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INTRODUCTION AND GENERAL CONSIDERATIONS
In the process of joining two parts by means of anadhesive, the
adhesive must at one, tirne'exist in the liquid state between the two
surfaces in order to properly wet them. Subsequently, the adhesive
'mustbe solidified to impart strength to the bond. This can be done
in many different ways:
In solvent borne adhesives, the adhesive is applied'asa solution,
the solvent is removed by evaporation. Similarly, water borne adhesives
contain the' adhesive material as a dispersion or, a solution and set
upon removal of the water. Hot melts are applied in the molten state'"
and solidify by cooling down. Reactive adhesives use one or more low
molecular weight reactive liquids, which undergo a polymerization
reaction, frequently accompanied by chemical crosslinking.
Reactive adhesives generally qualify as high quality products'leading
to high bond strengths with good stability. .They suffer from several
disadvantages however: two component materials require mixing and
.'once they are mixed, they must be'used within a short time (socalled
"pot life"). One component, reactive adhesives most frequently cure,
by reaction with moisture and tend to have a limited shelf life. Most:
reactive adhesives tend to, require a relatively long time to complete,
'the curing' reaction, which is inconvenient if'not unacceptable for.
; industrial, bonding.
