Getting Cotton Moisture Just Right for Processing
Cotton is the world's most widely used textile fiber, with U.S. growers
providing 20 percent of the world's output.
Maintaining proper moisture in cotton bales is critical for successful
textile processing. Too little moisture and the cotton is susceptible
to damage. Too much moisture makes cotton stick to machinery components.
So investigators in ARS' Cotton
Quality Research Unit in Clemson, South Carolina, are working to make
it easier to regulate the amount of moisture throughout processing.
The scientists, led by textile technologist David D. McAlister, used
various methods to condition samples taken from a bale of cotton. Some
were left in ambient room conditions, and others were sprayed with waterboth
with and without a wetting agent to improve water absorption. Then,
the team measured fiber properties and yarn tensile strength of each
sample to see which moisture level most improved cotton fiber processability.
They found that a spray of 4 percent water plus 2 percent wetting agenta
total of 6 percent added bale weightbest maintained fiber and
yarn strength. The research is now part of a 3-year cooperative research
and development agreement with Cotton Conditioners, Inc. (CCI), of Knoxville,
Tennessee, to see how this approach works in a real-world setting. Together,
ARS and CCI will develop, evaluate, and commercialize an effective automated
system to measure and adjust moisture content of cotton during processing
in textile mills.
At the mill, cotton bales are typically opened and allowed to condition,
or rest, for at least 24 hours. This allows them to "bloom"
as they reach moisture equilibrium with their surroundings. But in this
age of just-in-time manufacturing, it's no longer practical to do this.
Plus, moisture levels aren't monitored during this conditioning time.
In McAlister's unit, researchers monitored 250 cotton bales being prepared
for cotton mills. Bales arriving from the gin contained from 2.3 percent
to 8.2 percent moisture. Those already at 8.0 percentthe recognized
commercial idealwent straight to processing.
When bales that were low in moisture were boosted to a moisture content
of at least 6.5 percent, processing and fiber and yarn quality improved.
Bales processed with less moisture yielded inferior yarn.
In the future, many gins will have automated moisture-control technology
so bales will emerge from the gin with a prescribed amount of moisture.
ARS researchers at Clemson and at the Cotton Ginning Research Unit in
Stoneville, Mississippi, are working together to determine the optimum
moisture level for storage. If it's found to be the same as for initial
processing at the mill, then bales may need to be hydrated only onceat
the gin. In the meantime, moisture control during bale opening at the
mill may provide a rapid, practical solution to the industry's cotton
bale conditioning problem.By Jennifer Arnold,
formerly with ARS..
This work is part of Crop Quality and Utilization of Agricultural
Products, an ARS National Program (#306) described on the World Wide
Web at http://nps.ars.usda.gov.
"Getting Cotton Moisture Just Right for Processing" was published in the May 2002 issue of Agricultural Research magazine.