A recent American Chemical Society's Weekly PressPac briefly describes how Australian researchers have used nanotechnology to develop 'self-cleaning' wool and silk fabrics (scroll to article #4 in the PressPac). The researchers 'prepared wool fabrics with and without a nanoparticle coating composed of anatase titanium dioxide, a substance that is known to destroy stains, dirt, and harmful microorganisms upon exposure to sunlight.' In one of their experiments, they poured red wine upon pristine and nanotechnology-coated wool. After 20 hours, their coated fabric 'showed almost no signs of the red stain, whereas the untreated fabric remained deeply stained.' The researchers think these fabrics could become available in a near future. But read more...
You can see above FESEM (Field Emission Scanning Electron Microscopy) images of (a) pristine wool fiber, (b) modified wool fiber, (c) T60-coated wool fiber, (d) T60-coated modified wool fiber. (Credit: Monash University and American Chemical Society) Here is a link to a larger version.
And these other images above describe what happened in a recent laboratory study: "wool treated with a new nanoparticle coating (bottom row) removed red wine stains more effectively than plain wool (top row) and wool coated with another stain-fighting chemical (middle row), scientists say. (Credit: Monash University and American Chemical Society) It shows "the degradation of red wine stains on pristine PO, T60-coated TO, and T60-coated modified TS samples after 0, 8, and 20 h of light irradiation by a solar light simulator." Here is a link to a larger version of this picture.
This new kind of coating has been developed by Dr Walid Daoud, Lecturer in Organic Chemistry at the Faculty of Science of Monash University and his colleagues.
In Self-cleaning wool and silk developed using nanotechnology, Roger Highfield, Science Editor for The Telegraph in UK, gives additional comments about these new fabrics. "The coating, which is non-toxic, can be permanently bonded to the fibre and does not alter its texture and feel, they note, so a silk tie would still feel silky. The tricky part of the research was finding a way to bind the keratin to the titanium dioxide, says Daoud. 'Applying a ceramic inorganic material to organic fibres, in particular keratin protein fibres such as wool, silk, hemp, and spider silk, remained a challenge.'"
Highfield also asked Daoud when these self-cleaning fabrics would become available -- especially for self-cleaning socks. Here is Daoud's answer: "It is anticipated that as soon as the technology receives the approval technically and economically, you will then be able to see the product in the market. Currently, industrial testing and mill trials of this patent-pending technology are being conducted."
For more information, this research has been published online by Chemistry of Materials, an American Chemical Society publications under the title "Self-Cleaning Keratins" on January 23, 2008. Here is a link from which you'll be able to access the full paper in HTML version or as a PDF document (3 pages, 650 KB).
Here is the first paragraph of the introduction. "Keratins, a class of biologically fibrous proteins, are tough and insoluble due to the formation of adjacent peptide bond that allow close alignment of the sulfur-containing amino acid constituent, cysteine, enabling the formation of disulfide bridges, cross-links, that confer rigidity and thermal stability to keratinous materials, which make them an important class of fibrous materials. Keratins are a type of natural protein and the main structural constituents of animal tissues. Keratinous protein fibers such as wool, silk, hemp, and spider silk find numerous applications such as insulation, tires, and strong fibers in addition to textiles."
But even these protein fibers offer excellent physical and processing properties, they also have limitations. Here is how the researchers have overriden some of them. "In this contribution, self-cleaning keratin fibers have been realized following a bottom-up nanotechnology approach in which anatase nanocrystals of titanium dioxide are formulated and carefully applied to the fibers via a near room temperature sol–gel process in order to maintain their intrinsic properties while conferring self-cleaning properties and self-protection against UV degradation. This may enable wider utilization of these natural fibers."
Sources: American Chemical Society, February 6, 2008; Roger Highfield, The Telegraph, UK, February 11, 2008; and various websites
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