Recent advances on the ageing of flame retarded PLA: Effect of UV-light and/or relative humidity

Three different accelerated ageing scenarios were applied on flame retarded polylactic acid (FR-PLA). The influence of (i) Temperature and UV-light exposure (T/UV), (ii) Temperature and relative humidity exposure (T/RH) and (iii) combined Temperature, UV-light and relative humidity (T/UV/RH) exposure on (i) the morphology, (ii) the physico-chemical properties and (iii) the fire performances of FR-PLA were evaluated. The influence of FR fillers (melamine, ammonium polyphosphate and organomodified montmorillonite) as well as the associated mechanisms of degradation (i.e. photo-degradation under T/UV, hydrolysis under T/RH and a combination of both phenomena under T/UV/RH) were explained. The flame retardant properties of FR-PLA before and after ageing were compared using Limiting Oxygen Index (LOI) and Mass Loss Calorimetry (MLC). It was reported that FR-PLA aged under T/UV/RH conditions is more degraded compared to FR-PLA exposed to T/RH or T/UV. Surprisingly, the FR properties are enhanced after ageing, even if the degradation of the samples is observed.