The preparation of fully bio-based flame retardant poly(lactic acid) composites containing casein

In this work, a bio-based flame retardant, casein, was incorporated into poly(lactic acid) (PLA) matrix by melt compounding in order to improve the fire resistance and sustain the biodegradable character of PLA simultaneously. The fire performance of PLA composites was evaluated by limiting oxygen index, UL-94 vertical burning, and cone calorimeter tests, respectively. The results indicated that the introduction of 20% casein increased the limiting oxygen index value of PLA composites from 20.0% to 32.2%, upgraded the UL-94 rating from no rating to V-0, and decreased the peak heat release rate from 779 to 639 kW/m(2). The decomposition products of PLA composites were analyzed by Fourier transform infrared, and the morphology of the char after combustion was observed by scanning electron microscopy. It was suggested that casein took effects in both gas phase by releasing non-flammable gases (such as NH3 and H2O) and condensed phase by the formation of protective char layers. However, the presence of casein in PLA induced an unavoidable deterioration in the mechanical performance. (c) 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46599.