Comparison of DMDHEU and melamine-formaldehyde as the binding agents for a hydroxy-functional organophosphorus flame retarding agent on cotton

It is necessary to use a crosslinking agent to bond a flame-retarding hydroxy-functional organophosphorus oligomer (FR) to cotton so that the flame resistance of the treated cotton fabric can be durable to multiple home-laundering. Both dimethyloldihydroxyethyleneurea (DMDHEU) and melamine-formaldehyde (M-F) have been used as the binding agents between FR and cotton. The vertical flammability, limiting oxygen index (LOI) and phosphorus content after different numbers of laundering cycles as well as the wrinkle resistance and tensile strength of the cotton fabric treated with FR/DMDHEU and FR/M-F was investigated and compared in this research. We found that DMDHEU is more effective for crosslinking cotton cellulose and for crosslinking between FR and cotton than M-F. We also found that the bonding formed by DMDHEU between cotton and FR is more durable to multiple laundering cycles than that formed by M-F. M-F is a more effective nitrogen provider than DMDHEU to enhance the flame retarding performance of the treated cotton fabric through phosphorus-nitrogen synergism, therefore the presence of M-F in the flame retardant finishing system significantly increases the flame resistance of the treated fabric. DMDHEU, as an effective crosslinking agent for cotton, causes more fabric strength loss than M-F.