Mechanically Robust Wasted Seashell-Filled Poly(lactic acid)/poly(butylene adipate-co-terephthalate) Composite via In Situ Reactive Compatibilization and Conformational Transition

Shellfish shell as an aquaculture byproduct is usually abandoned randomly after consumption, leading to heartrending resource waste and severe environmental pollution. At present, blending waste seashell powder with biodegradable polymers is a potentially efficient method of green recycling, but the unsatisfactory mechanical properties from poor interfacial compatibility and serious filler agglomeration limit its potential application. Here, a multifunctional epoxy-based chain extender was used as an in situ reactive compatibilizer to reinforce the interaction of poly(lactic acid)/poly(butylene adipate-co-terephthalate) (PLA/PBAT) composites filled with waste seashell powder (WSP) via the straightforward melting blend, followed by the annealing treatment above the glass transition temperature. Surprisingly, the epoxy groups in chain extenders could not only react with the terminal groups in PLA and PBAT but also interact with hydroxyl-rich WSP for efficient in situ compatibilization. In addition, induced by the annealing treatment at 80 °C, the formation of a high-energy gauche–gauche (gg) conformer in PLA molecules further improved the impact properties of the composite. Ultimately, under the synergy between enhanced interphase combination and increased gg conformer, the tensile strength and impact strength increased by 53 and 76%, respectively, compared to that of the sample without compatibilization and annealing. Green composites are highly suitable for packaging products because of their obvious advantages, including reliable mechanical performance, cost-effectiveness, and biodegradability. This work introduced an implementable and efficient route for the upcycling of waste seashells.