Tack
Definition
Bonding force generated the instant tape contacts the adherend under light pressure.
Historical Background
1970s: inclined plane ball tack test replaced subjective finger-touch method.
Example
Instant adhesion = good tack; repeated pressing needed = poor tack. Like love at first sight.
Formula
Initial Tack = Steel Ball Mass (g) / Steel Ball Rolling Distance (mm)
Core Concepts
Surface wetting speed: whether adhesive molecules instantly fill micro-voids, depending on Tg and coating weight.
Extended Applications
Express labels: high; automotive tinting: low (repositioning); medical: moderate; electronic labels: high (rapid fixation).