Durable flame retardant cotton fabric prepared by partial pyrophosphorylation and metal complexation

In order to prepare durable flame retardant cotton, mercerized cotton fabri c is treated with orthophosphoric acid at 140 degrees C or pyrophosphoric a cid at 110 degrees C, followed by metal-complexation. The LOI (limited oxyg en index) values of the pyrophosphorylated cotton fabrics are higher than t hose of orthophosphorylated fabrics; the pyrophosphorylated fabric treated with Ni2+ has an LOI value of 28, and those treated with Ca2+, Mg2+ 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 co tton fabrics resin-finished with organophosphorus compounds. The LOI values of treated fabrics do not decrease after laundering, in contrast to the be havior of resin-finished fabrics. The pyrophosphorylated sample has a tensi le strength, elongation, smd hand similar to those of untreated fabrics, an d is susceptible to enzymatic hydrolysis to release reducing sugars.