Abstract: Methods for co-extruding multiple layers of materials, in particular high viscosity elastomer materials, wherein the method allows the use of either rheologically matched or unmatched elastomers. Devices for practicing the methods are disclosed. Multilayer extrudates exhibiting desirable performance can be formed from materials including high and/or low viscosity elastomers.

Abstract: Traditionally, the rheological properties, including, for example, the viscosities, of two or more polymers that are to be co-extruded must be well matched in order to obtain acceptable multilayer structures. This limitation severely narrows the processing window for such co-extrusions as well as the combinations of polymers that can be used in such co-extrusions. The technology disclosed herein removes these limitations and allows for the co-extrusion of a wider variety of combinations of polymers, even when the rheological properties of the polymers to be used are significantly different, while still providing acceptable multilayer structures. Stated another way, the technology disclosed herein improves the multilayer structures that can be obtained when processing two or more polymer materials with significantly different rheological properties via layer-multiplying co-extrusion.