Statistical analysis of the performance of the flame retardant finishing system consisting of a hydroxy-functional organophosphorus oligomer and the mixture of DMDHEU and melamine–formaldehyde resin

Abstract

In our previous research, we developed flame retarding systems for cotton based on a hydroxy-functional organophosphorus oligomer (FR) and a binder, such as 1,2,3,4-butanetetracarboxylic acid (BTCA), dimethyloldihydroxyethyleneurea (DMDHEU) and melamine–formaldehyde (M–F), which are able to form covalent binding between FR and cotton. In this research, we used a factorial experimental design method to study the performance of the flame retarding system based on FR and the mixture of DMDHEU and M–F. We found that an increase in the DMDHEU/(DMDHEU + M–F) ratio in the mixture increases the amount of FR bound to cotton, increases the laundering durability of FR on cotton, and reduces the fabric tensile strength retention. DMDHEU and M–F also function as nitrogen providers and enhance the flame retarding performance of the treated fabric due to phosphorus–nitrogen synergism. M–F is a more efficient nitrogen provider than DMDHEU. The effect of reduced phosphorus–nitrogen synergism as a result of increasing the relative amount of DMDHEU in the mixture (DMDHEU + M–F) outweighs that of the improved bonding of FR to cotton. An increase in FR concentration in a formula increases the amount of FR bound to cotton, whereas it reduces the percent retention of FR on the fabric and also reduces the fabric strength loss. Desirable performance of treated cotton fabrics can be achieved by adjusting the concentrations of FR and the ratio of the two binders in a formula.