Combination Effect of Organically Modified Montmorillonite and Layered Nickel Hydroxide on the Fire Retardancy of Poly(Lactic Acid)

The combination effect of organically modified montmorillonite (OMT) and layered nickel hydroxide (Ni(OH)2) on the fire retardancy of poly(lactic acid) (PLA) was reported. Thermogravimetric analysis and microscale combustion calorimeter were used to evaluate the thermal stability and fire retardancy of the PLA nanocomposites. Direct pyrolysis/mass was employed to investigate the thermal degradation behaviors of the PLA nanocomposites. The char residues of the PLA nanocomposites were characterized by X-ray diffraction and Raman spectroscopy. After the incorporation of OMT and Ni(OH)2 into PLA, the decomposition temperature occurred earlier but improved char residue was obtained. The combination of OMT and Ni(OH)2 led to a significant reduction in the heat release rate and total heat release of PLA as compared to the individual component. The presence of OMT was beneficial for the formation of gas and liquid species from PLA with lower molecular weight. As for the char residues of the PLA nanocomposites, the combination of OMT and Ni(OH)2 contributed to the highest graphitization degree. It was metallic Ni in situ reduced from Ni(OH)2 that acted as the catalytic role of graphitization.