Comparative study on mechanical properties of virgin and recycled polylactic acid aging in natural weathering and seawater environment

The environmental issue derived from petroleum-based plastic has brought wide attention on biodegradable plastic. The enforcement of new regulation on the requirement of environmentally friendly plastics has increased the demand of polylactic acid (PLA). Considering the increasing application of PLA, the accumulation of PLA wastes is also expected to increase. Recycling of PLA wastes is one of the promising alternatives in the minimization and sustainability of resources. However, the properties of the recycled PLA (RPLA) are deteriorated. This work intended to study the mechanical properties degradation of virgin PLA (VPLA) and RPLA aging in natural weathering and seawater environment. The degradation in mechanical properties was analyzed by tensile strength, transverse rupture strength (TRS), impact energy, and hardness. The samples were exposed to natural weathering and seawater environments for 150 days, and the mechanical properties degradation was monitored every 30 days. The results showed that the tensile strength, TRS, impact energy, and hardness properties degraded faster in RPLA than in VPLA. It was also noted that the degradation in tensile strength, TRS, impact energy, and hardness properties was more accelerated in seawater environment than in natural weathering environment, which suggested that hydrolysis degradation was a more predominant phenomenon than thermal degradation. No alteration on the surface and physical morphology was observed on the samples for both VPLA and RPLA in natural weathering and seawater environment, which indicated that the samples had undergone bulk degradation. No significant differences were observed in the thermal stability of VPLA and RPLA after aging in both environments.