Preparation of Polylactide Composite with Excellent Flame Retardance and Improved Mechanical Properties

Abstract

Despite the good biodegradable and mechanical properties, poly(lactic acid) still suffers from a highly inherent flammability, which restricts its applications in the electric and automobile fields. In order to improve the flame retardancy of PLA, in this work, melamine polyphosphate (MPP) and zinc bisdiethylphosphinate (ZnPi) were firstly incorporated into PLA, and the synergistic effect of them on flame retardance of PLA was investigated using limiting oxygen index (LOI), UL-94 vertical measurement, scanning electron microscopy (SEM) and cone calorimeter tests etc. The results showed that PLA composite with 15 wt% of MPP/ZnPi (3:2) had the best flame-retardant efficiency with LOI value of 30.1 and V0 rating in UL-94 tests, which was far better than using MPP or ZnPi alone. What is more, although a wide range of flame retardants have been developed to reduce the flammability, so far, they normally compromise the mechanical properties of PLA. On the premise of maintaining good flame-retardant performance, we improved the toughness of flame-retardant PLA composite, and the impact strength of flame-retardant PLA composite was more than tripled (8.08 kJ/m2) by adding thermoplastic urethanes (TPU). This work offers an innovative method for the design of the unique integration of extraordinary flame retardancy and toughening reinforcement for PLA materials.