Coextruded Microlayer Film and Sheet

Multilayer coextrusion can be used to produce microlayer films which can be designed to provide unique characteristics. Based on the optical theory for the wave length of reflected light from the normal incidence, 400 alternating layers of poly carbonate (PC) and polypropylene were coextruded with the expected result that the 25 μm film blocked over 80% of the UV light while transmitting 80% of the visible light. Ultrathin PC films (2 μm thick), made by delaminating multilayer extrusions, had DC breakdown voltages similar to solution cast films of the same thickness. Increase of the number of microlayers of PC/styrene-acrylonitrile composites resulted in improved tensile and impact strength—with a notable reduction in notch sensitivity for the latter property.