Bond Performance Variables

(Courtesy of 3M)

If after considering the joining alternatives, adhesive is selected for further evaluation, bond performance can be envisioned as the seat on a three-legged stool with adhesive, substrate, and bonding process as the interacting legs (see figure 1). The types of stress exerted on the stool also need to be considered. There will also be a price for bond performance, which is not just the cost of adhesive, but the total applied cost.


 

This “in-place” cost should be the basis for an economic comparison of different adhesives (as well as other joining methods).

Adhesive characteristics include cure kinetics, viscosity, surface energy, and more. Substrates have to be considered in such terms as shape, flexibility, strength, surface energy, and, as now known, process history. The consideration of bonding process involves application or dispensing technique, adhesive coverage, and more.

How well the adhesive wets the substrate is an example of the interaction between adhesive and substrate. The rate of adhesive viscosity build up on the substrate is an example of an adhesive/bonding process interaction. In examining the substrate/bonding process interaction, factors such as substrate cleanliness and roughness are considered.