this invention pertains to a method of producing a composite sheet of plastic materials by means of coextrusion . two plastic materials are matched with respect to their melt indices . these matched plastic materials are then coextruded in a side - by - side orientation while hot and soft to form a composite sheet having a substantially uniform demarkation therebetween . the plastic materials are fed at a substantially equal extrusion velocity and generally have substantially equal viscosities . the coextruded plastics can be worked after coextrusion while they are still hot and soft .