Use of inorganic tin compounds as fire retardants in polyurethanes

Abstract

This thesis investigated the effectiveness of inorganic tin compounds-zinc hydroxystannate (ZnSn (OH)₆), zinc stannate (ZnSno₃) and hydroromarchite (Sn₃O₂ (OH)₃) as fire retardants in flexible and rigid polyurethanes. Fire retardant properties of inorganic tin compounds on flexible and rigid polyurethanes were studied by measuring the LOI values and physical properties. It was found that, increasing of metal stannate contents gave reduction in flammability but increased stiffness. In addition, the zinc hydroxystannate could retard the fire better than zinc stannate and hydroromarchite. When the 10% pbw. of tin compounds were employed, the LOI values of zinc hydroxystannate, zinc stannate and hydroromarchite were 23%, 20% and 20% respectively, The tensile strength and modulus of tin compound-added polyurethane were not significant difference from the control. The thermal degradation study and analysis of Sn, both before and after burning, gave the evidence that these inorganic tin compounds behaved as condensed phase fire retardants. However, the mechanism of fire retardant of the tin compounds in polyurethane foams was not clearly understood.