Coextrusion
Coextrusion is the simultaneous extrusion of multiple layers of material. Two or more extruders melt and deliver a steady volumetric throughput of different viscous fluids to a single extrusion head (die), which will extrude the materials to form layered products. The extruders are connected to a shaping system for the melt consisting of an adapter, a feedblock, and a die. The feedblock distributes the melt streams to the die for forming multilayer structures. Some systems do not use feedblocks and use only multicavity dies. (Mount and Oliver 8/4/2010)
Go to Mount and Oliver article, “Film and Sheet Dies and Co-Extrusion Feedlblocks and Dies
Coextrusion is followed by any of various processes, such as thermoforming or blow molding, to fabricate a variety of multilayer products. Each layer provides a separate function or property, such as a barrier, mechanical strength, appearance, cost reduction, or printability. If adhesion between different layers is poor, a tie layer between these layers can be added. However, design and optimization require a realistic understanding of steady-state viscoplastic fluids in coextrusion flows. These fluids are viscoplastic with a yield stress and wall slip during flow. This behavior makes the design of hardware and optimization for coextrusion difficult. Experience has shown that interfacial stability is an important issue. Kalyon, Polym. Eng Sci., 50 #4, p 652-664 (2010)
Coextrusion Automotive
Coextrusion Foams
Extrusion
Processing
Recent US Patents
3/1/2011
7,897,081
Method of extruding articles
Ausen, Seth and Venne of 3M, Minnesota, have developed a method for coextruding an initial melt stream through a profile die. The die insert is positioned so as to cause redistribution of at least a portion of the melt stream. (RDC 9/12/2011)
8/10/2010
7,771,805
Low organic vapor permeation resin composition
Negandhi and Zhu of Ovation Polymer Technology have developed a material for gas tanks based on coeextruding a polyphthalamide with other polyamides, polyesters and other modifiers with improved barrier properties, impact strengths and heat distortion temperatures. This is used in gas tanks for gasoline engines such and lawn mowers and other garden machinery. (RDC 10/12/2010)
6/29/2010
7,743,538
Extruded plastic u-channel sign post covers
Parenti of Ideal Shield has developed covers for U- or C- channels for sign posts consisting of overlapping walls. The front wall includes a co-extruded reflective, fluorescent, phosphorescent or colored lengthwise strip of material to enhance visibility. (RDC 10/12/20100)
3/16/2010
7,678,316
Coextruded profiled webs
Ausen, Venne, Seth have developed a coextrusion process based on an oscillalting, profiled die plate resulting in a peak and valley structure and partitioning of the resins with side-by-side zones of different resins. (RDC 10/12/2010)