Molded environment‐friendly flame‐retardant foaming material with high strength based on corn starch modified by crosslinking and grafting

A flame‐retardant foaming material based on corn starch was prepared by a mold pressing method. The starch was crosslinked using Na 3 [PO 3 ] 3 and became gelatinized. Initiated by (NH 4 ) 2 S 2 O 8 , the starch was grafted with methyl acrylate and vinyl acetate by a free‐radical polymerization. The starch was mixed with the foaming regent composed of NaHCO 3 and azodicarbonamide, and molded at 135 °C and 9 MPa for 10 min. A foaming material with a uniform honeycomb‐like structure and relatively high strength was prepared. Its apparent density, tensile strength, impact strength and elongation were 0.685 g cm −3 , 1.065 kJ m −2 , 3.025 MPa, and 28.8%. It held excellent flame resistance of V‐0 rating. Na 3 (PO 3 ) 3 acted both as crosslinker and flame retardant, which effectively simplified the formula. When the material was burnt, a compact charred crust was formed on its surface, which prevented the permeation of oxygen and the release of combustible organic compounds. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136 , 47193.