Hydrolytic Degradation of PHB /Amorphous PLA Nanocomposites Containing Chitosan Nanoparticles at Elevated Temperature Under Different pH Conditions

ABSTRACT Hydrolytic degradation of biodegradable polyesters is governed by coupled effects of formulation, morphology, and environmental conditions. Here, PHB/amorphous PLA (PHB/PLA‐AMP, 70/30, w/w) blend films and corresponding nanocomposites containing 1–5 phr chitosan nanoparticles (CNPs) were investigated during accelerated hydrolytic aging at 70°C under acidic, neutral, and alkaline conditions. The degradation response depended strongly on pH and CNP loading, with alkaline exposure generally producing faster gravimetric changes and more pronounced surface deterioration. SEM and CLSM revealed pH‐dependent cracking, localized erosion, and substantial changes in surface topography. AFM also revealed nanoscale surface heterogeneity after the incorporation of CNPs. The thermal response changed as well. DSC showed that hydrolysis changed the crystallization behavior of the PHB‐rich phase. TGA/DTG revealed that the main decomposition temperatures of PHB shifted much more than those of the composite that contains CNP. In summary, these findings show that both the pH level and the CNP loading influence the behavior of PHB/PLA‐AMP nanocomposites when they are subjected to accelerated aging conditions at elevated temperature.