The paper and packaging industry is one of the largest users of adhesives [Fig. 1]. Adhesives used in paper and packaging can be divided into two main types:
hot melts. Which type of packaging adhesive to use in an individual case depends, among other things, on the material to be bonded, the production equipment and the end-use demands on the bond.
- water-based systems like dextrins, starch or emulsion adhesives, and
- hot melts. Which type of packaging adhesive to use in an individual case depends, among other things, on the material to be bonded, the production equipment and the end-use demands on the bond.
Sometimes waterborne adhesives are the better solution. At other times, hot melts are the adhesives of choice. Both types contain a polymer that is responsible for the cohesion, or internal strength, of the adhesive. The required wet-out and penetration are achieved by dissolving or dispersing the polymer in water, or by melting it into a liquid form. The adhesive is returned to a solid condition by removing the water by absorption or evaporation, or by cooling the melt. In both cases, it is a physical process that is responsible for building strength in the glue line.
Reactive products are also used, but only for some special applications such as bookbinding.