Suppressed Hygrothermal Aging of Toughened Biodegradable Polyester Films Achieved through Interfacial Reactions

Resistance to hygrothermal aging is a critical factor for the practical application of biodegradable polyester films. The hygrothermal aging resistance of a typical biodegradable poly(lactic acid)/poly(butylene adipate-co-terephthalate) film, enhanced with an interfacial cross-linker to repair interface defects, has been systematically investigated. Toughness indicators, such as elongation at break, toughness, and crack propagation velocity, are sensitive to the hygrothermal aging kinetics of the films, while strength indicators, like tensile strength and Young’s modulus, show minimal sensitivity to aging. The interfacial cross-linker effectively delays the initial hydrolysis and significantly inhibits the deterioration of toughness in polyester films, resulting in a 3-fold increase in failure time under aging conditions. The grafted copolymers formed at the phase interfaces provide enhanced resistance to water molecule erosion, thereby delaying the hydrolysis process. Additionally, the deterioration of mechanical properties after hygrothermal aging is primarily attributed to the disruption of chain entanglement networks, which impairs stress transfer and leads to localized stress concentration. This work introduces a promising and scalable method for manufacturing antiaging biodegradable polyester films.