Item Required Properties Applications Brand Names
Thermosetting sealant • Hardens when heated Sealant and adhesive Drying sealant
• Non-running
Body sealant • Highly solid, no volume shrinkage Sealing of sheetmetal seams Body sealant
• Non-running (drip rails, floor, body side 3M PartNo. 8531
panels, trunk, etc.) 3M PartNo. 8646
Spot sealer • Electro-conductive, and spotwelding Spotwelding locations Spot sealer
can be done after application
• Excellent water resistance
Structural adhesive • Two-agent mixture adhesive Gluing places that cannot be Two-agent denatured epoxy
• Low Viscosity spot-welded, such as roofs adhesive (MZ 100320)
Interior trim adhesive • Highly solid, non-running Sealing for gromments, packing 3M 8513 Grommeted
• Good heat resistance and metals Windshields Sealer (Black)
• No rubber swelling
• Non-drying
Quick-drying, • Quick drying (10 seconds Excellent adhesive performance with (For Europe) 3M PartNo. 8121
high-strength adhesive to 3 minutes) most materials (except polyethylene, (Except for Europe)
• Colourless and transparent polypropylene, fluorocarbon resins 3M PartNo. 8155
after drying and other substances with
highly absorbent surface)
Wax injection Wax injection Tectyl 506
Tectyl 506T
Tectyl ML
Dinitrol 3122
Dinitrol 3654-1
Mercasol 831-ML
Waxoyl
Terotex
HV200PLUS
HV300
Rocker panel primer Rocker panel primer Glasurit FX89–7330
(Polyester basis)
Glasurit FX90–7103
(Water basis)
Underbody anticorrosion Underbody anticorrosion agent Tectyl 506T
agent Tectyl 506
Tectyl S
Mercasol NON-DRIP
Waxoyl
Dinitrol 4954
Terotex WAX
Undercoating • Non-running, good adhesion Undercoating agent 3M PartNo. 8864
• Thick application possible 3M PartNo. 8877 (For Europe)
• Good low temperature
performance
144Repair of Vehicle Bodies
synthetic-resin-based compositions. The choice of
each of the types will be dependent on the site for
application, on the eventual conditions of exposure
and often on price. These categories can be subdivided
further into the various physical forms in which
they can be made available, which include mastic
putties for hand application, extruded sections for
placing in precise locations, gun grade compositions
which have the advantage of speed and economy
of application, and pouring and spraying grades.
The properties of sealers will obviously vary
according to their type and to their application.
Thus preformed strip or putty sealers must adhere
to the surfaces to which they are applied, and must
not harden or crumble in service. Glazing sealers
must be capable of being readily applied from a
gun, with the ability to harden off on the surface,
but must remain mastic in the assembly so that they
are capable of maintaining a leak-tight joint whatever
deflection the body undergoes. Heat gelling
sealers must be capable of being readily applied by
extrusion or possibly by spraying, and then must set
up when cured but still retain a degree of flexibility.
As a result of soaring energy costs together with
the need for car aerodynamic design, direct glazing
of windscreens and fixed body glass was introduced
and an adhesive was required to bond glass windscreens
to the metal aperture. The material used is
polyurethane adhesive, sealant. It possesses a combination
of adhesion, sealant and gap filling qualities;
it is a one-component adhesive and sealing
compound of permanent elasticity. This dual-purpose
material is based on a special moisture cured
polyurethane with an accelerated setting time. The
curing time is dependent upon the humidity levels
prevailing, as well as the temperature. For example,
at 20 °C with a relative humidity level of 65 per
cent, a 6 mm diameter bead will be tack free within
1 hour and fully cured in 24 hours.
Table 4.11 indicates the uses of various sealant
materials.
4.10 Sound deadening, thermal insulating
and undersealing materials
The type of material used for sound damping or
deadening depends on whether or not it is also
required to provide undersealing. A material
required for sound deadening only will normally be
applied to the interior of a vehicle, whereas one
required to provide sound deadening and undersealing
properties will be applied to the underside of
Table 4.10Types of sealed joints used in vehicle bodywork (Rover Group Ltd )
Application Material description Application equipment
Bolted joints Between panels Performed strip Hand or palette/putty knife
Zinc-rich primer Brush or spray
Panel edges Seam sealer light Applicator gun (hand)
Spot-welded joints Between panels Zinc-rich primer Brush or spray
Structural adhesive or seam sealer
Panel edges Seam sealer light Applicator gun (hand)
Bonded joints Between panels Metal-to-metal adhesive semi-structural Caulking gun
Metals and non-metals used in vehicle bodies 145
the vehicle. Thus the former need not be fully water
resistant, whereas the latter must be water resistant
in addition to many other necessary requirements.
