Assessment of the protective effect of PMMA on water immersion ageing of flame retarded PLA/PMMA blends

The incorporation of PMMA into phosphorus-containing flame retarded PLA was assessed as a possible strategy to reduce the sensitivity of the material to ageing in water at 70 °C. PLA and PMMA are miscible and the unique glass transition temperature can be easily controlled by a proper amount of PMMA according to Gordon-Taylor equation. Water penetration as well as phosphorus release was reduced when incorporated PMMA amount increased. Consequently, the ability to form char and the fire performances measured in cone calorimeter were further preserved. Nevertheless, an efficient protective effect was only observed when PMMA incorporation allows the glass transition temperature in the blend to increase above the ageing temperature. This is achieved for a weight ratio PMMA/PLA no lower than 1. •Miscible blends PLA/PMMA flame retarded with ammonium polyphosphate and sepiolite were aged in hydrothermal conditions.•The release of APP during ageing leads to an increase of flammability.•This phenomenon can be slowed down when PMMA content is higher than 50 wt%.•The release of APP is mainly monitored by the glass transition temperature controlling by the PMMA/PLA ratio.