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Feature Fastening & joining
Stick to the right adhesive
As there is no universal adhesive, making
minutes, although some can subse-
quently be heat cured by, for example,
the right choice is vital for successful
passage through a paint bake oven.
bonding. Colin Chapman of Henkel, maker
These adhesives can be applied by
means of an automatic mixing gun or,
of Loctite brand adhesive products,
alternatively, by having the catalyst
applied to one surface, the adhesive to
discusses the options
the other and the two parts mated.
Their bond strength means they are
used for automotive, marine and gen-
D
ifferent adhesives are designed
RIGHT: Among the
eral industrial applications that entail
for specific types of applica-
range of anaerobics
the bonding of magnets and ceramics,
tions - and if the wrong product
is a selection of
or joining metal to plastic or ceramics.
is used, chances are the bond
retaining com-
will not give ultimate performance.
pounds used to
Anaerobics
The best bet is to gain an understand-
bond cylindrical
Anaerobics are single component
ing of each adhesive technology and
components
materials which remain liquid in the
select the most appropriate for the job. presence of air and only cure when the speaking, the residual m oisture found
joint has been assembled. These adhe- on most substrate surfaces is adequate
Epoxies sives are used on metallic components to prompt curing, although in some
Where there’s a call for high strength for locking and sealing threads, for instances, an activator will aid this pro-
structural bonding, epoxy resins are providing gaskets and for bonding cedure. However, this dependence on
generally the first choice. That’s why components such as retaining gears, surface moisture means CAs have a
they are used for a diversity of applica- pulleys and bearings on shafts. limited cure-through depth of about
tions in industries such as automotive, Most adhesives work best on clean 0.25mm.
aerospace, marine, oil drilling, civil surfaces and this is still ideal. Where the relative humidity is 30
engineering, leisure goods, medical However, developments have seen per cent or less or with substrates that
devices and electronic assembling. formulations which allow as-received generate naturally low moisture levels,
Alongside strength, epoxies provide parts to be successfully bonded. the cure times could be extended. To
resistance to chemicals, corrosion,
An epoxy is used in
compensate, the application of solvent-
fatigue and thermal shock. They also
conjunction with
Light-curing acrylics based activators will speed up the cure
possess the capability of joining
rivets to provide
These adhesives are single-part, and the ability to cure through volume
dissimilar materials and can be used
total security for
solvent-free adhesives available in var- is also possible.
in high temperature environments.
this ice axe used by
ious viscosities. Among the benefits
By selecting the most appropriate
mountaineers
are the ability to produce clear bond Light-curing cyanoacrylate
epoxy and suitable design parameters, lines, physical toughness, speedy Around a decade ago, light-curing
they will resist severe stresses without cure-on-demand and exceptional cyanoacrylates were introduced which
loss of structural integrity. adhesion to a variety of substrates, enable the benefits of both cyanoacry-
including heavily plasticised PVC. lates and light-curing acrylics to be
Toughened acrylics Light-curing adhesives incorporate exploited. These adhesives surface
These are two component adhesive
A Cyanoacrylate
photo-initiators which turn light cure immediately when exposed to
systems which are suitable for bond- adhesive will energy into the chemical energy low-intensity UV or visible light, cure
ing metals, some plastics and woods. provide an instant needed to initiate the curing process. in shadowed areas, and adjust easily to
They develop handling strength at bond with excellent Previously, such adhesives required automated production lines. They
room temperature within 15 to 30 strength ultra violet light sources to start this require no second-step accelerators or
cure, but new formulations mean visi- activators and cure to depths bigger
ble light sources can be employed. than 6mm within 15 seconds.
The ability of light-curing adhesives
to cure on demand is a major incentive Polyurethanes (PUs)
in using them. Once the adhesive is Supplied as either single or dual part
applied, sufficient time can be taken to products PUs are offered in a wide
position parts correctly because curing multiplicity of cure speeds, viscosi-
will not begin until the joint is sub- ties, strengths and chemical resistance
jected to the appropriate light source. capabilities. Renowned for their out-
standing flexibility, PUs also provide
Cyanoacrylate adhesives (CAs) very good gap filling properties and
These are one-part products, also the ability to produce dependable
known as super glues or instant adhe- seals. For these reasons polyurethanes
sives, that cure at room temperature. are used to bond windscreens and
Because of their rapid cure time, fixture windows into vehicle bodies.
in just a few seconds, with complete
bond strength in 24 hours - CAs are Henkel Loctite
ideal in situations where automated T: 01442 278100
production is involved. Generally www.loctite.co.uk Enter 311
Factory Equipment JANUARY 2010 19
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