Investigation of Nigerian kaolinite clays as additives in fire retardant formulations

Abstract

In this work, kaolin clay from two deposits were characterized for material properties using X-ray diffraction analysis, X-ray florescence analysis, thermogravimetric analysis, scanning electron microscopy and fourier transform infra-red spectroscopy, in order to determine their suitability as additives in intumescing paints. Results indicated that compared to Kankara clay, Darazo clay has more crystalline kaolinite. Based on this, Darazo clay appeared more thermally stable, releasing less water of dehydroxylation.  Kankara clay appeared less thermally stable producing consistent endothermic reaction that continuously drew heat away from the wood surface, creating a thermal plateau. The clays appeared to have no effect on the intumescent action. However, their high residual masses of over 90% reduced the total amount of fuel available at the flame front, thereby reducing flammability. At the end of the 10 minutes fire test, and using 11 wt% addition of both Kankara and Darazo clays, the reduction in backside temperature for Kankara is 13.6% while that of Darazo is 7.7%. The hybrid formulation gave the highest cooling effect at 20.56% temperature reduction compared to the control. All the coated boards recorded lower percent mass loss compared to the uncoated wood. Therefore, Nigerian kaolins have potential to serve as additives in fire retardant paints.