Page 48 - Handbook of Adhesives and Sealants

18 Chapter One

Several other industries are also greatly affected by adhesives and
sealants. For example, equipment suppliers specialize in producing
machinery for application, assembly, curing, surface preparation, etc.
Equipment suppliers also specialize in developing and manufacturing
the testing apparatus that can be used to measure joint strength and
processing parameters. Then, there are testing laboratories and con-
sultants who provide assistance and services to the end-user on a con-
tractual basis.

1.4 Advantages and Disadvantages of
Adhesive Bonding
This section addresses the process of choosing a method of joining.
Each joining application should be considered with regard to its spe-
cific requirements. There are times when adhesives are the worst pos-
sible option for joining two substrates, and there are times when ad-
hesives may be the best or only alternative.
Often, one must consider the time, trouble, and expense that may
be necessary to use an adhesive. For example, certain plastics may
require expensive surface preparation processes so that the adhesive
can wet their surface. Applications requiring high temperature service
conditions may call for an adhesive that requires an elevated temper-
ature cure over a prolonged period.
On the other hand, certain applications could not exist without ad-
hesive bonding. Examples of these are joining of ceramic or elasto-
meric materials, the joining of very thin substrates, the joining of sur-
face skin to honeycomb, and numerous other applications. There are
also certain applications where adhesives are chosen because of their
low cost and easy, fast joining ability (e.g., packaging, consumer prod-
ucts, large area joints).
Sometimes conventional welding or a mechanical joining process is
just not possible. Substrate materials may be incompatible for met-
allurgical welding due to their thermal expansion coefficients, chem-
istry, or heat resistance. The end product may not be able to accept
the bulk or shape required by mechanical fasteners.
Usually, the choice of joining process is not all black or white. Cer-
tain processes will have distinct advantages and disadvantages in spe-
cific applications. The choice may involve trade-offs in performance,
production capability, cost, and reliability. This section will provide
sufficient information to make such an analysis.

1.4.1 Competitive methods
A variety of joining methods can be used to provide the assembly func-
tion. Alternative joining methods include adhesive bonding, welding,