labelling but that would not be the case
today. Continuous development, however,
has seen their formulation change in line
with these new regulations and users can
therefore be assured they are adopting the
best practice in terms of workplace safety.
R eal life applications
B etter and better
All thread locking adhesives under the
LOCTITE® brand are anaerobic, which
means they only cure in the absence
of air. Indeed, it was the very problem
of vibration that led Dr. Vernon Krieble
– the pioneer of LOCTITE® adhesives –
to develop anaerobic adhesives. This
technology enables the adhesive, when
applied to a bolt, to stay liquid almost
indefinitely until the nut is applied.
With no air in the contact areas, the
adhesive soon solidifies to a tough
thermoset plastic.
Although this is a relatively mature
technology, advancements continue to
be made. There is now a huge range
available offering differences in viscosity,
strength, temperature resistance, chemical
resistance, oil tolerance, cure speed and
hardness/flexibility. Products are now also
rated for higher temperature use and are
more tolerant of surface contaminants.
So how is adhesive thread locking being
applied in the engineering world? An
example that demonstrates this method’s
ability to withstand an extreme, high
vibration environment is on a snow drive
jam nut within the clutch assembly of a
snowmobile. In a similarly safety-critical
application, a manufacturer of tow hitches
and couplings is using a thread locking
adhesive to secure the grub screw in the
pin that retains the trailer on the vehicles.
Again, there is no margin for failure.
Another example is an application on
the tunnel boring machines that are
excavating the extension of the Crossrail
Line through London. In common
with other giant TBMs manufactured
by Herrenknecht AG, these machines
were constructed using a thread locking
adhesive to lock bolts which have to resist
massive pressure as the machines eat into
the sub-soil. Elsewhere, another user is
applying adhesive to threads of plastic
air diffuser mushrooms for securing to
stainless steel pipe manifolds in sewage
treatment plants. The joint needs to offer
sufficient strength to last for the lifetime of
the system. Rework or repair, for obvious
reasons, are not particularly desirable.
Continuous development of product
chemistry is especially important in
the light of changes relating to CLP
Regulations. This is a European Regulation
on classifications, labelling and packaging
of chemicals that has been implemented
in stages since 2009. In summary, thread locking adhesives
not only resist vibration but also protect
against shock and thermal cycling, seal
against corrosion and prevent galling. In
addition, the joints provide better clamp
retention than mechanical clamping
devices and offer straightforward
disassembly using correctly specified tools.
The LOCTITE® Health and Safety range is
a good case in point in this regard. When
these products were introduced, their
chemical components required no hazard For more information on this subject visit
www.loctite.co.uk
Issue 27 PECM
81