Phosphorylated chitosan-cobalt complex: A novel green flame retardant for polylactic acid

摘要

The exploration of green flame retardants is of great significance for fire safety, ecological environment protection, and resource saving. Herein, a novel phosphorus containing chitosan-cobalt complex (CS-P-Co) was successfully synthesized for the first time and then introduced into polylactic acid matrix. Owning to the formation of cobalt salts, the CS-P-Co exhibits good thermal stability and catalytic char effect. The as-fabricated biodegradable polylactic acid/CS-P-Co composites with small amounts of CS-P-Co ( 4.0wt%) show remarkably improved flame retardancy, such as decreased peak heat release rate and total heat release by 23.0% and 20.0%, respectively. Scanning electron microscopy, Thermogravimetric analysis, and Raman results demonstrate that compact graphitized char layers are formed on the composite surface during combustion, attributed to the catalytic effect of CS-P-Co. The char inhibits diffusion of heat, mass, and oxygen, which plays a key role in the flame retardancy enhancement.