In the processing of the film, a raw material is extruded onto another film which has been made or the different kinds of films which have been made are bonded to each other to form a multilayer film, which is called a composite film.

Most of the composite film material is plastic, but can also be used paper, metal foil (usually aluminum) or fabric.

The basic requirement of the composite membrane is that there is good adhesion between layers and layers to ensure the overall mechanical properties of the package.

Composite film generally by the substrate, laminates, barrier materials, heat sealing materials, printing and protective coating and other components.

The coextruded film has most of the characteristics of the composite film, but one difference is that all the layers of the coextruded film are extruded together at the same time, so there are no other non-plastic materials such as aluminum foil and paper. The combination of the product material is relatively small, the scope of application is also small, but because the winter layer and the layer is by hot-melt combination without adhesive, so the food packaging co-extruded film health is relatively reliable.

The main characteristics of coextrusion film: good tensile properties, good surface brightness, in line with the film, a number of food film standards.