Evaluating Surface Energy Decay in Thermal Polyurethane Film Lamination
Evaluating surface energy decay in thermal TPU lamination requires measuring polar force components to ensure bond strength before heat and pressure passes.
Plasma Discharge
Surface Activation
Surface modification utilizes plasma discharge to alter the energy profile of polymer substrates before printing or lamination. High voltage electrical fields ionize ambient gases, generating reactive species that bombard the film surface. Polypropylene and polyethylene films possess inherently low surface energy, which prevents reliable ink wetting and adhesive anchoring.
Treating the web increases the dyne level by oxidizing chemical bonds at the interface. Converting lines apply this treatment inline immediately before extrusion coating or solventless lamination stations.
Contact Angle
Liquid droplets applied to a treated polymer spread rather than bead, yielding a measurable decrease in contact angle. Water or test inks quantify the degree of functionalization achieved across the web width. Converters measure surface energy in dynes per centimeter using standardized fluid mixtures.
Exceeding thirty eight dynes per centimeter ensures adequate bond strength for solvent based flexographic inks and polyurethane laminating adhesives. Insufficient power output from the generator leaves residual contamination or weak boundary layers, causing delamination during subsequent slitting or pouch making operations.
Dielectric Barrier
Dielectric discharge occurs between a powered electrode covered with a ceramic or quartz sleeve and a grounded metal roll carrying the moving web. The insulating barrier prevents the transition from glow discharge to a destructive arc, distributing micro discharges evenly across the film. Air gaps must remain tightly regulated because excessive distance reduces ionization efficiency while roller contact risks web rupture.
Ozone generation accompanies the process, requiring dedicated extraction hoods to protect operator health and prevent corrosion of surrounding converting equipment. Polymer chains crosslink within the top molecular layers of the substrate without altering bulk mechanical properties or optical clarity.