Wednesday, December 23, 2009

Chinese Scientists Give Wool a "Brain" with Silica Nanoparticles Making it a Smart Fabric

 Super Hydrophobic Wool: These images from an electron microscope show wool fibers coated with  silica nanoparticles that may improve wool’s qualities.

Image Credit: American Chemical Society

Scientists in China are reporting an advance that may improve the natural wonders of wool — already regarded as the "wonder fabric" for its lightness, softness, warmth even when wet, and other qualities. They say the discovery could give wool a "brain," placing it among other "smart" fabrics that shake off wrinkles, shrinkage and "breathe" to release perspiration. The study is in ACS' Langmuir, a bi-weekly journal.

Fangqiong Tang, Yi Li and colleagues note that wool is naturally water-repellant, or hydrophobic, a feature that acts as a barrier to enhanced features such as anti-wrinkle, anti-shrinkage finishing and dyeing. Wool's water-repellency also hinders its ability to absorb moisture and makes wool garments feel sweaty. Although scientists have developed treatments that make wool more hydrophilic, or water-absorbing, they may not last long, may damage the fabric, and are not environmentally-friendly.

The scientists describe development of new coating that appears to ease these problems. It is made from silica nanoparticles of 1/50,000th the width of a human hair. The particles absorb excess moisture, and make wool superhydrophilic. The new layer does not affect wool's color or texture and can withstand dry cleaning, the scientists note.

The method for fabricating environmentally stable superhydrophilic wool fabrics is simple. An ultrathin silica layer coated on the wool altered both the surface roughness and the surface energy of the fiber and endowed the wool fabrics with excellent water absorption. The process of coating silica sols was dependent on an acid solution of low pH, which influenced the electrostatic interactions between nanoparticles and wool fibers. The morphology and composition of silica-sol-coated wool fabrics were characterized by a combination of SEM, TEM, EDX, FTIR, and XPS measurements.

The possible mechanism and size effect of silica nanoparticles on the hydrophilic property of wool fabric were discussed. The washing fastness of the superhydrophilic wool fabrics in perchlorethylene and water was also evaluated. This study shows that wool fabrics modified by optical transparence, chemical stability, and nontoxic silica sols are promising in constructing smart textiles

"Fabricating Superhydrophilic Wool Fabrics"
Fangqiong Tang, Ph.D.
Technical Institute of Physics and Chemistry
Chinese Academy of Sciences
Beijing, People's Republic of China
Phone: 86-10-825-43521
Fax: 86-10-62554670

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