Pilkington Activ™ - the explanation...
Unique Dual Action Technology
Despite its exceptional properties, Pilkington Activ™, the world's
first self-cleaning glass, requires no unusual treatment or care procedures
during processing, fitting or once installed. How does it work?
In March 2001, following one of the industry's most thorough and extensive
development and testing programmes, and supported by intensive market
research throughout Europe, Pilkington announced the European launch of
Pilkington Activ™, the world's first self-cleaning glass.
Although
initially targeting the home improvement sector, Pilkington Activ™
self-cleaning glass will be equally effective when installed in inaccessible
glazing applications which are difficult to access, such as atria, or
large-scale architectural glazing projects. Its use could, in many such
installations, preclude the need for complex and expensive window cleaning
equipment and specialist cleaning contractors.
The key element of Pilkington Activ™ self-cleaning glass is a microscopically
thin, transparent coating of titanium oxide. Knowledge of the properties
of this compound in relationship to glass has been widely available for
as long as 20 years. However, it is the on-line application of the coating
that has been perfected and patented by Pilkington technologists.
This coating is permanently bonded to the surface of the glass by a special
manufacturing process. The overall thickness of the coating, which has
several distinct chemical layers, is around 50nm (50 millionths of a millimetre),
giving the product a slightly clearer appearance than normal glass.
The surface coating has two important chemical properties which, when
combined, make the glass "self cleaning". First, it is hydrophilic,
that is, it attracts water and causes it to "sheet" on the surface
of the glass, preventing the formation of separate droplets and ensuring
that loose particles of dust and dirt can be washed naturally from the
surface during normal rainy weather.
Secondly,
it is photocatalytic, that is, ultra violet (UV) radiation - always abundant
in outdoor daylight - causes it to react chemically with unwanted deposits
of organic dirt, oxidising them and breaking their adherence to the surface
of the glass. After an initial "running in" period of several
days, during which the coating gradually becomes active, UV radiation
absorbed during daylight hours is sufficient to ensure that the necessary
chemical reactions continue through the night.
As this chemical activity is continuous, even heavy soiling will eventually
be broken down sufficiently to wash naturally off the glass during showers
of rain. Regular cleaning should not normally be necessary, but for unusually
heavy or tenacious soiling, or in periods of little or no rainfall, hosing
or washing down with clean water can help the cleaning process along.
The use of detergents or proprietary glass cleaning chemicals should not
normally be necessary, although their occasional use will not harm the
surface coating. The use of metal scrapers or abrasives is, however, not
recommended since this can mark the coating.
In
both laboratory and real-life window tests, the self-cleaning action of
Pilkington Activ™ coated glass was shown to be highly visible, particularly
when wet, and with no discernible deterioration over time. The chemical
coating is tough, and very resistant to naturally occurring substances
such as salt and mild acids. Pilkington claim that it should last for
the lifetime of any double-glazing unit that uses the new glass, so long
as recommended handling and cleaning instructions are followed. The coated
side of Pilkington Activ™ glass can be identified using a simple
hand-held detector, available from Pilkington.
General Handling and Care
In most respects Pilkington Activ™ glass can be treated like ordinary
glass. Subject to certain careful handling and storage recommendations,
it can be cut, toughened, machine washed and laminated. For double glazing
or decorative purposes, leading or coloured overlays can be applied to
the coated surface, just like normal glass. It will retain its anti-soiling
behaviour after all of these processes, although chemical performance
will, of course, be lost in those areas covered by any applied material.
The coated surface is hard and not easily damaged, so no particular precautions
are necessary in general handling. However, because the coated surface
is microscopically textured, the same care should be taken when handling
the glass that would reasonably be taken with any other coated glass.
Pilkington Activ™ is a trademark of Pilkington plc.For further details
on Pilkington, and Pilkington Activ™ Self Cleaning Glass please see
the website at www.activglass.com