a weatherseal or belt - line seal for a vehicle is formed by extrusion of an olefin - based thermoplastic elastomer or vulcanizate as an elongate body of arbitrary length and cross - section . the cross - section is adapted for use in a particular location in the opening of a structure to be protected against wind and rain , for example around the glass of a window in a vehicle &# 39 ; s door , or around the opening in which the door is closed , so as to present at least one sealing surface against which the glass or door may be abutted to provide a seal against the elements . a slip - coating is co - extruded onto one or more longitudinal sealing surfaces of the body ; the slip - coating contains a novel compatibilizer which allows thermoplastic polyurethane to be chemically bonded to a graft copolymer of polypropylene and a compound having two anhydride groups . the reaction product of the grafted pp and the tpu effects a thermal bond with the sealing surface of the body . the slip - coating has a combination of softness and abrasion resistance which are uniquely suited for the purpose of the weatherseal .