Synergy effect between quaternary phosphonium ionic liquid and ammonium polyphosphate toward flame retardant PLA with improved toughness. (15th September 2020) - Jia, Yun-Wan
Abstract: The development of poly(lactic acid) (PLA) composites having flame retardancy, tensile toughness and transparency is the state-of-the-art, which requires meticulous selection and combination of additives. To achieve this goal, an ionic liquid (IL) tetrabutylphosphonium tetrafluoroborate is synthesized and used as a synergist for ammonium polyphosphate (APP). Due to the high synergistic effect between them, only 1.5 wt% IL and 1.5 wt% APP (total amount of 3 wt%) can endow PLA with fire safety, i.e. limiting oxygen index (LOI) of 27.2, UL 94 V-0 rating and low heat release rate of 290 kW m − 2 . Besides, the elongation at break of PLA containing 3 wt% IL/APP increases from 8.5% of PLA to 204.6%. Meanwhile, the incorporation of IL/APP has tiny impact on the transparency of PLA. The PLA/IL/APP possessing toughness and flame retardancy shows great potentials in the fields of packaging, automotive and electronic and electric industry in the future. Graphical abstract: Image 1 Highlights: A novel ionic liquid (IL) tetrabutylphosphonium tetrafluoroborate is synthesized. [TBP][BF4 ] has excellent synergistic effect with APP. IL/APP endows PLA with excellent fire safety. IL/APP enhances the tensile toughness and crystallinity of PLA. Flame-retardant PLA maintains its transparency.