Simultaneous fire safety enhancement and mechanical reinforcement of poly (lactic acid) biocomposites with hexaphenyl (nitrilotris(ethane-2,1-diyl))tris (phosphoramidate)

Poly(lactic acid) (PIA) is an important bioplastic polymer with wide engineering applications, but has relatively low tensile strength and high susceptibility to flames. This manuscript reports the synthesis of a new cyclophosphorus-nitrogen flame retardant (FR) - hexaphenyl (nitrilotris(ethane-2,1-diyl))tris(phosphoramidate) (HNETP) for concurrent FR and tensile strength enhancement. H-1, C-13 Nuclear Magnetic Resonance and Fourier Transform Infra-red spectra showed that HNETP was successfully synthesized. The FR properties of PLA/HNETP composites were investigated, and the peak heat release rate (PHRR) reduced by (similar to) 51.3%, total heat released (THR) (similar to) 43.1%, and carbon monoxide (CO) production by (similar to) 46.5% with 3 wt% HNETP loading. The fire performance index increased by (similar to) 65.8%, while the fire growth index decreased by (similar to) 56.7%. The tensile strength and the Young's Modulus improved to (similar to) 67.4 and (similar to )87.8% respectively. A significant increase in limiting oxygen index (LOD (32.5%) was attained with a V-0 rating in the vertical burning test. TG-IR study showed considerable reduction in pyrolysis gaseous products by the PLA/HNETP composites compared to PLA. Insignificant changes were observed in the glass transition and the melting temperature of PLA and PLA/HNETP biocomposites.