The intumescent flame‐retardant biocomposites of poly(lactic acid) containing surface‐coated ammonium polyphosphate and distiller's dried grains with solubles (DDGS)

This work aims to develop the poly(lactic acid) (PLA) biocomposites with high flame‐retardant performance, which can be applied in electronic and electrical devices as well as automotive parts. First, an intumescent flame retardant composed of ammonium polyphosphate (APP) as the acid source and the blowing agent, and the distiller's dried grains with solubles (DDGS) as the natural charring agent was designed. The surfaces of DDGS and APP were coated by degradable polymeric flame‐retardant resorcinol di(phenyl phosphate) (RDP), and the coating effects were analyzed. And then the flame‐retardant biocomposites of PLA with RDP‐coated DDGS (C‐DDGS) and RDP‐coated APP (C‐APP) were prepared. The limited oxygen index value of the biocomposites with loading of 15 wt% C‐DDGS and 15 wt% C‐APP reached 32.0%, and UL‐94 V‐0 was attained. The biocomposites also had good mechanical properties and the tensile strength of this sample reached about 57 MPa. Finally, the char residues after burning were analyzed and the flame‐retardant mechanism was discussed.