May 3, 2011

Understanding the Dynamics of Fabrics

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The touch, the feel of cotton is in the cotton fibers themselves. How fabrics feel to us, known as “tactile performance” in fiber science, depends on their physical properties. Prof. S. Kay Obendorf, fiber sciences and apparel design, studies the chemical and structural properties of textiles. “Fabric structure, yarn structure, fiber structure, fiber size, cross-sectional shape, length of the fibers – all matter. Everything in textiles affects the tactile performance,” explained Obendorf. The size of fibers is major factor determining how a textile feels. Synthetic fibers like nylon and polyester once felt stiffer than cotton because the fibers were larger than that of the naturally made microfiber, cotton. Today, though, synthetic microfibers are made smaller, and, as a result, softer. The next frontier of soft textiles: nanofibers. “You can’t even see that they’re fibrous. They’re ultrasoft,” said Obendorf of nanofibers. With diameters less than one micrometer, these tiny fibers can be made by electrospinning, a process that uses electric charge to draw droplets out of liquid that become individual fibers. Obendorf’s group creates metal oxide-coated textiles that trap toxic chemicals and break them down into smaller, less toxic chemicals. The group members use nanofibers as the base of their clothing, creating their own fibers through electrospinning. Changes to the textiles can change the fabrics’ feel. Obendorf explained, “Addition of functional properties often change the tactile properties of textiles.  For example the addition of metal oxides increases the stiffness.” The group is developing the textiles to be used as protective clothing or even in built environments, to improve air quality. Another way to get softer fabrics is by coating them with chemicals. Fabric softeners act as chemical lubricants of textiles. The oily chemicals in fabric softeners become distributed over the fibers of clothing in the laundry. Once the clothes are clean, the remaining fabric softener reduces the friction between your hand and the fibers. By reducing the resistance to the friction caused from rubbing our hands on the fibers, we perceive the coated fibers as softer. The mechanism of fabric softeners also explains why some fabrics don’t benefit from their use, like towels. They lose their ability to absorb moisture when treated with fabric softener, which make them more water repellant. In 2009, Obendorf published a scientific article that investigated the distribution of fabric softeners over cotton fibers and also explored the relationship of fabric softener distribution to perceived softness. “It appears that you do not need a large amount of fabric softener on the surface to make it softer,” she described, based on her results. Once a certain amount covered the surface, more fabric softener didn’t lead to a softer feel. Besides making fabrics soft to our sense of touch, fabric softeners also please our sense of smell. “The biggest thing fabric softener does is distribute fragrance; thus fabric softeners influence both tactile and aroma sensual responses” said Obendorf.

Original Author: Daina Ringus