Product Selection Guide
Matching 3M Structural Adhesives to your design,
performance and process requirements
January 2019
Design with Confidence.
Build to Last.
In today’s world, successful new products demand advancements in design,
manufacturing processes and end-use performance. Industrial engineering and
design professionals around the world depend on 3M
™
Scotch-Weld
™
Structural
Adhesives to help them design beyond the limits of mechanical fasteners to create
next generation products.
Trusted innovations from
aerospace to office space
With over 60 years of experience developing innovative structural adhesives for
aerospace, automotive and hundreds of other industries, 3M delivers the solutions you
can trust. Our advanced formulations create durable bonds, even on challenging
materials or in extreme conditions.
3M global service and support
3M supports our customers with the testing, technology, and training needed to
create better products. Our world-wide support staff has the xperience you can
rely on for everything from structural adhesive selection to process improvement.
Leverage 3M’s proven selection of structural adhesives, deep industry expertise,
and technical support to your advantage. Design with Con idence. Build to Last.
3M
™
Scotch-Weld
™
Structural Adhesives are
transforming the way engineers think.
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Advancing design, process and performance
The benefits f designing and building products with 3M
™
Scotch-Weld
™
Structural Adhesives help drive product
success. Eliminating mechanical fasteners provides a wide range of benefits for all stages of product development.
Design Solutions
Improve Aesthetics:
Improve product appearance with
invisible joints and smoother bond lines, reduce weight
and noise, enhance corrosion and fatigue resistance,
and more.
Freedom of Design:
Join composites to metal, build
with hard-to-bond plastics, and use thinner, lighter
weight materials.
Process Efficiencies
Enhance Productivity:
Reduce labor and material costs,
build faster with minimal surface prep and match cure
rates to your process needs.
Accurate and Easy:
Dispense by hand or with automated
equipment, and choose from a wide range of viscosities
and fl w rates.
Performance Optimization
Strong, Flexible Bonds:
Adhesives bond and seal
simultaneously, eliminate stress concentration and absorb
shock and vibration for durable bonds.
Increased Durability:
Resist chemicals, environment,
galvanic corrosion, fatigue, and material separation along
edges or corners.
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Simplifying Adhesive Decisions
for Your Application
The following questions will help you narrow adhesive choices
to a few possibilities for evaluation.
Q:
What materials
Q:
What types of
will be bonded?
by adhering to the top surface
of the bonded parts, so it’s
important to know the exact
material and condition on
those surfaces. For metals,
will the adhesive be applied
to bare metal, or will there be a paint or coating on the
surface? For plastics, exactly which base resin? Could there
be residual release agents on the surfaces used for
mold release?
A:
Structural adhesives work
joints are best for
structural adhesives?
Q:
What is the preferred
cure speed?
adhesive must have enough
work life (open time, pot life)
to allow proper mixing and
application of the adhesive
and assembling of the bonded
parts. Smaller assemblies or
shorter cycle time production processes may be able to use
a faster curing adhesive with a work life of only
five
minutes
or less, while larger assemblies that require alignment and
clamping will probably need a work life of 20 minutes or more.
A:
The chosen structural
adhesive bond under shear,
tension, or compression
forces will provide the highest
strength. Designs that tend
to apply peel or cleavage
forces to the adhesive, where the applied stresses are not
distributed over the entire bond area, will have lower bond
strength, but the bond may still be sufficient for the needs
of the application. In addition, optimum bond line thickness
typically ranges from 0.005" to 0.020". The adhesive
qualification process should always include testing of
prototype assemblies to ensure the adhesive will provide
enough performance.
A:
Joint designs that put the
Q:
How are structural
adhesives used
and applied?
Q:
What surface
preparation will
be required?
in many forms, including low
viscosity liquids and non-sag
pastes, one- and two-component
formulations, short and long
work lives, and various package
sizes and shapes. Most two-part structural adhesives
are available in both bulk containers and convenient,
easy-to-use cartridge mixing systems.
A:
Structural adhesives come
generally prefer clean, rough,
dry surfaces for highest
bond strength. This typically
means either light abrasion
and solvent cleaning of the
surface, or solvent cleaning followed by chemical etching
or applying a primer. Adhesion tests should be performed
to determine the adequate surface preparation for a
specific application.
A:
Structural adhesives
Q:
What are the general
characteristics of
the different types of
structural adhesives?
provide at least 1,000 psi
of overlap shear strength to
aluminum, but the different
adhesive chemistries have
various properties:
A:
All structural adhesives
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•
Epoxy adhesives
come in both two-part adhesives (that
cure upon mixing the two components) and one-part
adhesives (that cure with temperature). They generally
have the highest strength and overall performance. They
also provide the best resistance to high temperatures,
solvents and outdoor weathering. They adhere well to
metals, woods and concrete, and the
flexible
epoxy
adhesives also bond to some plastics and rubbers. Epoxy
adhesives usually require clean, abraded surfaces to
obtain maximum bond strength.
Tensile
•
Acrylic adhesives
are two-part adhesives that provide
excellent bond strength and durability, although slightly
lower than epoxy adhesives. However, they have
several features that make them easier to use in many
applications and manufacturing processes. These benefits
include a much faster cure speed, higher tolerance for
oily or unprepared bonding surfaces and the ability to
bond a wide variety of materials, including nearly all
plastics. Newer acrylic adhesive formulations are room
temperature stable with a long shelf life, and some have
much lower odor than regular acrylic adhesives.
Tensile
is pull exerted equally over the entire joint. Pull direction
is straight and away from the adhesive bond.
Shear
•
Urethane adhesives
are two-part adhesives that are
relatively
flexible
when cured, and therefore tend to
have excellent impact resistance and good adhesion to
most plastics. They also bond well to woods, concrete
and rubbers, but they tend to have reduced resistance
to solvents and high temperatures. Uncured adhesive
components are sensitive to moisture.
Shear
is pull directed across the adhesive, forcing the
substrates to slide over each other.
Cleavage
•
Cyanoacrylate adhesives
(instant adhesives) are one-
component, lower viscosity liquids that cure extremely
quickly with just contact pressure and surface moisture.
They adhere well, with thin bond lines, to plastics, metals
and rubbers. With the use of primers, they can also
adhere to low surface energy plastics and elastomers.
They tend to have low
flexibility,
peel strength and impact
resistance compared to other structural adhesives. They
are generally used for applications such as gasket bonding
and smaller assemblies.
•
Anaerobic adhesives
are one-part adhesives that cure
on active metal surfaces when oxygen gets excluded
from the bond line. These products keep your factory
running efficiently, reducing maintenance and leakage.
They do not bond well to glass, plastics or rubbers, and
are primarily used for applications such as locking threads
and sealing pipe connections.
Cleavage
is pull concentrated at one edge of the joint, exerting
a prying force on the bond. The other edge of the joint is
theoretically under zero stress.
Peel
•
PUR adhesives
(Polyurethane-reactive adhesives) are
one-part adhesives that apply like a hot melt, but cure
with ambient moisture for near structural strength bonds.
Fast set times and build strength over the next 24-48
hours can reach as much as 1,000 psi in overlap shear
strength. They are
flexible
and resistant to temperature
extremes and most solvents. Most commonly used in
bonds where at least one substrate contains or transmits
moisture (such as wood or plastic).
Peel
is concentrated along a thin line at the edge of the bond
where one substrate is flexible.
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