For many applications, such as flexible packaging, the use of a single material may not satisfy all of the properties demanded of the product. In these cases, a composite consisting of two or more layers of material may provide the desired performance. A particularly common means of creating such a composite is to laminate various polymeric films to other films, foils, papers, etc. with a polymeric adhesive.
This production solution is commonly employed in the packaging industry where the end-products require multi-functional properties, such as high tensile strength and high gas permeability. The laminate construction can become rather complicated due to the nature of the specific application. A typical laminate used in the medical packaging industry, for example, may be a multi-layer composite containing films of polyester / polyethylene / metal foil / polyethylene.
Laminating adhesives are available in a variety of technologies, viscosities, and solids concentrations. There are four basic categories of laminating adhesive that are commonly used.