page_title: Plastic extrusion
section_title: Coextrusion
hierarchical_section_title: Plastic extrusion / Die types / Coextrusion
caption_attribution_description: English: Multi-Layer Extrusion Technology
context_page_description: Plastics extrusion is a high-volume manufacturing process in which raw plastic is melted and formed into a continuous profile. Extrusion produces items such as pipe/tubing, weatherstripping, fencing, deck railings, window frames, plastic films and sheeting, thermoplastic coatings, and wire insulation.
  This process starts by feeding plastic material from a hopper into the barrel of the extruder. The material is gradually melted by the mechanical energy generated by turning screws and by heaters arranged along the barrel. The molten polymer is then forced into a die, which shapes the polymer into a shape that hardens during cooling.
context_section_description: Coextrusion is the extrusion of multiple layers of material simultaneously.  This type of extrusion utilizes two or more extruders to melt and deliver a steady volumetric throughput of different viscous plastics to a single extrusion head (die) which will extrude the materials in the desired form. This technology is used on any of the processes described above (blown film, overjacketing, tubing, sheet).  The layer thicknesses are controlled by the relative speeds and sizes of the individual extruders delivering the materials.
  In many real-world scenarios, a single polymer cannot meet all the demands of an application. Compound extrusion allows a blended material to be extruded, but coextrusion retains the separate materials as different layers in the extruded product, allowing appropriate placement of materials with differing properties such as oxygen permeability, strength, stiffness, and wear resistance.
caption: 5 :5 Layer co-extrusion of cosmetic "squeeze" tube
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