Crystalline behavior and rheological behavior of polylactide/sisal fiber biocomposites via in‐situ reaction with epoxy‐functionalized oligomer and poly (butylene‐adipate‐terephthalate)

Abstract Polylactide/sisal fiber biocomposites (PLA/SF) were synthesized through in‐situ reactive melt mixing with poly (butylene‐adipate‐terephthalate) (PBAT) and epoxy‐functionalized oligomer (ADR). The PBAT plasticized the PLA matrix, reducing the cold crystallization temperature ( T cc ) in the PLA/PBAT/SF composites, as demonstrated by differential scanning calorimetry. Enhanced interfacial interactions within the composites restricted chain mobility, leading to a shift in T cc of PLA/PBAT/SF/ADR towards higher temperatures. Isothermal crystallization kinetics analysis using the Avrami equation revealed that introducing ADR into the blended system increased the semi‐crystallization time of the composite system while reducing the crystallization growth rate and crystallization ability. Rheological analysis indicated that both the loss and storage modulus increased when ADR and PBAT were incorporated into the blended system, particularly with the addition of ADR. The incorporation of PBAT and ADR produced a more gel‐like rheological behavior in the blends. ADR induced an in‐situ reaction that augmented interfacial forces and enhanced molecular chain entanglement. Additionally, sisal fibers served as physical crosslinking points, suppressing the stress relaxation of polymer molecular chains. The appearance of long relaxation time structural units within PLA/PBAT/SF/ADR blended systems enhances their elastic response. This study focuses on the impact of the in‐situ reaction on the crystalline and rheological behaviors of the composite system. Highlights ADR strengthened adhesion among PLA, PBAT, and SF, significantly increasing the cold crystallization temperature of PLA/PBAT/SF/ADR. Reactive processing reduced the crystallization rate of the composites. The incorporation of ADR and PBAT improved the blended system's loss and storage moduli. ADR‐induced in‐situ reactions enhanced the shear‐thinning behavior and elastic response of the composites. PBAT and ADR improved the melt strength and processing performance of the composites.