Page 515 - Handbook of Adhesives and Sealants

Selection of Adhesives 445

The degree of inspection or quality control that is available or af-
fordable may also factor into the selection of adhesive systems

11.6.3 Cost
Economic analysis of the bonding operation must consider not only
the raw-materials cost, but also the processing equipment necessary,
time and labor required, and cost incurred by wasted adhesive and
rejected parts. The raw-materials cost for the adhesive should not be
based on price per weight or volume because of variations in solids
and density of adhesives. Cost per bonded part is a more realistic
criterion for selection of an adhesive.
Satisfactory end-use properties should be more important in the se-
lection of an adhesive than cost considerations. However, end-use
properties should not be over-specified so that the cost becomes an
unreasonable burden. Where the consideration of strength and dura-
bility requirements indicate that several adhesives may do the job,
choice will then become a cost factor for the bonding process on the
whole. The following cost factors must be considered in addition to the
materials cost of the adhesive:

Efficiency of coverage
Ease of application and process equipment needed
Processing time
Cost of labor for assembly and for quality control and inspection of
completed parts
Amount of reject material due to improper storage conditions and
production difficulties
Poor bond quality
Safety and environmental considerations including waste disposal

11.7 Service Conditions

Adhesives must also be selected with regard to the type of stress and
environmental conditions to which they will be exposed. These factors
may be the most important criteria in deciding which adhesive to use.
Depending on the nature of the stress and the environments expected,
these factors could drastically limit the number of candidate adhe-
sives. The designer must be able to confidently predict all the condi-
tions that the adhesive bond will see in service. He or she must also
be able to determine the possible effects of these conditions on the
bond—in the long term as well as the short term. Detailed information