The sound deadening properties of a material are
related to its ability to damp out panel vibrations,
and this in turn is related to some extent (but not
solely) to its weight per unit volume. Thus the
cheapest sound deadening materials are based on
mixtures of sand and bitumen, although these tend
to be brittle. A better material is bitumen filled
with asbestos; although this is probably less effective
as a panel damper than sand-filled bitumen, it
is nevertheless more suitable owing to its better
ductility. In general, those sound deadeners applied
to the interior of the vehicle are water-based bitumen
emulsions with fillers, whereas sound deadener/
sealers applied externally should be solvent-based
materials. A more effective sound deadener than
Table 4.11Sealers used in vehicle body repair work
Type Base material Application
Visible seams Polyurethane Extremely adherent sealant used on front and rear
aprons, rear panel, engine compartment, bottom of
boot, passenger compartment, side panels, wheel
arches, vehicle underbody, tank filler caps and wings.
Can be painted over with primer and fillers after
curing, is non-shrinking, can be brushed and smoothed
with a spatula. Cures by means of air moisture
Synthetic rubber Particularly suitable for all automotive problem areas
where cleaning is difficult. Extremely adherent to raw,
degreased, bonded, primed and painted sheet steel.
Can be painted over with lacquers after thoroughly
drying. Following application, can be passed through
drying ovens at a maximum temperature of 90 °C
Acrylic dispersion (water based) Particularly suitable for sealing joints, welded seams
and butt joints on vehicle bodies. Substrate must be
primed and can be readily painted over. When cured,
is resistant to water
Structural seams MS polymer Applied by means of an air pressure pistol. All
structural seams sprayed by the manufacturer can be
re-created with this sealant, so that the original finish
can be restored after repair. Also can be painted over
immediately wet-on-wet
Nitrile-butadiene rubber Special brushable sealant used for front and rear
aprons, bottom of boot, inside floor, side walls, wheel
arches. Has excellent adhesion to raw, primed and
painted sheet metal, and can be painted over after
drying
Underbody seams Bitumen rubber Specially used for the underbody area of the vehicle.
Resistant to water, salt spray, alcohol and dilute
sulphuric acid
Overlapping joints Synthetic rubber Used for sealing bolted wings, headlight units, rear
light housings and cable inlet holes
Sealing tape Synthetic rubber Suitable for all overlapping and screwable joints on
vehicle bodies, metal to metal, metal to wood, metal
to plastic, wood to wood or plastic to plastic
Rubber profiled windows Synthetic resin, synthetic rubber Particularly suitable for sealing rubber profiled front,
rear and side window units between rubber and
glass or rubber and the vehicle body
146Repair of Vehicle Bodies
asbestos-filled bitumen is a clay-filled water dispersed
polyvinyl acetate (PVA) resin emulsion; this
has damping characteristics approximately three
times better than the bitumen-based material, but
naturally it is more expensive.
Other sound absorbing materials are now used for
insulation in the automotive industry. Needle felts
are blends of natural and manmade fibres locked
together by needle punching. These are used in diecut
flat sheet forms for attachment to moulded carpets,
floor boot mats and as anti-rattle pads. Bonded,
fully cured felts are similar blends of fibres bonded
together with synthetic resins. All the binder is cured
during the felt making process. As with needled
materials, these are mainly used for flat products,
especially where low density is required such as in
sound absorption pads and floor mats. In moulded
felts and moulded glass wool the binder is only partially
cured during the felt making process. The curing
sequence is completed under the action of
temperature and pressure in matched die compression
moulded tools to produce components which
have three-dimensional form and a controllable
degree of rigidity. Fully cured and needled products
can be given various surface treatments including
abrasion-resistant and waterproof coatings such as
latex, PVC or rubber, or they can be combined with
bitumen to improve the sound insulation properties.
Moulded felt can be supplied covered with a range of
woven textile covers or with various grades of PVC
and heavy-layer bitumen EVA products.
Polyurethane flexible moulded foam can be
modified or filled to meet different insulating
requirements in the vehicle. The foam can also be
moulded directly on to the hard layer, allowing
simple tailoring of insulation thickness.
Table 4.12 indicates the use of various undersealing
materials.
4.11 Interior furnishings