The three main types of packaging adhesives are water-based, solvent-based and hot-melt adhesives. Of these, water-based and hot-melt systems are gradually edging out solvent-based systems as adhesive manufacturers strive to reduce volatile organic compound (VOC) emissions and improve air quality.
For packaging applications, water-based adhesives are the most widely used. In addition to air-quality benefits, water-based adhesives offer the advantages of strength, low cost, energy efficiency, ease of use and safety. Water-based adhesives are available in both natural and synthetic variants. Natural ingredients include animal- and vegetable-derived materials like starch and animal glue.
Synthetic water-based adhesives are usedâincreasingly in place of natural water-based adhesivesâto label containers, make composite cans and form and seal cartons and cases.
Use of hot-melt adhesives for packaging applications continues to grow, primarily for automated carton and case sealing. This type of adhesive is 100 percent solid; it contains no solvent or water. On the packaging line, a dispensing system applies the adhesive to a substrate such as paperboard, rigid polyethylene or film-laminated material. The hot-melt adhesive dries quickly after application, forming a strong bond between the joined surfaces.
Because hot-melt adhesives dry so quickly, they are most suitable for high-speed operations. This type of adhesive also can be formulated for use with a range of packaging materials, though any substrate that is sensitive to heat is a poor candidate. Processes that expose the hot-melt bond to high temperatures also are not appropriate, as the heat can cause the adhesive to melt and the bond to fail.