About Adhesives...

Q:
When applying a label, what is the difference between a high energy surface and a low energy surface?
A:

Adhesion is defined as the molecular force of attraction between two surfaces. The strength of that attraction is influenced by the chemical and electrical forces between the molecules, as the two surfaces come together. Adhesive strength is directly proportional to the surface area of the interface between the two surfaces. The more similar the chemical structure of each surface is to that of the other, the higher the affinity they have toward each other, the higher the surface area will be, resulting in stronger adhesive forces. Remember that this is not the only factor which influences an adhesive bond.
Using a drop of water as an example will help you understand these phenomona, . Water has a "high surface tension", i.e. is a high energy liquid. It will want to spread uniformly over other high energy surfaces, because of the forces discussed above. Water "sheeting" over clean glass from the freshly washed glasses in your dishwasher is the result. However, water does not spread well over a low energy surface, hence the beading of water on your freshly waxed car. In summary, the strongest adhesive bonds are achieved when a high energy adhesive is bonded to a high energy surface, and a low energy adhesive is bonded to a low energy surface. Weaker adhesive bonds result if either is interchanged (i.e. high energy adhesive on a low energy surface). As a reminder, the reason that a pressure sensitive label can be easily removed from its liner is because trhe silicone coated liner is a very low energy surface, laminated to the relatively higher energy surface of the adhesive layer.
Examples of high energy surfaces include: clean, dry, glass, metal, painted surfaces. Low energy surfaces would include: waxy, oily, Teflon or silicone surfaces.

Q:
When should I use a silicone adhesive instead of an acrylic adhesive?
A:
All of our standard label materials typically use an acrylic pressure sensitive adhesive. Silicone adhesives are thermally more stable than are acrylic adhesives. Polyonics offers two Polyimide products with silicone adhesive (XF 546 and XF 594, respectively) for those applications that require a label material to perform beyond the range of acrylic adhesives. Remember that silicone adhesives are also more expensive than acrylic adhesives.
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