Abstract: A crosshead (10) and a method are provided for extruding a tubular layer of a thermoplastic material, or for coextruding tubular layers of various thermoplastic materials, without incurring a weld line in any of the layers. The crosshead (10) includes a supply passage (42), a distribution passage (46) which provides an annular flow of thermoplastic material around a mandrel (18) by providing separate flows that merge distal from the supply passage (42), a mixing passage (110) which serves as a first static mixer by dividing the stream of thermoplastic material into a plurality of streams (96) and subsequently merging the divided streams, and a forging passage (118) which serves as a second static mixer by compressively forging that thermoplastic material into a cross section of increased area prior to extruding the thermoplastic material through a die opening (38).

Abstract: This invention relates to a plastic or thermoplastic container designed to exhibit non-paneling of its sidewall due to reduction in pressure within the container. The container itself is provided with a yieldable bottom endwall especially constructed to compensate against the effects of reduced internal pressures often experienced after sealing hot fluids and the like. The thermoplastic container herein described is capable of being filled and sealed without paneling or deformation of its sidewall, said bottom endwall being displaceable inwardly, in preference to the sidewall, upon a relative reduction of pressure in the container, said bottom endwall comprising an outer frustoconical surface extending downwardly and inwardly from said sidewall toward the longitudinal axis of the container at an angle between about 5.degree. and 30.degree.