- Contact adhesives are applied using the two-sided contact method, i.e. the adhesive is applied to both bonding surfaces.
- Contact adhesives are usually solvent-based. In addition, they contain polymers that function as binders.
- After evaporation of the solvent, these polymers – above all polychloroprene and polyurethane – change from the amorphous to the crystalline state.
- Pressure-sensitive adhesives remain elastic after drying and are therefore particularly well suited for materials where a flexible bond is desired, e.g. shoe soles or leather belts.
- They are also suitable for bonding dense materials that are impervious to solvents.
- Contact adhesives find widespread use in large-surface applications, e.g. coating tables with high-pressure laminates (HPL).
- They can also be used for all types of wood bonding, for combination bonding with stone, concrete and rigid PVC as well as for applications that involve flexible materials.
- Contact adhesives are applied to both parts to be joined. This is done by spreading a thin, uniform layer of adhesive to both surfaces.
- During the evaporation time, which may differ depending on the solvent, the parts are left to dry in the open air until the adhesive films feel "touch-dry". They must no longer be stringy and have only little instant tack.
- Now the parts to be joined are carefully aligned and briefly pressed together with high contact pressure. After first contact, adjustments to the position are no longer possible.
- Not the duration but the intensity of pressure (compressive force) is essential for the bonding strength. It causes the two not yet crystallized adhesive layers to coalesce and finally solidify.
- The parts to be joined instantly adhere to each other and the workpiece is quickly able to resist mechanical stress. If contact bonding is properly done, the position of the parts can no longer be adjusted.
- Final strength is reached when the residual solvents have evaporated from the glue joint, usually after a couple of days.