Extrusion Dies Industries (EDI) has introduced an innovation in flat extrusion die systems that makes it possible to multiply key functional layers in cast film and sheet, ’’substantially improving properties without increasing either overall thickness or raw material content“.
The new ’microlayer’ technology is said to enable extruders to achieve increases in impact strength, elongation, oxygen and moisture barrier, and other properties.
The key to the improvements is special tooling developed by EDI to implement a coextrusion process designed and patented by Dow Chemical. Called a ’layer multiplier’, the flat die system transforms a typical sandwich structure from a standard coextrusion feedblock into a structure in which one or more of the layers has been subdivided into multiple microlayers. The overall thickness of the resulting coextrusion is said to be no greater than if the original sandwich structure had been transferred directly from the feedblock to the extrusion die, without the intervention of the layer multiplier.
Gary D Oliver, EDI’s vice-president of technology, remarks: “Without adding even a tiny increment in the amount of barrier resin used for a given volume of product, this proliferation of layers creates synergistic effects that reduce oxygen ingress from three to five times in comparison with a conventional barrier coextrusion”.
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