Coextrudierte

Coextrudierte, or coextruded in English, describes polymer products produced by coextrusion, a process in which two or more melts are extruded simultaneously through a common feedblock and die to form a multilayer film or sheet. The layers bond during extrusion, creating a single structure with tailored properties.

The process yields films in blown or cast form. In blown coextrusion, several polymers feed into annular dies and are drawn to a bubble; in cast lines, molten polymers are cast as a flat sheet. Layer counts typically range from a few to dozens, with micrometer-scale layer thicknesses.

Common materials include polyolefins (PE, PP), barrier polymers such as EVOH, polyamides, and polyesters, paired with tie or adhesive layers to promote bonding between dissimilar layers. Material choices depend on required sealability, clarity, heat resistance, and barrier performance.

Applications are dominated by packaging films for food and medical products, as well as specialty films for insulation or industrial uses. Coextruded films can achieve high barrier performance with thin layers compared with laminated structures.

Advantages include combining properties in a single extrusion and avoiding separate lamination steps, while limitations involve more complex equipment and process control, sensitivity to interfacial compatibility and melt viscosity, and potential defects if processing is not well managed.

Coextruded multilayer films became widespread in packaging in the late 20th century and continue to evolve with new polymers and barrier technologies.