1989 Volume 38 Issue 427 Pages 444-450
The effect of fiber content on the fundamental properties of heat insulators in the vermiculite-fibriform material-phosphate system was investigated by measuring their apparent porosity, compressive strength and thermal conductivity. The granular aggregates used were the raw vermiculite from Fukushima Prefecture, Japan and Palaboroa area, N.E. Transvall, S. Africa, and the fibrous aggregate used were the amosite asbestos from Lydenburg area, N.E. Transvall, S. Africa, commercial rock wool and fiber glass. The bonding material of aggregates was sodium metaphosphate, and magnesium dihydrogen phosphate was mixed as the additive.
A remarkable increase in compressive strength was observed when a small quantity of amosite asbestos or rock woll was added to the vermiculite-sodium metaphosphate system. This was attributed to the formation of bridge bonds due to the reactions of magnesium oxide component in vermiculite and amosite asbestos or rock wool with sodium metaphosphate. This was explained by the X-ray diffraction evidence that sodium metaphosphate reacted with vermiculite and amosite asbestos or rock wool. Scarce increase in compressive strength was observed when a small quantity of fiber glass was added to the vermiculite-sodium metaphosphate system. This was explained by the X-ray diffraction evidence that sodium metaphosphate did not react with fiber glass.
The thermal conductivity was decreased when a proper quantity of fibriform material was added to the vermiculite-phosphate system. This corresponded to the apparent porosity increase caused by the mixing of fibriform and granular aggregates. On the other hand, the thermal conductivity was decreased when a proper quantity of magnesium dihydrogen phosphate was added to the vermiculite-fibriform material-sodium metaphosphate system. This was attributed to the porosity increase due to the dehydration reaction of the magnesium dihydrogen phosphate on firing.
