Polyurethane Tactile Film Surface Chemistry and Abrasion Dynamics
Polyurethane tactile films trade high material costs for self-healing elastomeric scuff resistance, requiring precise thermal nip control and high dyne levels.
Adhesion Failure
Interfacial Cleavage
Physical separation occurring at the boundary between an applied coating or ink film and a paperboard substrate marks the loss of mechanical and chemical bonding across the contact plane. Converting lines encounter adhesion failure when surface tension differences prevent complete wetting of the extruded polymer or cured ink system. Measurement relies on standard tape peel tests or cross-hatch pull testing performed at specified intervals after drying or cooling.
This phenomenon applies strictly to boundary cleavage between distinct material layers and excludes internal fiber tearing within the paper matrix itself.
Mechanical Stress
Interfacial stresses build up during drying or cooling cycles as liquid coatings shrink or polymer extrudates cool at rates different from the fibrous base. High tension on converting lines accelerates interfacial separation when the flexural stiffness of the board forces the coating layer to shear away at folding creases.
Bond Boundary
Surface contamination from residual release agents or migratory fatty acid amides on recycled board stocks lowers the surface energy below the threshold required for durable chemical bonding. Low surface energy prevents liquid coatings from spreading, which starves the contact plane of physical anchors. Corona treatment units increase surface energy through surface oxidation, yet excessive oxidation degrades the top cellulose fibers and causes delamination directly beneath the surface.
Cold temperature storage further weakens mechanical interlocking by hardening elastic polymers, forcing the dried film to snap away under minimal shear force.