Pressure Sensitive and Remoistenable Adhesives

For labels and tapes, where the adhesive is commonly applied to one of the adherends and then much later used to affix that substrate to another, such as a container, it is common to classify labels as either remoistenable or pressure-sensitive. 

Remoistenable adhesives are applied as water-borne adhesives and then dried. When dry, they have little or no tack. To apply the tape or label to the box, bottle, or other package structure, water must be applied to reactivate the adhesive. Then the full strength of the bond will develop as the water is removed. Such adhesives are commonly used for adhering paper to paper or to other materials. 

Pressure-sensitive adhesives are applied from a liquid base, usually as hot-melts, and retain tack when they are cool and dry. To keep pressure-sensitive labels and other components from sticking to something before they are supposed to, they generally remain on a carrier web until they are ready to be applied. The carrier web is coated with a material that provides easy release, usually a silicone. 

A variety of different pressure-sensitive formulations are available, many of which have already been mentioned. Some formulations provide permanent adhesion. 

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