A PIN FR made wholly from plant-origin materials, in water reaction, was successfully tested in the biodegradable, bio-based polymer PBS. Phytic acid, plants’ natural phosphorus storage molecule, was reacted in aqueous solution with guanosine, a purine nucleoside molecule extracted from plants, to produce a bio-sourced phosphorus and nitrogen containing PIN flame retardant (PA-GU). This was tested at 0 – 30 % loading in PBS poly(butylene succinate), a biodegradable polymer derived from succinic acid, which can be sourced from plants. 10% PA-GU achieved UL94-V2 (3 mm). 30% PA-GU increased LOI (limiting oxygen index) of PBS by over 40% and reduced peak heat release rate by c. 75%. The PA-GU PIN flame retardant acts by generating char (phosphorus) and intumescence (gas release, nitrogen) with the guanosine carbon ring cross-linking the char, resulting in a continuous expanded char layer protecting the polymer surface.
“A fully bio-based intumescent flame retardant for poly(butylene succinate)”, S. Chen et al., Materials Chemistry and Physics 252 (2020) 123222 https://doi.org/10.1016/j.matchemphys.2020.123222