Alternate Technique for the Measurement of Surface Tension of Treated Substrates, 1990 Polymers, Laminations & Coatings Conference Proceedings

The treatment of the surface of polyethylene, polypropylene, polystyrene and other plastics to improve their wettability for accepting inks, adhesives, or other coatings has been known for years. Printing or coating on substrates of low surface tension can lead to poor adhesion and delamination, uneven coating thickness and poor printability.

The treatment of these surfaces is usually accomplished by corona treating (high intensity electrical discharge) the substrates.

This treatment causes an oxidation on the surface of the substrate. This reaction produces carbonyl, carboxyl and hydroxyl groups which are polar and thus boost the surface tension of the substrate. Corona treatment of a substrate does not follow the old adage that if a little bit is good, a whole lot is better. Excessive levels of corona treatment cause conversion of the carbonyl group to an ether group which is nonpolar thus lowering the surface tension thus lowering adhesion to the substrate surface. The problem then arises of correctly measuring this treatment level or surface tension of the substrate.