Flame Retardants on fabric can be applied through conventional padding, padding with multiple dips and nips. If followed by 30 to 60 seconds dwell, it gives good results. The pH of the pad bath is optimally kept at approximately 5.0. The amount of flame retardant required depends primarily on the fabric type, application conditions, and test criteria required to be met with. Screening experiments should be conducted to determine the minimum application level for a fabric.
One of the most common processes for applying Flame Retardants on cotton fabrics is the "Precondensate"/NH3 process. One of several phosphoniums "precondensates" is applied after which the fabric is cured with ammonia. Then it is oxidized with hydrogen peroxide. Precondensate is the Tetrakis-hydroxymethyl phosphonium salt pre-reacted with urea or another nitrogenous material. The amount of anhydrous sodium acetate is approximately 4% of the amount of precondensate used. Some precondensates are formulated along with the sodium acetate. Softeners are also added along with precondensates. A critical factor in the successful application of precondensate/NH3 flame retardant is the control of fabric moisture before ammoniation. Generally, moisture levels between 10% and 20% give good results.