Disintegration Behavior in Industrial Conditions of Poly(lactic acid)/Poly(hydroxybutyrate-co-valerate) Blends

Abstract

This study provides a comprehensive evaluation of the disintegration kinetics of poly(lactic acid) (PLA)/poly(hydroxybutyrate-co-valerate) (PHBV) blends by exploring the full compositional spectrum (neat polymers and three intermediate ratios), bridging the gap between degradation behavior, the underlying thermal and mechanical properties, and crystallinity. Extrusion and injection molding techniques were used as processing techniques, and they were instrumental in defining the blends’ final properties and microstructural organization. The resulting crystallinity was identified as a primary factor influencing the disintegration behavior, acting in conjunction with the surface-area-to-volume ratio dictated by sample thickness. The results suggest that PHBV negatively affects the fragmentation of the blends, likely due to its inherently high crystallinity and hydrophobicity, potentially assisted by a constrained amorphous fraction that maintains material stiffness near typical industrial composting temperatures. This behavior was consistently observed in both laboratory-scale and pilot-scale disintegration tests. To gain deeper insights into the disintegration mechanisms, scanning electron microscopy was carried out on the surfaces of the degraded samples, revealing morphological changes and degradation patterns correlated with the structural and compositional differences among the materials. Overall, this study highlights the need to correlate morphology and thermal characteristics with processing history and disintegration conditions to accurately assess the disintegration behavior of biodegradable polymer materials.