Durable Flame Retardant Cotton Fabric Prepared by Partial Pyrophosphorylation and Metal Complexation

In order to prepare durable flame retardant cotton, mercerized cotton fabric is treated with orthophosphoric acid at 140°C or pyrophosphoric acid at 110°C, followed by metal-complexation. The LOI (limited oxygen index) values of the pyrophosphorylated cotton fabrics are higher than those of orthophosphorylated fabrics; the pyrophosphory lated fabric treated with Ni 2+ has an LOI value of 28, and those treated with Ca2+, Mg 2+, or Zn2+ have a value of 26. The pyrophosphorylated fabric merely rinsed in running tap water has an LOI value of 26. These values are similar to those for cotton fabrics resin-finished with organophosphorus compounds. The LOI values of treated fabrics do not decrease after laundering, in contrast to the behavior of resin-finished fabrics. The pyrophosphorylated sample has a tensile strength, elongation, and hand similar to those of untreated fabrics, and is susceptible to enzymatic hydrolysis to release reducing sugars.