Preparation of 4-formylphenylboronic modified chitosan and its effects on the flame retardancy of poly(lactic acid)

A boron-based biological flame retardant phenylboronic acid functionalized chitosan (B-CH) was prepared by reacting chitosan (CH) with 4-formylphenylboronic acids. The structure characterization was carried out by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis. B-CH was added into polylactic acid (PLA) by the melt blending method to improve the fire performance of the composite. The results showed that the peak heat release rate (PHRR) of PLA-7% B-CH decreased to 432 kW·m−2 from 564 kW·m−2 of control PLA. The limiting oxygen index (LOI) was increased from 19.1% to 26.2%, and the vertical burning test (UL-94) could reach a V-0 rating. The B-CH participated in the char formation process, which could generate a continuous compact char layer during the combustion to effectively protect the PLA matrix. This work provided an effective strategy to develop environmental friendly flame retardant PLA composites.