Page 322 - Handbook of Adhesives and Sealants

Adhesive Classifications 283

Figure 8.1 Some possible molecular structures in poly-
meric resins used as adhesives. 1

moderate contact pressure. Thermosetting adhesives are sometimes
provided in a solvent medium to facilitate application by brush or
spray. However, they are also commonly available as solventless liq-
uids, pastes, and solid shapes. Epoxy and urethane adhesives are ex-
amples of common adhesives that are in the thermoset chemical fam-
ily.
Thermosetting adhesives may be sold as multiple or single part sys-
tems. Multiple part systems have their reactive components sepa-
rated. They are weighted-out and mixed together at the time of ap-
plication. Multiple part adhesives generally have longer shelf lives,
and they are usually cured at room temperature or more rapidly at
elevated temperatures. Once the adhesive components are mixed, the