Improved Flame Resistance of Cotton/Polyester Fleece with Phosphorous-Based Polycarboxylic Acids

Authors: Blanchard, Eugene; Graves, Elena

Submitted to: American Association of Textile Chemists and Colorists Review
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2004
Publication Date: 2/1/2005
Citation: Blanchard, E.J., Graves, E.E. 2005. Improved Flame Resistance of Cotton/Polyester Fleece with Phosphorous-Based Polycarboxylic Acids. American Association of Textile Chemists and Colorists Review. 5(2):2-6.

Interpretive Summary: Cotton-containing textiles are converted to ash upon combustion. The rate of flame spread can be reduced by treatment of the textiles with polycarboxylic acids,.such as citric acid and maleic acid, when less demanding flammability standards are allowable. Of course, rapid flame spread on apparel materials is hazardous to the consumer of such goods and all ordinary apparel fabrics must pass a standard flammability test. The problem is most severe on cotton fleece materials because the material is susceptible to what is called flash burning in which the flame rapidly traverses the surface of the fleece. We have discover that both flash burning and ash formation upon combustion are eliminated by treatment of cotton-containing textiles with polycarboxylic acids that have a phosphorus atom present in the molecule. These fabrics form a char if they do ignite, but the burning occurs without any sign of what is known as glowing combustion. Presently, most cotton-containing fleece apparel fabrics are composed of 50/50 cotton-polyester and these materials pass the mandated flammability test. The new treatment system would allow use of more cotton in the fleece apparel market and it would benefit the consumer by offering more comfortable apparel textiles containing higher percentages of cotton.

Technical Abstract: Phosphorus-based polycarboxylic acid formulations containing sodium phosphinicosuccinic acid or sodium phosphinicobissuccinic acid were used to esterify 80/20 cotton-polyester fleece fabric. These acids are readily prepared as described in the literature by reaction of maleic acid with sodium hypophosphite in aqueous solution. Esterification of cellulose was achieved by reaction of the acid with cotton in the presence of a suitable catalyst. Partial neutralization of the acid allows treatment at pH levels of 3-4.5. This is in contrast to levels of approximately pH 2 that are achievable with the maleic acid/catalyst treatment system because of the buffering action of maleic acid upon addition of sodium carbonate or sodium hydroxide. Good reactivity occurred upon curing at 170-180 °C for 1.5-3 min. Esterification effectiveness was determined by phosphorus analysis. An advantage of the phosphorus-based polycarboxylic acid system is that there is increased char formation upon combustion. In contrast, polycarboxylic acids, such as butanetetracarboxylic acid, citric acid or maleic acid, undergo glowing combustion with subsequent oxidation to ash. Various factors, including effective concentration levels of chemical agents, reaction conditions and thermogravimetric analysis of the substrates are presented.