 Direct
glazing - the installation of window glass by means of adhesives
- is one of the most common applications of elastic bonding
technology, and the technique has been widely used in the car
and bus industry for a number of decades. In modern assembly
plants, the application of the adhesive - and sometimes the
actual installation of the glass - is now fully automated. Direct-glazed
windows play a large part in improving the aerodynamics (Cd
factor) of a vehicle and thereby reducing fuel consumption.
Adhesive-bonded windows also generate less noise at high speeds
and the adhesive used weighs less than a preformed rubber gasket.
In the construction of buses for example, weight savings of
up to 1.2 kg per linear metre of window surround can be achieved.
The thickness of the adhesive layer
must be sufficient to accommodate dimensional tolerances in
components as well as any thermal movement. Attention must
also be paid to the adverse effects that may result from climatic
exposure. In all cases it is important to avoid standing water
at the adhesive joint or seal. The sealed joint must also
be profiled to assist in rapid water run-off and hence avoid
water pooling. Voids should always be avoided due to the possibility
of corrosion of the substrate which then leads to a reduction
in adhesive strength or failure. Hence always design the joints
effectively.
In exterior direct glazing applications,
the interface between glass and adhesive must be shielded
against UV radiation. The usual method is to apply an opaque
ceramic screen-printed border to the glass, with a transmittance
value of not more than 0.1% for light of wavelengths between
400 and 500mm.
Black primer is not sufficient to give
UV radiation protection.
Click here to view information on
- Bond Line Dimensioning
- Corrosion Prevention.
- Handy Trade Tips
- Joint Design for Direct Glazing
Applications.
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