A coextrusion process is typically a technique to extrude two or more materials via single die. Here, two or more orifices arranged in such a fashion so as to merge and weld the extrudates together into a single laminar structure before the process of chillin. Each single material is fed to the die from different extruder. The orifices are arranged in a manner, so that each of the extruder is in a position to supply two or more plies of similar material. Co extrusion is mostly used in film, sheet, along with tubular extrusion application. An example of aluminium strip that is co extruded with HDPE is shown in the following image.
Advantages of Co extrusion Process
Combining rigid and flexible material is able to exploit the different and individual strengths of each material in to a single product. Another advantage is that it permits multicoloured products. This can range from decorative finishes to even product identification. As discussed the basic advantage of a Co extrusion process lies in the fact that it is possible to impart a desired distinct property. This could be in terms of:

• Stiffness
• Resistance to chemicals
• Impermeability
• Heat-sealability

Applications of Co extrusion
The Co extrusion process is a widely used technique these days, producing many products for critical industrial applications. To understand the importance of co extrusion let us consider a very simple example of a striped drinking straw. It is a perfect example of a coextruded tube. For example, a white straw gets extruded from polypropylene, a colored polypropylene material could be coextruded in a smaller area for creating a striped tube.

A relatively new application is the Co-extruded plastic films. These are having a wide use in packaging industry. Another emerging sector for co extrusion is the industrial films and laminations. The medical industry is another area where co-extruded tubing products are used. Further irrigation devices as used in the agricultural industry has a great use for co extruded stripes.

Co Extrusion Process in Medical Industry The coextrusion process is providing considerable service to today’s medical device market. Coextrusion is combining multiple materials to enhance a product’s properties. Changes include better chemical resistance, excellent mechanical attributes, improved visual and aesthetic appearance, along with reduced cost. Multilayer Tubing is a great example of Coextrusuion process that has extensive use in medical industry. Another example of co extrusion process used in Medical industry is the Stripes. Co extruded stripes are often used as identifiers in medical applications.

Buyers consideration in Co extruded Profiles
Co extrusion is not an easy process, as newer materials continue to be formulated invariably this will lead to complexities in a buyers decision. Certain points that are listed here may help you to zero down on the best products.

• Classification of needs
  Before deciding on the contractors first and foremost need is to list down the things that they need from the contractor. This may include whether or not value added services are provided, or the type of finishing options etc.
  
  
• Knowledgeable contractors
  First and foremost consideration find a contractor that has an experienced and innovative staff. Narrow down on those contractors who are willing to work with OEMs and develop custom solutions, that includes process control and side by side new product developments.
  
  
• Close Cooperation
  The contractor should show a tendency to work in close cooperation with the suppliers of resin. This helps to keep abreast of the latest developments and newest materials. Further, the contractor should show the capability for optimizing material selection through the option of multiple trials.
  
  
• Thorough Understanding
  A contract manufacturer dealing with co extruded profiles should show the inclination to listen to the buyer and thoroughly understand its needs. Once the contractor understands the needs, it should then be able to translate the requirements directly into a product specifications. Further there must be a proper briefing of how its engineering resources is going to ensure that the manufactured product exactly meets the specifications asked for.