Synthesis of C o ₃ ( HPO ₄ ) ₂ ( OH ) ₂ nanosheets and its synergistic effect with intumescent flame retardants in ethylene‐vinyl acetate copolymer

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In the present work, Co 3 (HPO 4 ) 2 (OH) 2 nanosheets were synthesized by hydrothermal method, and its structure was characterized by X‐ray diffraction and transmission electron microscopy. Then it was used as a synergistic agent with intumescent flame retardant (IFR) in ethylene‐vinyl acetate (EVA) copolymer. Thermogravimetric analysis data indicated that the addition of Co 3 (HPO 4 ) 2 (OH) 2 nanosheets into the EVA/IFR composites could increase the char yields. Cone calorimeter results revealed that Co 3 (HPO 4 ) 2 (OH) 2 in combination with IFR obviously changed the thermal decomposition behavior of EVA and formed a protective char layer on the surface of the composites, consequently leading to effective reduction in the flammability parameters, such as the heat release rate, total heat release. With the addition of 1 wt% Co 3 (HPO 4 ) 2 (OH) 2 and 34 wt% IFR, the LOI value increased to 26.5%, and the system could reach V‐0 rating. Laser Raman spectra of the residual char showed that the more graphitic char was formed with increasing the loading of Co 3 (HPO 4 ) 2 (OH) 2 . Scanning electron microscopy results demonstrated that the incorporation of Co 3 (HPO 4 ) 2 (OH) 2 promoted the EVA/IFR system to form a dense and continuous char layer. POLYM. COMPOS., 39:238–246, 2018.