Hollow, multi-layered plastic structures are provided comprising a layer of thermoplastic polyester material and a layer of polyethylene, the polyethylene and polyester layers being crosslinked together at their interface. A process for producing such structures which comprises charging a mold with thermoplastic polyester material, rotating and heating the mold so as to fuse and form a layer of the polyester material on the inner surface of the mold, cooling the mold to a point below the melting point of the polyester but above the melting point of a subsequently added cross-linkable polyethylene material, stopping the rotation and charging the mold with the cross-linkable polyethylene material, resuming the rotation of the mold and heating it to a temperature sufficient to fuse and cross-link the polyethylene with the polyester layer, cooling the mold to a point below the melting point of the polyethylene and removing the finished structure from the mold.