilizer for the TPS blends, paving the way for their broader application in sustainable material development.