The Hydrolytic Behavior of Poly(Lactic Acid)/Polystyrene‐ Grafted‐Hectorite Nanocomposite Films and Its Regulatory Mechanism on Microplastics

ABSTRACT This study investigated the degradation behavior of poly(lactic acid) (PLA) films and PLA/polystyrene‐grafted hectorite (PLA/Hec‐g@PS) nanocomposite films in aqueous solutions of varying pH (neutral, acidic, alkaline). The results demonstrated that water molecules play a critical role in the degradation process. Compared to pristine PLA films, the Hec‐g@PS nanocomposite films significantly enhanced the hydrolytic resistance of PLA, effectively mitigating surface damage and crack formation. Analysis using a first‐order kinetic model revealed that the degradation reaction rate constants for PLA/Hec‐g@PS films were consistently lower than those for pristine PLA films across all tested environments (neutral, acidic, alkaline). This performance improvement is attributed to the incorporation of Hec‐g@PS, which increases the crystalline regions within PLA, reduces the exposure of ester groups in the amorphous domains, and restricts water molecule diffusion due to its hydrophobic nature, thereby synergistically retarding the hydrolysis process. Further research focused on the PLA/Hec‐g@PS nanocomposite films elucidated the mechanism by which Hec‐g@PS influences PLA microplastic (PLA‐MPs) generation: Hec‐g@PS effectively reduces the quantity of PLA‐MPs formed during degradation and inhibits microplastic shedding. Mechanistic studies verified that Hec‐g@PS optimizes the arrangement of PLA chain ends through intermolecular interactions, resulting in a denser structure that lowers the potential for microplastic release during degradation.