Flame‐Retarded Poly (Lactic Acid) Containing Phosphating Chitosan

ABSTRACT Poly (lactic acid) (PLA) is a promising thermoplastic aliphatic polyester to replace petroleum‐based polymers in many fields. However, its flammability has limited its application in areas where fire safety is crucial. Chitosan (CS) is a type of natural alkaline polysaccharide with abundant content and good biocompatibility. In this study, a bio‐based flame‐retardant phosphating chitosan (PCS) was prepared and the effects of PCS on the flammability, mechanical and thermal properties of PLA were evaluated. The limiting oxygen index (LOI) of PLA/PCS blend containing 9 wt% PCS reached 28.9% which was relatively higher than LOI of pure PLA of 20% and passed UL‐94 V‐0 rating. PCS accelerated the carbonization of PLA matrix, and increased the char residue at 800°C. The combustion process was further investigated by cone calorimeter test, and the peak heat release rate and total heat release were significantly decreased. X‐ray photoelectron spectrometer and thermogravimetric‐infrared analysis were used to analyze the composition of char residue and pyrolysis products, which further confirmed that the flame‐retardant mechanism of PCS was the combination of condensed phase and gas phase. However, the mechanical properties of PLA/PCS blend inevitably decreased with increasing of PCS content.