Study on flame‐retardancy and thermal degradation behaviors of intumescent flame‐retardant polylactide systems

Two intumescent flame‐retardant (IFR) additives, IFR‐I and IFR‐II, were synthesized and their structure was confirmed by Fourier transform infrared spectroscopy and nuclear magnetic resonance. Polylactide (PLA) was modified by the two IFRs to obtain flame‐retardant composites. The flammability of the PLA/IFR composites was characterized by the vertical burning test UL‐94 and limiting oxygen index. The limiting oxygen index values of the PLA composites increased with increase of IFR content. The PLA composite with 20 wt% IFR‐I could pass the UL‐94 V0 rating, while the composite with 30 wt% IFR‐II could not. The results of pyrolysis combustion flow calorimetry showed that the heat release capacity of PLA composites with 30 wt% IFR‐I decreased 43.1% compared with that of pure PLA. The thermal degradation and gas products of PLA/IFR‐I systems were monitored by thermogravimetric analysis and thermogravimetric analysis infrared spectrometry. Scanning electron microscopy was used to investigate the surface morphology of the char residue.