Pass Order Decides Which Effects Remain Achievable
Pass order determines surface energy, registration accuracy, recyclability, and unit scrap rates across multi-step print converting runs.
Wetting Tension
Surface Energy Metric
Quantitative measurements express the surface energy of films, coated paperboards, and polymer laminates, determining whether liquid inks, coatings, and adhesives will spread uniformly across a substrate. Expressed in millinewtons per meter or dynes per centimeter, wetting tension indicates the thermodynamic balance between cohesive forces within a liquid and adhesive forces on a solid material surface. Packaging converters measure this property using calibrated dyne test pens or optical contact angle goniometers according to standardized test methods like ASTM D2578 or ISO 8296.
Extruded polymer barriers, film substrates, and synthetic paperboard coatings require chemical oxidation or physical corona treatment to elevate surface energy above the surface tension of applied inks. Insufficient surface energy causes liquid reticulation, ink flaking, adhesive failure, and coating de-wetting during high-speed printing and converting.
Thermodynamic Measurement Methods
Calibrated liquid mixtures containing formamide and ethylene glycol monoethyl ether apply across the substrate surface in thin continuous liquid films. Technicians observe the liquid layer for exactly two seconds to determine whether the fluid film holds together or breaks into isolated beads. If the applied test fluid maintains a continuous film without contracting for two seconds, the substrate surface energy equals or exceeds that specific dyne test fluid value.
Contact angle goniometry measures the tangent angle where a sessile liquid droplet meets the solid substrate, calculating absolute surface energy through Young’s equation. Corona discharge, atmospheric plasma, or flame treatment oxidizes polymer surfaces, introducing polar hydroxyl, carbonyl, and carboxyl groups that elevate surface tension values from thirty dynes up to forty-four dynes per centimeter or higher.
Parameter Range Boundary
Structural adhesion testing measuring mechanical peel strength after complete adhesive curing evaluates mechanical bonding rather than initial liquid wetting tension. Surface roughness and porosity measurements track physical substrate topography without quantifying molecular thermodynamic surface energy. High wetting tension values do not guarantee long-term print durability if chemical compatibility, mechanical interlocking, or ink vehicle absorption parameters remain deficient.
Treated polymer films lose their elevated surface energy over time due to additive migration and polymer chain turnover during extended warehouse storage. Wetting tension measurements become invalid when applied to porous, untreated paperboards that absorb dyne test fluids through capillary action within the two-second evaluation window.