Environmental degradation and durability of bulk 3D-printed parts from biodegradable polyester blends of PBS, PLA, and PHB in seawater†

Abstract

The environmental degradation of biodegradable polyester parts prepared via fused filament fabrication (FFF) from poly(butylene succinate) (PBS)/poly(lactic acid) (PLA) and PBS/poly(hydroxybutyrate) (PHB) blends (5/5 and 7/3 w/w) was systematically studied in static artificial seawater over six months. In contrast to typical thin-film degradation studies, bulk specimens provide realistic insights into the degradation behavior of thicker polymer products encountered in practical marine applications. 3D-printed dumbbell specimens fabricated with concentric and rectilinear infill patterns were investigated to tackle this issue and respond to emerging additive manufacturing trends. Changes in mechanical performance were significant, with the PBS/PHB (5/5) blend showing a pronounced 3.3-fold reduction in ultimate strength and a 2.5-fold reduction in elastic modulus. A three-stage sorption model was applied, quantifying water diffusion, hydrolytic degradation, and leaching of polymer components. Morphological examinations using scanning electron microscopy and energy-dispersive X-ray spectroscopy revealed crystalline salt deposits forming preferentially at interlayer interfaces, contributing to accelerated structural deterioration. Differential scanning calorimetry further showed shifts in crystallization temperature and crystallinity, underscoring alterations in polymer structure due to degradation. These results demonstrate that bulk part dimensions and 3D printing parameters critically influence degradation pathways, emphasizing the necessity of bulk-scale studies to predict real-world degradation behavior in marine environments accurately.