Metallic ferrites as flame retardants and smoke suppressants in flexible poly(vinyl chloride)

Abstract

Two metallic ferrites LaFeO3 and BiFeO3 were successfully synthesized and compared with ZnFe2O4 used as flame retardants and smoke suppressants for flexible poly(vinyl chloride) (PVC). The flame-retardant and smoke-suppressant properties of flame-retarded PVC were evaluated using the limiting oxygen index, smoke density rating, and cone calorimeter tests. The results indicate that BiFeO3 is an excellent flame retardant and smoke suppressant for flexible PVC. Under 30 kW m−2 radiation, the peak value of heat release rate of 20 phr PVC/BiFeO3 was reduced by 44.8 % as compared to neat PVC, and the total smoke produced and average specific extinction area of 20 phr PVC/BiFeO3 were reduced by 54.8 and 52.3 %, respectively. The char residues of the PVC samples were analyzed by SEM and Raman spectra, which suggested the incorporation of ferrites can induce the formation of char layer. This effect combined with the gaseous phase effect of BiFeO3, and hence PVC/BiFeO3 has the best flame-retardant and smoke-suppressant properties.