The rheological behaviors, aging properties, and thermal stability of chain extended poly(butylene adipate-co-terephthalate)

In this work, a one-step reactive extrusion method was adopted to improve comprehensive properties of poly(butylene adipate-co-terephthalate) (PBAT) by melt blending with two chain extenders, including polycarbodiimide (PCDI) and multi-functional epoxy polymer (ADR). Their influences on rheological behaviors, aging properties, and thermal stability of PBAT were explored, and the detailed mechanisms were also discussed. It was found that the terminal carboxyl content of PBAT decreased with addition of PCDI and ADR. When 1.0 wt% PCDI was added, the terminal carboxyl content deceased by 70.3%. This indicated that the reaction between the two chain extenders and the terminal hydroxyl and carboxyl groups of PBAT enhanced to perform the chain extension, which increased the molecular weight, storage modulus, loss modulus, and complex viscosity of PBAT, and different relaxation processes were observed for different samples by Han and Cole–Cole plots. Damp-heat aging resistance measurements showed correlation with terminal carboxyl content in PBAT. And reducing the terminal carboxyl content in PBAT was shown to increase hydrolytic stability. For PBAT with 1.0 wt% PCDI blend, the tensile strength and elongation at break retention were above 70%. In addition, the thermal stability of PBAT was also improved due to the chain extension in the blends, which retarded degradation. The analysis results indicated that the comprehensive performance of modified PBAT was the best when 1.0 wt% PCDI was added.

Graphical abstract