Coating Adhesion - To Stick or Not To Stick?

Posted on 7/14/2014 12:18:36 PM By ASC

On a recent entry of the Converting Quarterly vacuum web coating blog, Dr. Charles Bishop and Prof. Steven Abbott dispel myths and answer questions about adhesion. The first point is that surface energy is not the same as adhesion. The two are often correlated with increased surface energy leading to increased adhesion, but this is not always the case and depending on potential bonding sites a compound can have high surface energy and very good or very poor adhesion. A key requirement for strong adhesion is a direct bond between the adhesive coating and the substrate, which includes at least three points of entanglement for the bulk polymer chain. Entanglements that involve only surface side-chains of the polymer will not be as effective. Finally, strong adhesion requires some mechanism to absorb energy, such as the energy applied when testing the bond. Prof. Abbott suggests that an amorphous surface for the polymer may stretch and create a stronger adhesive. However, this approach is not in common use at this time. Prof. Abbott has a website, Practical Adhesion, with apps on adhesives and barrier calculations.