Mechanical Properties and Degrading Behaviors of Aluminum Hypophosphite-Poly(Lactic Acid) (PLA) Nanocomposites

The flame retardancy of poly(lactic acid) (PLA)/aluminum hypophosphite (AHP, phosphorous content = 41.87 wt.%) nanocomposites (PLA/(AHP-x), x = 15%, 20%, 25%; and x denotes the weight percentage content of AHP) was greatly enhanced by melt blending of AHP into PLA through twin-screw extruder and injection-molding process. The UL 94 V-0 flammability rating can be reached for PLA/(AHP-20%) with the LOI value over 28.8. The well dispersion of the AHP in PLA/(AHP-x) was investigated by FT-IR spectra under the line mapping model. Based on TGA results under a non-isothermal condition, the thermal degradation kinetics of PLA/(AHP-x) composites were studied by Kissinger’s, Ozawa’s and Flynn-Wall-Ozawa’s (FWO’s) methods. And those thermal degradation dynamic analyses showed lower activation energy (E_K or E_O) (from 155 to 122 kJ·mol^–1) corresponded to higher content of AHP (from 15 to 25 wt.%) for PLA/(AHP-x) nanocomposites. Kissinger’s, FWO’s and Coast-Redfern’s methods were used to discriminate the kinetic models and kinetic parameters for the thermal degradation of PLA/(AHP-x), which suggested conversion function G (α) = [-ln(1-α)]^2/3 or G (α) = α for the investigated process. The flame retardant PLA nanocomposites obtained in this study will become safety environment-friendly potential candidates in household and automobile engineering with high performance.