Hot Melts Hold Fast

After laminating, the silicone and adhesive interface may need time to complete the wetting process. With full contact at the interface, van der Waals bonds will develop and contribute to the release force, although the development of these bonds can be delayed due to rotation and reorientation of the silicone and adhesive polymers. Also entanglement of these polymers at the interface can occur over time. After days or weeks, the orientation processes should be complete, although further increases in release may develop due to the chemical reactions that bridge the interface. Investigating the hot melts with the three curing variations points to possible causes of these interactions.

Graph 1 shows the release properties of all nine adhesives, each laminated onto a release liner cured with a high dose of UV light. Higher release forces (y-axis) indicate stronger adhesion. While different applications will demand different requirements, stability over time is what is most important. The data indicate that all the hot melt variations are compatible with RC silicones cured at high-dose UV. Orientation and rotation effects are noticeable with adhesives number 7, 8, and 9 at the beginning of the aging test, but effects stabilize after some days.

A similar performance was observed on the silicone liner cured with the low UV dose (Graph 2). Both low- and high-UV dose liners yield comparable release stability, and excess UV does not harm release performance. Of course, a minimum UV dose is needed for full cure of the silicone layer. Typically, it is recommended that line speed not exceed 200 m/min. when running only a single 120 W/cm UV lamp.