One-pot scalable fabrication of an oligomeric phosphoramide towards high-performance flame retardant polylactic acid with a submicron-grained structure

Last years have witnessed great advances in minimizing the flammability of the polylactic acid (PLA) bioplastic. Unfortunately, to date there remains an urgent lack of a facile strategy to develop highly effective flame retardants for PLA. Herein, we report one-pot scalable fabrication of an oligomeric phosphoramide, phenyl phosphonic piperazine (PPP), via a one-step condensation polymerization. PPP can finely disperse within the PLA matrix showing a submicron-grained structure with a domain size of 100-300 nm. The addition of 3 wt% PPP increases the limiting oxygen index (LOI) of PLA to 32.5 vol%, and a V-0 rating is achieved. Such high flame retardancy is mainly attributed to the free radical quenching, gas dilution and the thermal barrier action of the char layer. Moreover, the PLA/3%PPP composite retains a tensile strength of 55.4 MPa. This work provides a facile and scalable approach to preparing high-performance flame retardant PLA materials.