Role of Corona Discharge Treatment on Improving Polyethylene/Aluminum Adhesion - An Acid/Base Perspective, 1992 Polymers, Laminations & Coatings Conference Proceedings

Varying levels of corona discharge were applied to the surfaces of extrusion coated low density polyethylene (LDPE) and aluminum foil. The adhesive strength between the two substates was improved as a result of the corona surface treatments.

The effects of corona discharge treatment on the surface chemistry of aluminum foil were characterized using Flow Microcalorimetry. The LDPE and aluminum foil surfaces were also characterized by measuring the contact angles of neutral water, methylene iodide, and of acidic (pH 2) and basic (pH 12) aqueous solutions.

The neutral water and methylene iodide contact angles measure the polar and dispersive components influencing the surface tension changes arising from corona treatment. Only the polar component was affected by the corona treatment; the dispersive component was unaffected.

Contact angles of high and low pH solutions were used to relate the changes in surface polarity to increases in acidic or basic surface sites introduced by the corona treatment. These measurements indicated that while both acidic and basic groups were introduced, increasing levels of corona treatment produced greater acidic character on the foil and LDPE surfaces.

Flow Microcalorimetry (FMC) studies of the interaction of acidic and basic surface probes with the foil surfaces lead to the same conclusions as the contact angle studies. The increases in acidic and basic sites on the surfaces of the treated and non-treated foils and LDPE films were then related to the increased adhesion between the two substrates.