Flame retardancy and thermal and mechanical properties of ternary composites comprising polylactic acid, polyethylene glycol, and bamboo fiber

A ternary composite composed of polylactic acid (PLA), polyethylene glyco (PEG)l, and bamboo fiber (BF) at a weight ratio of 70:10:20 was prepared using a twin-screw extruder, incorporating aluminum diethylphosphinate (ADP) and melamine cyanurate (MCA). Specifically, formulations containing 30 parts ADP alone, 10 parts ADP and 10 parts MCA, or 10 parts ADP and 15 parts MCA improved the UL94 rating from V2 to V0. The corresponding values of limiting oxygen index (LOI) were 29.3 %, 25.5 %, and 26.9 %, respectively. The combination of ADP and MCA exhibited a synergistic effect on flame retardant modification of PLA/PEG/BF. Furthermore, both ADP and MCA altered the thermal behavior of the composite; MCA alone increased the melting temperature (Tm) but decreased the crystallization temperature (Tc), whereas ADP increased both Tm and Tc. The crystallization of PLA in the composite showed coexistence of two-dimensional and three-dimensional growth modes after incorporation of MCA and ADP, although their effects on the rate of PLA crystal growth differed. Composites with 30 parts ADP alone and 10 parts ADP and 10 parts MCA loading demonstrated high mass retention rates at 800 degrees C.