Materials useful for fabrication of backing layer 18 include high modulus polymeric materials such as polyamides as for example aramids, nylon-66, nylon-6 and the like; polyesters such as polyethylene terephthalate polybutylene terephthalate, and the like, acetal; polysulfones; polyethersulfones; polyacrylates; acrylonitrile/butadiene/styrene copolymers; poly(amideimide); polycarbonates; polypheny