Abstract: Device for joining of tubular parts (10, 11) made from plastic, especially polyvinylidene fluoride, polypropylene or polyethylene, in which aligned parts (10, 11) exhibiting about the same diameter are pushed together and are welded on abutting surfaces (12, 13) by effect of heat. Abutting surfaces (12, 13) of tubular parts (10, 11) in the direction of the inside pipe space are undercut or recessed so that the edge formed by inside surface (15) of tubular part (10, 11) and the abutting surface springs back opposite the edge formed by outside surface (18) of tubular part (10, 11) and abutting surface (12, 13), and so that parts (10, 11) in the area of abutting surfaces (12, 13) in the axial direction essentially are softened equally deeply, then pushed together and, as a result, are welded together. Especially wherein the heating element (20) consists of a fixed disk (23') and a heating ring (23") of metal with a PTFE-ring (21') which may be additionally fixed.

Abstract: An extrusion and calendering method is provided to produce a plastic panel, in particular for the lining of concrete containers, having strongly undercut anchoring elements. These protrusions preferably include flat-shaped wings which are arranged approximately V-shaped, forming an angle with and being offset in their width from each other. The leading wing upon the manufacturing process has a smaller angle to the normal through the panel base. The wings may also, differing from the rectangular cross sectional shape described, have a round, oval, elliptical or square cross section.