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Title
The superiority of hydrated zinc and nickel versus hydrated sodium sulfate in the flame-retardancy of cellulosic fabrics
Authors
S. M. Mostashari O. Baghi and H. F. Moafi
Received
April 14, 2008
Published
Volume 43 Issue 7-8 July-August
Keywords
sodium sulfate decahydrate, zinc sulfate heptahydrate, nickel sulfate hexahydrate, combustibility,
flame-retardancy, thermogravimetry
Abstract
fabrics, for investigating their effectiveness as flame-retardants. A vertical flame spread test was then
accomplished and the specimens’ degree of resistance to burning was assessed. An efficient quantity of
ZnSO4, expressed in dry salt per 100 g fabric, has been determined over the 11.2-16.3 g range. For NiSO4,
this value was obtained over the 11.8-14.3 g range. In spite of this close resemblance, the incorporation of
Na2SO4 over about 25.2% (almost twice as much as the above-mentioned quantities) showed no trace of
flame-retardancy. Thermogravimetric analyses of both pure cotton and cotton treated with the aforementioned
salts were accomplished, the thermograms being compared and interpreted. The results obtained
for zinc and nickel sulfate suggest that the expulsion of the hydration water present in treated cellulose
occurred well below the desirable range, prior to the thermal degradation of the cotton substrate. However,
the application of sodium sulfate decahydrate to the cotton fabric illustrated an overlapped curve in the
cellulose thermogram. Quite significantly, the loss of hydration water for the last mentioned salt occurred
approximately in the same temperature zone of the thermal decomposition range of the polymer, where it
showed no advantage in imparting flame-retardancy. Meanwhile, the thermograms for hydrated ZnSO4 and
NiSO4 showed mass loss at high temperature, below the above-mentioned zone, which involves the
catalyzation of the substrate thermal degradation; hence, their combustion retardation can be controlled.
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