New Superefficiently Flame-Retardant Bioplastic Poly(lactic acid): Flammability, Thermal Decomposition Behavior, and Tensile Properties

In this study, a superefficiently flame-retardant bioplastic poly­(lactic acid) was developed by incorporating gas–solid biphase flame-retardant <i>N</i>,<i>N</i>′-diallyl-<i>P</i>-phenylphosphonicdiamide (P-AA), into PLA matrix. The flame retardancy of PLA/P-AA was investigated by limiting oxygen index (LOI), vertical burning test (UL94), and cone calorimeter test. Surprisingly, it was noted that only 0.5 wt % loading of P-AA increased LOI value of PLA from 20.5 to 28.4 and passed UL 94 V-0 rating at 3.2 mm thickness. In order to understand the effect of P-AA on the thermal decomposition behavior of PLA, a comprehensive study was investigated in this paper, including (i) adopting modified Coats–Redfern method to study the thermal decomposition kinetics of PLA and PLA/P-AA systems, and (ii) characterizing the evolved gaseous products and the residues in the condensed phase by thermogravimetry linked Fourier transform infrared spectroscopy (TGA–FTIR) and variable temperature Fourier transform infrared spectroscopy (VT-FTIR) techniques, respectively. Moreover, tensile properties of PLA and PLA/P-AA were studied