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Performance of FR bonding system consisting of dimethylol(N-hydroxymethyl-carbamoylethyl) phosphonate (MDPA) and citric acid (CA)

One of the most effective flame retardants for durable FR finishing of cotton is dimethylol (N-hydroxymethyl-carbamoylethyl) phosphonate (MDPA), better known under the trade name Pyrovatex CP New. MDPA is a phosphorus-based flame retardant that acts in the condensed phase and is particularly adequate for treatment of polymers containing oxygen such as cellulose. MDPA can react with cellulose under acid-catalyzed conditions without crosslinking whereas the phosphonopropionamide group is not efficiently fixed. In the research, performed by C.Q.Yang it was determined that approximately 52% of MDPA is able to directly bond to cotton, without other additives. For the increase of its fixation level an amino resin, such as trimethylolmelamine or DMDHEU is normally used. The usage of such nitrogen-containing additive increases the percentage of MDPA bound to cotton while simultaneously providing synergistic effect of nitrogen with phosphorous, enhancing the flame retardance performance. The usage of both compounds leads to the emission of high levels of formaldehyde, so much effort has been done to develop new nonformaldehyde crosslinking agents for cotton. Another research work has been dedicated to the substitution of conventional trimethylolmelamine or DMDHEU binders with the more environmentally friendly ones. Polycarboxylic acids were used as such alternative binders in FR finishing of cotton, wood or paper cellulose. They have already proven to be effective crosslinking agents for Durable Press finishing of cotton as a substitute of the formaldehyde derivatives and many recent studies were focused on their possible usage for other crosslinking purposes. Citric acid is capable to react both with its carboxyl groups, through the formation of anhydrides, so as with its -hydroxyl group. It can esterifies both ; cellulose or MDPA hydroxyls and its application as a formaldehyde-free binder in the flame retardant finishing system with MDPA agent was studied in this research.

MDPA; CA; LOI; Flame Retardant

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