A Simple, Low-Cost, and Green Method for Preparing Strong, Tough, and Ductile Poly(lactic acid) Materials with Good Transparency and Heat Resistance

Abstract

Notwithstanding that unprecedented progress has been achieved in strengthening and toughening PLA materials, it is still a challenge to find a facile and low-cost way to improve poly(lactic acid) (PLA) strength, toughness, and ductility while maintaining transparency and biodegradability. Herein, strong, tough, transparent, and highly heat-resistant PLA materials with a nacre-like lamellar structure were fabricated via a simple, low-cost and additive-free pressure-driven flow process. PLA powders with a size under 500 μm and heterogeneous size distribution obtained from ball milling and size sieving were used to yield a PLA material with a dense and ordered crystalline structure after pressure-driven flow treatment. The newly formed structured PLA material exhibited exceptional mechanical properties, with tensile strength, elongation at break, impact strength, and tensile toughness reaching 88.9 MPa, 102.5%, 45.1 KJ/m2, and 81.2 MJ/m3, respectively. The refined strength, toughness, and ductility were attributed to more particles undergoing uniform plastic deformation during the pressure-driven flow treatment. The interface between particles in the powder was much larger and more tortuous, and the particles were firmer. Additionally, the newly formed tightly stacked crystal structure consisting of densely and orderly arranged nanosized crystals played an important role in improving the mechanical properties of PLA. Moreover, the newly formed structured PLA materials exhibited enhanced heat resistance and retained good transparency, with a visible light transmission of over 80%. Overall, this work presents a simple and efficient method for fabricating high-performance PLA materials that are strong, tough, ductile, transparent, heat-resistant, and easily recyclable.