Ground banana peel combined with phytic acid improves fire performance of poly lactic acid. The banana peel powder was reacted with 3-aminopropyltriethoxysilane, then with phytic acid (a bio-sourced molecule rich in phosphorus) and ammonia. 15% loading of the resulting PA-B (phytic acid – banana) in PLA (poly lactic acid) increased the LOI (limiting oxygen index) of PLA from 21% to 38%. Neat PLA burns rapidly, with considerable burning drips and does not self-extinguish. With 15% PA-B is immediately self-extinguishing and achieves UL94-V0 @ 3 mm. The flame retardant mechanism is identified as pyrolysis of the banana peel materials by phosphoric acid to generate dense char (11% char by weight @ 550°C with 15% PA-B), release of inert gases (ammonia, water) and gas phase action of the PO. radical.
“Eco-friendly flame retardant poly(lactic acid) composites based on banana peel powders and phytic acid: flame retardancy and thermal property”, F-b. Kong et al., J. Polymer Research (2020) 27: 204 https://doi.org/10.1007/s10965-020-02176-4