Tensile Shear
Cleavage
Peel
Adhesives & Sealants
Surface treatment and first operations :
A good bonding is the result of proper surface preparation.
The adhesion is good when the surface is clean and:
All impurities coming from the mechanical working, treatments, oxidations,
residuals of release agents, have been removed.
The surface to bond has been activated with primers or by treatments like
flame, corona, or plasma, in order to improve the polarity and the presence
of reactive groups.
Before bonding it is recommended to check the materials and to verify with
a practical test or from laboratory literature the resistance of the substrate.
Especially for plastic bonding, where the category is very wide as it includes
a high number of different compositions, it is important to select with
attention the proper treatment or chemical base of the primer.
Cleaning and degreasing with solvents:
To remove oils and greases we recommend the use of solvents which
do not leave residuals after drying. In the case of plastic substrates,
it is important to verify the resistance of the material to the solvent.
Alcohol based solvents work well with no, or limited, aggression on the supports.
To remove lubricants we recommended a solvent based on, or containing,
exane. Acetone, or ketons are considered quite aggressive on plastics
and are mainly recommended for metals or rigid materials with high
chemical resistance.
Mechanical treatment
(roughening, sand blasting, brushing):
Mechanical treatment is one of the used methods to remove oxidations on metals.
The surface roughening improves the adhesion thanks to the fact that
the overlapping area is increased. It is important not to exceed with
the size of the grain, as it might result in a poor capability of the adhesive
to wet properly the surface to bond.
Recommended grain size is from 300 to 600 for Alluminium and about
100 on Steel. Roughening is possible on composite materials with some
attention, due to the fact the fibers of the substrate might be damaged
with the result of a more fragile composite.
After any mechanical treatment, it is very important to remove all residuals
and to clean/degrease with solvents.
Chemical treatment
Recommended on very inert and resistant materials, or when it is not possible
to work on the substrate. Forming reactive groups, which are not originally
present on the surface, allows the adhesive to make a chemical bond.
Treatment with primer
Primes are applied using specific substances in a solvent solution, to make a
bonding layer between the reactive groups of the adhesive and the substrate.
Before the application of the adhesive, it is very important to allow the primer
to completely dry. This is because primers contain solvents which have to fully dry.
Plasma treatment
This method is particularly effective on low surface energy substrates
(e.g. Poliolephins and Plastics). The cleaning and activation of the surface
takes place rapidly and with reliability, with no need of solvents or other
dangerous products. Easy engineering of the treatment and required
equipment, possible in different environments (vacuum, room pressure,
nitrogen atmosphere or air). The treatment remains active for a limited time.
The bonding is recommended within 24-36 hours.
How to apply the adhesive and key
aspects to keep in mind:
Elantas Europe adhesives are available in a cartridge kit, cans, tins and drums.
Some basic precautions are important. When using a cartridge kit,
it is important to remember to purge the first part of the mixed material
coming from the static mixer, selected among the various sizes in function
of the reactivity and viscosity of the adhesive.
In most cases, two part systems (resin and hardener) are supplied with
different colours. This helps in the case of manual application as it will be easier
to see when the material is properly mixed.
The adhesive must be applied homogeneously, with a thickness between 0.05
and 0.2 mm, and with the application of a uniform pressure on the bonding area.
For most applications a suitable quantity of adhesive goes from 100 g to 400 g
per square meter, with a resulting thickness of about 0,1 mm.
Some adhesives, after the application, can be sensitive to humidity or inhibited
by oxygen or carbon dioxide.
It is advisable to close the joint in short time. The curing profile of the product
is a function of its formulation, and must be adjusted to the specific testing
and working conditions of the bonded device.
Geometry of the bond and strength:
a proper design of the bond is one of the most important aspect for an optimal use of the adhesive. Our technical service will help you to define the best material to
match the geometry, stress, and substrates which the bond will be subjected.
Examples of bond geometries and stress mode.