Abstract
Phosphorous, as sodium dihydrogen phosphate, and nitrogen, in the form of a urea–for-maldehyde condensate, were applied to cotton fabric. The flame-retarding character of each treated fabric was assessed by determining the respective limiting oxygen index. Analysis of the results showed that at the lowest levels of applied phosphorous (P = 2%), the presence of nitrogen produced less than an additive combined flame-retarding effect. At higher phosphorous levels, this deviation from additivity increased until at P > 6%, the presence of nitrogen antagonized the flame-retarding effect of the phosphorous. These observations are discussed within the current ideas of nitrogen–phosphorous interaction in flame-retardant systems, for cotton-containing fabrics.