High‐Performance Waste Seashell Powder Reinforcing Poly(lactic acid)/Poly(butylene adipate‐co‐terephthalate) Tubes: Synergistic Toughening of Preferential Alignment and Annealing

ABSTRACT Benefiting from the exceptional biodegradability and biocompatibility, poly(lactic acid) (PLA) demonstrates promising potential in polymer tubes, yet its wide application is constrained by high material costs and suboptimal mechanical properties. In this study, a low‐cost, ductile, and robust waste seashell powder (WSP) reinforcing PLA/poly(butylene adipate‐co‐terephthalate) (PBAT) composite tube was fabricated via a synergistic strengthening and toughening strategy of flow‐induced orientation and annealing. During extrusion, a dual‐directional flow field was constructed via the synchronized rotation of the mandrel and die, triggering a stacked configuration of WSP along the radial direction, constructing a nacre‐like structure in PLA/PBAT tubes. This nacre‐like alignment demonstrated enhanced endurance to external stress, endowing the tubes with optimized radial mechanical performance. Furthermore, annealing was applied to induce the conformational regulation of PLA, contributing to the boosted toughness of the tubes. The synergistic strategy realized the synchronous enhancement of radial strength and toughness, manifesting as a considerable elevation of 94%, 143%, and 124% in cyclic compression strength, low‐temperature impact energy, and elongation, respectively, compared with conventionally extruded tubes. This study proposes an effective strategy to fabricate high‐performance PLA‐based tubular products, thus broadening their application in fields such as medical implants, precision agriculture, and high‐end packaging.