Assessing the performance characteristics of aluminum-doped PLA composites after exposure to environmental conditions

This study investigates the impact of salt spray aging (per ASTM B117) on the mechanical, thermal, and morphological properties of aluminum-doped polylactic acid (PLA) composites fabricated using filament fed material extrusion-based additive manufacturing (MEX). Specimens containing 25 wt% Al were subjected to accelerated aging for 2, 4, and 8 weeks. The results indicated a dramatic degradation in mechanical properties after 8 weeks, with the ultimate tensile strength plummeting by approximately 88% (from 30.04 MPa to 3.66 MPa) and elongation at break dropping to 1.8%. Thermal analysis revealed a decrease in glass transition temperature (Tg) from 68.45°C to 67.25°C after 8 weeks, confirming polymer chain scission due to hydrolysis. The onset of thermal degradation also shifted to a lower temperature. Morphological examination via Scanning Electron Microscopy (SEM) unveiled severe interfacial debonding between the PLA matrix and aluminum particles, along with the formation of cracks and salt crystals, providing direct evidence of synergistic hydrolytic and corrosive degradation. In conclusion, the susceptible PLA/Al interface causes catastrophic failure in saline environments, necessitating strategies like coupling agents to ensure durability.