Suitable polymeric compositions for the first layer include, by way of illustration only, polyolefins, especially polyethylene and copolymers of ethylene and one or more of such monomers as vinyl acetate, acrylic acid, methacrylic acid, acrylic acid esters (acrylates), and methacrylic acid esters (methacrylates); copolymers of ethylene with such vinyl monomers as vinyl alcohol, vinyl chloride, and