Synergistic flame-retardant effect between calcium hydroxide and zinc borate in ethylene-vinyl acetate copolymer (EVA)

In this study, we developed a simple, fast and low-cost method for the preparation of lamellar calcium hydroxide particles (Ceg-Ca(OH)2) from chicken eggshell (Ceg) waste. The flame-retardant effect of these particles has been evaluated into ethylene vinyl acetate copolymers (EVA) alone or in combination with zinc borate (ZnB). The incorporation of lamellar calcium hydroxide allows an important reduction of PHRR due to the formation of a cohesive mineral residue. Moreover, its combination with zinc borate enables for further reduction of peak of heat release rate (PHRR) and for an important increase of the cohesion of the mineral residue. XRD analysis of the structure of the residue formed during thermal decomposition has revealed the formation of calcium borate (B2Ca3O6). This latter is deemed responsible of the strong improvement of the residue cohesion.