Oxygen inhibition can be prevented by using short and medium
wavelength UV because the higher energy causes a quicker
breakdown of the photo-initiators, meaning there is less time
for oxygen to penetrate the exposed adhesive surface.
balance of curing light
(approximately 300-450 nm).
In some cases, the use of a
bulb with higher amounts of
short-wave UV (a mercury
UV bulb) will overcome
oxygen inhibition.
If a manufacturer is using
an LED UV curing lamp, one
thing to consider is their
ability to cure tack free. As
discussed, oxygen inhibition
can be prevented by short
and medium wavelength UV
curing light. LED UV curing
lamps emit narrow spectrum
light, primarily in the long
wave zone, and so may
struggle to achieve a tack free
cure with some adhesives
that are prone to oxygen
inhibition.
EXCLUDE OXYGEN FROM
THE SURFACE
A third option is to exclude
oxygen from the adhesive
surface, such as to place a
thin film of plastic over the
adhesive and cure through
the plastic. Many adhesives
will have poor adhesion to
plastics like polypropylene or
polyethylene and so they can
be removed easily post cure.
Another way to do this is to
cure under an inert gas like
nitrogen or argon.
If tackiness cannot
be avoided by making
improvements to the process,
the manufacturer may
want to consider removing
the tacky layer with an
isopropyl alcohol (IPA)
wipe. Alternatively, the
manufacturer can change
adhesives, opting for one
less sensitive to oxygen
inhibition.
Perhaps the most optimal
scenario would be to specify
an adhesive formulated to
cure tack free with LED
UV curing lamps, so that
the considerable benefits
of modern LED UV curing
technology can be realised.
If you are experiencing
sticky or tacky surfaces on
your adhesive or coating,
our recommendations are
to use a higher intensity
UV light, use more short
wave UV light, exclude
oxygen from the surface
or change the adhesive to
one less sensitive to oxygen
inhibition. Partnering with
an experienced adhesives
supplier will help you to
specify a suitable adhesive
and understand the
curing process including
wavelengths, intensity and
exposure time.
Intertronics
www.intertronics.co.uk
01865 842842
www.fastening-solutions.co.uk 15
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