Adhesives are increasingly used in modern automotive production. They allow
different materials to be permanently bonded in an energy-efficient manner and
without the need for other auxiliary parts.
The specialty chemicals company Degussa AG
(Dusseldorf, Germany) supplies materials that are used in innovative bonding
technology to design the vehicle of the future to be even safer and more economical.
In modern vehicle construction practically all components can be bonded using
industrial structural adhesives. The benefits of structural adhesives are particularly
evident when different materials need to be bonded to each other. This is even
more important when dealing with a mix of lightweight construction materials,
where bonding would not be possible without adhesives. Cost-savings (e.g. replacement
of mechanical fasteners with adhesives) provide an additional advantage. A medium-class
vehicle requires welding at approximately 5,000 points, each costing around
five cents. More than half of these can be replaced by adhesive joins, saving
around 70 euros per vehicle. In addition, using one kilogram of adhesive reduces
the vehicle weight by 25 kilograms and adhesive-bonded vehicle bodies are more
rigid, allowing thinner sheet metal to be used.
Car body rigidity substantially improved
Direct glazing using moisture-curing polyurethane systems provides a good
example of glass-metal bonding, which is commonly used. This multifunctional
bonding holds the glass windshield in place even if the vehicle is involved
in an accident, improves the rigidity of the automotive body and allows for
Degussa has successfully marketed AEROSIL® fumed silica and PRINTEX® brand
pigment blacks for windshield adhesives for many years. They enable the production
of easy to process, strong and UV-stable adhesive products. Those are then applied
with pinpoint accuracy to the body components using automated glue guns.
The copolyester DYNACOLL® increases rapid curing and cuts assembly time.
A further development that is progressing well is the use of structural adhesives
for bonding metal. These solutions again yield significant improvements in terms
of body rigidity and crash behavior. They also offer the advantage of reduced
weight, versatile design options and structural rigidity. All these advantages
should significantly increase the market prospects for these plastic/metal combinations
in the future.
Good wet and dry adhesion
At present, single-component epoxy resins or two-component polyurethanes are
used for structural adhesives. This demands that the adhesives provide a great
deal of functionality even under adverse outdoor conditions, something that
can only be achieved by adding suitable chemical additives. For example, when
used in structural adhesives silanes such as DYNASYLAN® increase wet and dry
adhesion (“adhesion promotion”). At the same time they improve resistance to
solvents, heat, humidity and weathering. They also optimize the mixing behavior
of the adhesive components and make processing very much easier.
Hot melt adhesives for interior ecology
Similarly, adhesive technology offers advantages in the passenger cab, where
diverse materials such as textiles, leather and plastics are bonded to one another.
Apart from commercial viability, ecological aspects in particular play a significant
role when selecting an adhesive for this area of the vehicle.
Customized hot melt adhesives based on DYNAPOL® S and DYNACOLL® satisfy these
sophisticated requirements: They achieve a maximum adhesive strength very rapidly,
enabling the next stage of processing the adhesive-bonded components to take
place immediately. Solvent-free adhesive reduces unpleasant evaporation in new
cars, an occurrence known as fogging.
Debond “at the press of a button”
One of the biggest challenges in the chemical industry is to manufacture an
adhesive bonding that can be undone. This is because whereas car bodies made
from welded steel can be easily melted down, vehicles manufactured from a mix
of adhesive-bonded materials remain a problem today from the recycling point
of view. What is needed is an adhesive that will lose its adhesive properties
on command, as it were.
This is precisely what the adhesive additive MagSilica®, produced by the internal
start-up company Degussa Advanced Nanomaterials, accomplishes. Adhesives containing
MagSilica® can be heated using an alternating magnetic field, and as a result
they cure much faster than conventional products. Bonds created using this process
can be undone using very selective heating, which results in the adhesive bond
“switching off” again.