Search :
Winter 1997

Research Magazine > ARCHIVE > Winter 97 > Article

by Catherine Gianaro 

Ah, the nature of cotton: the soft touch of a fresh bath towel, the comfort of summer sheets, the gentle gauze covering a nasty wound. But sometimes even nature needs a little help. Before it gains its tender qualities, natural cotton must endure harsh chemicals to become absorbent. That's why Ian Hardin is developing an alternative process that will save time, energy and environmental injury.

"Most people look at the stains on clothing and just assume that cotton is naturally absorbent," said Hardin, who heads the textiles, merchandising and interiors department at the University of Georgia. "But if you take cotton from a boll, remove the seeds and put it in water, it won't absorb a drop. It will actually float there for weeks."

Cotton fibers have a waxy outer layer that must be dissolved through a process called "scouring" before liquids, such as dyes, can penetrate. Instead of using chemicals to remove the waxy layer, Hardin turned to enzymes. He experimented with many - most fruitfully with cellulase and pectinase - in sundry combinations. After each attempt, he measured the amount of absorption.

"We need to find the truly optimum approach," he said. The goal is to use the lowest concentration of enzyme for the least amount of time and at the lowest temperature to achieve the desired degree of absorption. These three variables - concentration, time and temperature - are the keys to the solution.

Temperature is a main concern because the chemical scouring process requires high temperatures that demand more energy. "We can do it at a much lower temperature [with enzymes]," Hardin said. "Knowing that, we can project substantial energy savings."

Hardin's method also will cut the processing time by more than 90 percent. "Although it varies with each mill, an hour is not atypical. And we're talking about changing it to a matter of minutes," he said.

However, the new technique will require close management. "If you allow these enzymes to continue working, they'll start eating away at the body of the fiber," he said. "You have to maintain strict control of the process."

Environmental waste is another concern. The traditional scouring process is performed with sodium hydroxide, often used in lye to clean drains. It is extremely corrosive in a concentrated form because of its high alkaline content. "By itself, sodium hydroxide is not a problem, but combined with other chemicals that are used in textile finishing and dyeing, it will increase the overall inorganic chemical load in a plant's wastewater," Hardin said.

The new process leaves behind organic enzymes, which are proteins. "They're made up of the same building blocks - essential amino acids - that your mother said you had to eat when you were growing up," Hardin said. "These enzymes are much more environmentally benign because they are natural, and they easily degrade by natural processes."

But all textile waste - even enzymes - must be processed at a biological treatment plant. Laws require that industries break down organic molecules before they are released into streams.

"There'll always be some type of treatment because of what environmental regulations require," Hardin said. "But the current water treatment will handle the waste from the enzyme process as well. It'll probably cut down on the environmental load overall, and you certainly won't be creating any more problems."

Hardin's research is the first to suggest that enzymes could be used for scouring; however, enzymes already have earned a healthy respect in some other aspects of the textile industry. For example, one enzyme, a common protein called amylase, has been used by the industry for 35 years to "desize," or break down, the starch that is put on fabric prior to the weaving process.

On a loom, the yarns go back and forth through the shuttle as many as 700 times a minute, generating a tremendous amount of stress on the fabric. To lessen the amount of breakage and abrasion during the weaving process and to lower the number of times the loom stops due to broken thread, starch is used to strengthen the yarns. After the fabric is woven, the starch must be stripped away before any further processing is done.

Another enzyme, called cellulase, has been commonly used in the past five years for "biostoning." Many manufacturers substituted enzymes for the stones that were used to stone-wash fabric, such as denim jeans that look like they've been worn. Historically, this process was done by tumbling blue jeans along with numerous pumice stones in a big laundry machine.

"Sometimes you actually had pieces of stones or grit in your pocket when you bought new jeans," Hardin said. "Now most of the industry uses cellulase."

Cellulase breaks down cellulose - the molecule that makes up the cotton fiber. "It just eats away the surface of the fabric just like the stone would, but with less damage to equipment. It also prevents leftover grit in the jeans and the wastewater," Hardin said. "You can control your processes better with enzymes than you could with stones."

Hardin's project is just one of nearly a dozen research areas that involve the department faculty, many of whom also are involved in a state-wide consortium to help the textile industry remain competitive in Georgia. The energy savings coupled with the "environmentally friendly" waste in Hardin's new scouring process make this desirable, cutting-edge technology, which is why he has filed for patent protection.

Hardin has defined the essential ingredients - cellulase and pectinase - and has established which parameters must be analyzed to optimize the process for each industrial application. However, he continues to work on developing ideal conditions for the specific materials. "I'm hoping that we'll get this perfected within a year," he said.

Hardin also has the challenge of persuading industries to make the switch to the enzymatic process.

"It will be a very fundamental change in the way [textile mills] do things. We're asking them to change something that they've been doing for hundreds of years," Hardin said. "But the industry will be able to switch without investing in new machinery. If you were talking about them changing equipment, that would definitely complicate the economics."

A New York textile company, Ajoy, already has expressed an interest in Hardin's new scouring technique. The company markets a "natural" fabric, usually adorned with black specks in a beige-colored material. These specks are called motes, which are seed fragments that normally require further processing before scouring.

Hardin also has piqued the interest of the leading international enzyme companies, the Denmark-based Novo Nordisk and the San Francisco-based Genencor. These companies would mass produce the enzymes to sell to chemical suppliers, which in turn would sell to textile plants.

Hardin's work is a breakthrough approach to improving the way fabric is made. While that may not alter the nature of cotton, it could dramatically impact textile manufacturing and make a major contribution to the $75 billion U.S. textile industry.

For more information, access http://www.fcs.uga.edu/tmi/.

Catherine Gianaro is UGA's assistant director of research communications and assistant editor of Research Reporter. She has a bachelor's degree from the University of Florida College of Journalism and Mass Communication.


Return to Winter 1997 Index

Research Communications, Office of the VP for Research, UGA
For comments or for information please e-mail the editor: rcomm@uga.edu
To contact the webmaster please email: ovprweb@uga.edu