Thermodynamic Wetting and Surface Free Energy in Polyolefin Lamination
Thermodynamic wetting in polyolefin lamination demands substrate polar surface energy above 6.0 mN/m to achieve complete adhesive spreading and bond durability.
DIN 55660
Measurement Standard
Multi-part industrial testing specifications provide standardized procedures for determining the surface free energy and wettability of solid substrate surfaces through contact angle analysis. Issued by the German Institute for Standardization, din 55660 governs laboratory measurements conducted across polymer films, papers, paperboards and applied organic coatings. The standard defines testing configurations, optical goniometer parameters and mathematical calculations required to partition total surface free energy into polar and dispersive components.
Its scope applies to rigid and flexible solid surfaces, excluding porous absorbent networks where rapid capillary suction prevents stable droplet equilibrium.
Goniometric Execution
Specimen conditioning requires strictly controlled ambient temperature and relative humidity prior to optical evaluation under the Owens, Wendt, Rabel and Kaelble calculation model. Automated dosing needles deposit micro-droplets of at least two certified test liquids, typically deionised water and diiodomethane, onto the horizontal test surface. High-resolution digital imaging systems record droplet profiles within milliseconds of deposition to calculate baseline tangent angles before evaporation or chemical absorption alters droplet geometry.
The contact angle represents the geometric angle formed between the solid surface and the tangent line drawn at the liquid-vapour interface. Pure water probes polar functional groups such as hydroxyls or carboxyls, while non-polar diiodomethane measures London dispersion forces present within the substrate chemistry.
Converting Evaluation
Board grades undergoing corona, plasma or flame treatments are assessed against these standardized values to verify functional receptivity for inks, varnishes and adhesives. Aqueous flexographic printing on folding boxboard requires polar surface energy values exceeding thirty-eight millinewtons per metre to ensure uniform wetting and film consolidation. Insufficient total surface energy or an unbalanced polar ratio leads to pinholing, crawling and poor mechanical bonding of UV-curable overprint varnishes.
Laboratory testing under this standard resolves disputes regarding adhesive failure along glued carton manufacturer seams. The numerical surface energy value derived from the test protocol serves as an absolute threshold for verifying adhesion reliability across commercial printing operations.