Stretched sheet strengthens PE pipeStretched sheet strengthens PE pipe

A composite three-layer polyethylene pipe boasts superior strength to conventional PE water pipes, enabling significant reduction of wall thicknesses and raw- material costs that reportedly more than compensates for higher production costs. Processor Sekisui Chemical Co. (Osaka) supplies the pipes under the brand name Eslon PE Ultra, and is exploring licensing the technology.

Sekisui''s pipes are comprised of inner and outer layers of HDPE (PE100) that sandwich a sheet of highly stretched (20- to 30-fold), highly oriented, spiral-wound Ecosurf HDPE sheet. In production of the pipe, the inner layer is first extruded, and then the sheet is wound round this inner layer. The semi-finished pipe is then fed through a special extrusion die and the final layer is extruded over. The sheet has a tensile modulus of 15 GPa, a tensile strength of 500 MPa, and elongation of just 10%.

Makoto Osuga, manager of the New Business Promotion Dept. at Sekisui''s Urban Infrastructure and Environmental Products Headquarters says, "Despite the apparent complexity of the process, it is cost effective for pipes with outside diameter of 200 mm, while 400-mm pipes are 30% lower in cost." A 200-mm Eslon PE Ultra pipe has around half the wall thickness of Sekisui''s single-layer PE pipes, and a single worker can easily carry a 5m-long pipe, easing installation.

The first commercial application of the Eslon PE Ultra material was in high-pressure piping used to pump water up a mountainside in Nagano Prefecture. The outer layer of exposed pipes will include carbon masterbatch.

Besides piping, Sekisui is developing other applications for the Ecosurf film itself. One such example is a plastic nose clamp that would replace the metal wire currently used in disposable masks and respirators. Sekisui has also developed sandwich panels reinforced with Ecosurf as a core material. The company has also used unidirectional laminated Ecosurf sheets to pultrude profiles with high flexural rigidity.

Stephen Moore [email protected]