In order to extend the shelf life of food, medicine and other materials, many of the food and drug packaging materials now use multi-layer co-extrusion composite films. At present, there are two, three, five, seven, nine, and even eleven layers of composite packaging materials. Multi-layer co-extrusion film is a film that extrudes a variety of plastic materials from a single die at the same time through many channels, which can give play to the advantages of different materials.
Multi-layer co-extruded composite film is mainly composed of polyolefin. At present, the structures that are widely used include: polyethylene/polyethylene, polyethylene/vinyl acetate copolymer/polypropylene, LDPE/adhesive layer/EVOH/adhesive layer/LDPE, LDPE/adhesive layer/EVOH/EVOH/adhesive layer/LDPE. The thickness of each layer can be adjusted by the extrusion process. By adjusting the thickness of the barrier layer and the use of a variety of barrier materials, the film with different barrier properties can be flexibly designed, and the heat sealing material can also be flexibly changed and allocated to meet the needs of different packaging. This multilayer and multi-function co-extrusion compound is the mainstream direction of the development of packaging film materials in the future.