Epoxy resin adhesives are supplied as two tubes that must be mixed before use because
- A. one tube contains the solvent that evaporates
- B. the two components are the same substance at different concentrations
- C. mixing lowers the temperature of the joint
- D. the resin and the hardener react together to form cross links, setting the adhesive
Explanation
Setting is a chemical reaction between the resin and a hardener that builds a rigid cross linked network, so the two must be kept apart until the moment of use. Because no solvent has to evaporate, epoxies set even in a sealed joint and bond metals, glass and ceramics strongly. Adhesives that set by solvent evaporation, such as rubber cement, work on a quite different principle.