In extrusion coating melted polymer is extruded onto existing sheets or films prior to passing through the calander. The starting sheet or film material can be regarded as a carrier and may be another polymer, cardboard, (non-)woven fabrics, metallic foils/sheets, or paper.

Multiple layers may be formed by extrusion coating on both sides of the primary film or carrier. Alternatively, a multilayerstructure can be created by introducing several extrusion coated layers. Coextrusion can only be used for polymers with similar processing conditions. Deviating processing conditions particularly in case of substrates that are incompatible with other materials such as metals or paper, extrusion coating is the only choice.