A Comparative Study on the In Vitro Degradation of PLA Processed by FFF and Film Extrusion

Abstract

Processing methods strongly influence the degradation behaviour of semi-crystalline polylactic acid (PLA) by affecting its molecular orientation, crystallinity, and micro-and macrostructural features. In our previous study, we presented the changes in the properties of the electrospun PLA fibers during in vitro degradation. Building on these findings, this study compares the degradation of PLA specimens prepared using two bulk processing methods: (i) fused filament fabrication (FFF) 3D printing and (ii) film extrusion. Specimens were incubated in phosphate-buffered saline (pH 7.4) at 37 °C for 1, 3, 7, 28, and 56 days. At each time point, degradation was assessed by tensile testing, differential scanning calorimetry, and weight retention analysis. PLA films exhibited an initial decrease in Young’s modulus, followed by a temporary increase and subsequent decline, whereas FFF specimens maintained mechanical stability for several days before a gradual deterioration. Both specimens showed reduced crystallinity over time, with FFF samples becoming fully amorphous by day 56. Minimal weight change (<1%) indicated that degradation proceeded primarily through structural and morphological changes rather than bulk erosion. Overall, 3D-printed PLA exhibited more stable mechanical properties than extruded PLA films. These findings highlight the significant impact of the processing route on PLA degradation, guiding the optimization of PLA performance in biomedical, packaging, and sustainable material applications.