Temporal evolution of structure property relationship for UV+RH artificially weathered material extrusion additive manufactured PLA

Abstract

This study addresses the underreported temporal evolution of weathering on material extrusion additive-manufactured (MEX-AM) polylactic acid (PLA). Overcoming the limitation of arbitrary exposure durations in existing literature, a time-dependent investigation was conducted on MEX-PLA samples subjected to prolonged artificial weathering for up to 2000 h using a UV-B equipped accelerated weathering chamber with controlled relative humidity. The changes in mechanical, chemical and thermal properties were analysed at 200-hour intervals. The results revealed a time-dependent degradation mechanism characterised by β-chain scission. FTIR analysis confirmed the formation of C = C groups and the progressive loss of H groups, indicating substantial material degradation. Furthermore, DSC and XRD data demonstrated a progressive increase in crystallinity with prolonged exposure, leading to a significant reduction in tensile strength. At the same time, the tensile modulus remained relatively stable for MEX-AM PLA.