4.3.5 Surface Preparation: Chemical Activators

There are several methods to artificially (but temporarily) increase the surface energy to prepare low-energy surfaces for bonding. First, primers may be used to increase adhesion or reactivity of adhesive products on these surfaces. Second, corona or plasma treatments may be used to increase the surface energy (Figure 94). The amount of increase in energy is often related to the intensity of the treatment, the proximity of the treatment device to the surface and the amount of time the surface is treated.

Activators are often confused with primers, but where primers (and all other surface preparation) affect the substrate surface, the role of an activator is to work directly with the adhesive. Activators carry a chemical component necessary for the adhesive to cure or increase its cure speed. As a surface preparation, they may be applied to one surface and the adhesive applied to the other. In some cases, as for anaerobic adhesives that require active metal to cure, the activators add active metal ions to inactive surfaces, such as stainless steel. Some two-part mixed adhesives have an ‘activator’ component, but these are mixed before application and not applied alone to surfaces. Similar to primers, activators designed for one type of adhesive may not be suitable for another type.