A novel highly-efficient bio-based fire retardant for poly (lactic acid): Synthesis, preparation, property and mechanism

In this work, the highly-efficient multifunctional bio-based fire retardant phenylphosphonic difurfurylamine (PPDF) was prepared successfully for poly(lactic acid) using furfurylamine and phenylphosphonic dichloride. Moreover, the structure of PPDF was analyzed by NMR, FTIR and MS. The fire safety, thermal, crystallization, rheological and mechanical properties of PLA/PPDF compounds were systematically tested by LOI, UL94, cone calorimeter test, TGA, DSC, polarizing optical microscope, rheometer, DMA and tensile properties. Surprisingly, only a very small loading of 0.8 wt% loading of bio-fire retardant PPDF could increase the LOI value of PLA from 19.0 % to 30.0 % and achieve V-0 rating in UL-94 vertical burning test. Moreover, PPDF not only reduced the molecular entanglement and viscosity of PLA, but also acted as a nucleating agent to increase crystallinity and crystallization rate of PLA matrix. More importantly, in the gas phase phosphorus, the PLA/PPDF compounds based on highly reactive benzene, phosphorus, phosphooxygen and phosphooxygen benzene radicals from the pyrolysis of PPDF had a highly-efficient fire safety. In the condensed phase, a relative stable residual char layer played a secondary role in the barrier. Thus, the total heat release and ignition time of PLA/PPDF compounds were evidently declined by 8.3 % and 10 s with only 0.8 wt% of PPDF loading.