Testing the rolling tack of pressure-sensitive adhesive materials. Part II: Effect of adherend surface roughness

A novel method and custom-made apparatus for testing the rolling tack of pressure-sensitive adhesives (PSAs) and related materials were developed to measure bonding and debonding processes. The combined effects of adherend (probe) surface roughness, longitudinal load, and dwell time on bond-formation performance of five different tacky materials chosen from various application areas were studied. These materials included synthetic PSAs (acrylic tape and the hydrocolloid dressing, Granuflex®), water-remoistenable adhesive (CENTRAL®), edible wheat flour dough, and a static cling vinyl (PENSTIC®). Tack-rolling velocity curves were analyzed to study bonding and debondong processes. Each of the tested materials showed different tack behavior in response to varying probe roughness, external load, and velocity (dwell time). Surface wetting and mechanical interlocking were proposed as the mechanisms governing tack in most tested PSAs. Acrylic PSA tested on a smooth probe over a velocity range of 0.12-2.12 m/s showed higher tack values than on a rough one. A significant reduction in tack was due to restricted bond formation. Similarly, tack of Granuflex® to a smooth model skin surface showed higher values than to a rough skin surface. CENTRAL® showed typical cohesive failure when tested on silicone-coated paper. Interfacial failure and short-term bonding accounted for good tack performance on porous paper. Dough tested with aluminum probes showed cohesive failure similar to that of CENTRAL® at velocities higher than 0.2 m/s where the tack was independent of probe surface roughness. PENSTIC® adhered only to smooth glass where the tack values tended to decrease with increased velocity. Bonding and debonding processes of the various tacky materials were clearly affected by adherend surface roughness, longitudinal load, and dwell time, and could be successfully analyzed using our novel proposed method and apparatus.