Rheological analysis of chain extension reaction in PBAT-microalgae composite and its effect on film fabrication

Abstract

In this study, we investigate the reaction of an epoxy-based chain extender in poly(butylene adipate-co-terephthalate) (PBAT) composites incorporating protein-rich microalgae, Chlorella sp. HS2. The chain extension reaction in the PBAT/HS2 system is systematically characterized using rheological and gel permeation chromatography analyses, showing that the addition of HS2 significantly changes reaction kinetics because HS2 induces PBAT degradation and also actively participates in the reaction with the chain extender. Under heat, the chain extender with epoxy functional groups actively reacts with degraded PBAT molecules through thermal decomposition and microalgae incorporation, restoring PBAT, while simultaneously facilitating interfacial bridging between PBAT and HS2. As the content of the chain extender increases, the chain extension reaction leads to a more structural evolution and induces molecular branching, resulting in strong shear thinning and strain hardening behavior. The effect of chain extension improves film processing of PBAT/HS2 composites. T-die extrusion demonstrated the feasibility of film production, emphasizing the industrial applicability of the newly formulated composites. The findings underscore the crucial role of advanced rheological strategies in characterizing reactive compatibilization between biodegradable polymers and natural fillers.