Effect of bauxite residue loading on heat shielding performance of an ammonium polyphosphate based epoxy intumescent system

Bauxite residue (BR) is the aluminosilicate waste generated by the alumina industry. Its disposal has become a global industrial problem. Preliminary study has recognized its potential as synergistic filler in intumescent system. In this work, the effect of percent weight of the residue on the heat shielding performance of the system was investigated. Different formulations were prepared by varying filler loading from 0 to 5. Performance characterization of the coatings were done by using Furnace test to determine the char expansion at 500 °C and Bunsen burner test to determine insulative capacity at 900 ± 100 °C. Thermogravimetric analysis was used as analytical tool. The presence of hydrated minerals in BR and early dehydroxylation of layered silicates were found to have a marked effect on heat shielding and flame spread. The effect of dehydroxylation appeared optimal at 2 BR influencing the melt rheology, improving insulative efficiency and reducing the flame spread. A steel back temperature of 172 °C was recorded compared to that of the unfilled with 267 °C. Excessive dehydroxylation at 4 BR led to high mass loss and early oxidation of char. The combined endothermic action of the hydrates and calcites and physical thermal barrier of the ceramic metal phosphates resulted in improved heat shielding performance and flame retardation of the BR-filled epoxy intumescent systems. ©2006-2016 Asian Research Publishing Network (ARPN).