Effect of Rare Earth Hypophosphite Salts on the Fire Performance of Biobased Polylactide Composites

In this work, two kinds of rare earth hypophosphites (REHP), lanthanum hypophosphite (LaHP) and cerium hypophosphite (CeHP), were synthesized and characterized. Subsequently, LaHP and CeHP were added into polylactide to improve its flame retardant properties. Thermal gravimetric analysis was employed to investigate the thermal decomposition behavior of REHP and flame retardant polylactide composites (FR-PLA). The fire performance evaluated by microscale combustion calorimetry and cone calorimeter clearly demonstrated that the addition of LaHP and CeHP resulted in significant reduction of the heat release rate, low total heat release, and compact intumescent char layer. Thermogravimetric analysis–infrared spectrometry testing indicated that the addition of REHP significantly decreased the yields of pyrolysis products. Furthermore, the crystallization behaviors of FR-PLA composites were investigated by differential scanning calorimetry. The char residue of FR-PLA composites after cone calorimeter testing were also be investigated by scanning electron microscope, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy.