Team Develops Cheaper, Safer Way To Process Wrinkle-Free Dyed Cotton

October 01, 1998

CHAMPAIGN, Ill. -- Processing wrinkle-free and dye-colored cotton fabric with

formaldehyde-free chemicals in one step -- saving money and reducing environmental hazards -- is potentially in the grasp of industry as a result of experiments at the University of Illinois.

Using butanetetracarboxylic acid (BTCA) and citric acid (CA) in combination with direct dyes, a team led by Mastura Raheel has produced -- in just one step -- high-quality, smooth-drying cotton fabric in colors only slightly lower in quality than those produced using more expensive reactive dyes.

"We're doing all this in one operation," said Raheel, a professor of textiles and clothing. "We are trying to tell the industry to change to an environmentally and human-friendly procedure. While such a changeover might be expensive, our method actually dilutes the cost by mixing expensive components, such as BTCA, with cheaper ones, like citric acid, and by adding the dyeing step, using cheaper direct dyes that work well with BTCA and CA, into the same process."

Since the 1960s, the production of wrinkle-free fabric has relied on formaldehyde-containing chemicals -- since found to be potentially carcinogenic -- as finishing agents to assure smoothness and softness. The fabrics are colored with reactive dyes prior to wrinkle-free treatment to meet consumers' demands. The process allows formaldehyde release during the finishing operation and dye-filled waste to spill into the environment, and results in clothing that may cause allergic reactions.

In the August issue of the Textile Research Journal, Raheel and graduate student Chen Guo reported that BTCA replaces formaldehyde-containing chemicals effectively, and that a one-to-one ratio of BTCA to CA produced smooth cotton fabrics equal to those produced by using 100 percent BTCA. Using CA alone produced an off-color on white cotton and lower durable-press qualities.

A challenge to industry has been to find a substitute for formaldehyde-type agents, which have been successful as cross-linking (durable-press or wrinkle-free) agents for cotton fabrics. BTCA and CA are polycarboxylic acids; both are considered safe. In fact, CA is a component of citrus fruits. The researchers used cheaper direct dyes because other research has shown that reactive dyes are not compatible with BTCA.

"The traditional two-step method gives you better color effects and better depth, but we have achieved results that are almost comparable in a single step," she said. "These results are very encouraging. The color aspect of one step is not excellent, but most consumers would never be able to see the difference. The quality difference is at a technical level, not at the level of human perception."Raheel not only is recommending single-step processing, she also has been pushing for the reuse of dye. In a paper published in the July-December 1997 issue of the European journal Boletin Intexter, distributed this summer, she and U. of I. colleague Paula J. Edgcomb reported that spent dye could be reconstituted and reused with excellent results up to four times.


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