- Self-cleaning glass
Self-cleaning glass is a specific type of
glasswith surface which keeps itself free of dirt and grime through natural processes.
The first self-cleaning glass was based on
thin film titanium dioxidecoating. The glass cleans itself in two stages. The " photocatalytic" stage of the process breaks down the organic dirt on the glass using ultravioletlight in sunlight(even on overcast days) and makes the glass hydrophilic(normally glass is hydrophobic). During the following "hydrophilic" stage rainwashes away the dirt, leaving almost no streaks, because hydrophilic glass spreads the water evenly over its surface. [http://news.bbc.co.uk/2/hi/technology/3770353.stm BBC News] , 8 June 2004] .
Titanium dioxide is a material of choice because it is characterized by high photocalytic properties, chemical stability and low price. Its
anatasephase is most photocalytic. What is more, under the UV irradiation its surface structure changes to generate OH groups, making it superhydrophilic. [ SUmio Sakka (ed.) (2005) "Handbook of Sol-GelScience and Technology Processing Characterization and Applications", [http://books.google.com/books?id=QTCyQoTVZWkC&pg=PA385&lpg=PA385&dq=%22sol-gel%22+%22self-cleaning+glass%22&source=web&ots=Rp4oyipTPD&sig=brnjh6hjbQDRs-JKuqAE7sXB3HM#PPA385,M1 Chapter 18, "Coatings with Photocatalyst on Architectural Glass"] . ISBN 1402079680.]
It is speculated that other possible application areas are computer monitors and PDA screens, where
fingerprints are undesirable. [ [http://www.engadget.com/2004/06/04/self-cleaning-glass/ "Self-cleaning glass"] , " Engadget," June 4, 2004.]
Titanium dioxide–based glass cannot decompose thick non-transparent deposits, such as paint or
silicone, waterstopfingerprints or bleeding after weathering, or stuccodust produced during construction.
Another approach to self-cleaning glass is suggested basing on the hydrophobic "
lotus effect". [ [http://www.sciencedaily.com/releases/2005/01/050125085826.htm "'Bumpy' Glass Could Lead To Self-cleaning Windows, Slick Micromachines"] , " Science Daily", January 28, 2005.]
Since 2001 the TC24 "Coatings on Glass" committee
International Commission on Glasshas been trying to set up test methods for evaluation of photocatalytic self-cleaning coatings on glass. [ [http://www.icg.group.shef.ac.uk/tc24.html#Index TC24 reports] ]
* The Pilkington Activ brand by
Pilkingtonis claimed by the company to be the first self-cleaning glass. [ [http://www.pilkingtonselfcleaningglass.co.uk/ Pilkington Glass Manufacturers] ] It uses the 15 nm thick transparent coating of microcrystalline titanium dioxide. The coating is applied by chemical vapor deposition"A comparative study of three techniques for determining photocatalytic activity", Journal of Photochemistry and Photobiology A: Chemistry, Volume 188, Issues 2–3, 2007, Pages 387–391. doi|10.1016/j.jphotochem.2006.12.040]
* The SunClean brand by
PPG Industriesalso uses the coating of titanium dioxide applied by a patented process. [ [http://corporateportal.ppg.com/NA/Glass/ResidentialGlass/Homeowners/ProductInformation/SunClean/SunCleanHowItWorks.htm SunClean glass info] ]
* Neat Glass by
Cardinal Glass Industrieshas the <10nm titanium dioxide layer applied by magnetron sputtering[http://www.cardinalcorp.com/data/tsb/cg/CG05.pdf Neat Glass] , Cardinal CG Technical Service Bulletin # CG05-06/06.]
* SGG Aquaclean (1st generation, hydrophylic only, 2002 [ [http://www.theglazine.com/newsarchive/news271101.html "Saint Gobain launches self-cleaning glass"] ] ) and Bioclean (2nd generation, both photoctive and hydrophilic, 2003 [ [http://www.saint-gobain.co.uk/main.asp?nid=37 Saint-Gobain Glass launches 2nd generation self-cleaning glass] ] ) by
Saint-Gobain. [ [http://www.selfcleaningglass.com/technical-support.asp SGG Bioclean technical info] ] The Bioclean coating is applied by chemical vapor deposition.
ETFEfilms, transparent polymerfilms described as self-cleaning
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