A Novel Material for Plastic Pipe Applications [PE]

This paper describes the process and modification of a standard class PE100 high-density polyethylene pressure pipe grade polymer to a class PE200 grade polymer, for the manufacture of thermoplastic pipes for both liquid and gas conveying. This modified polymer was developed through the collaboration of Ion Beam Applications (IBA) and Gammatron, and has recently been introduced to the market under the trademark Raprex™. This paper details the technical developments that took place and the particularly promising results that have been achieved. The hydrostatic stress strength, expressed as hoop stress at ambient temperature and 100°C, of pipes made from the modified high-density polyethylene is particularly high – at least double that of the non-modified polymer. This implies that pipes may be manufactured from the modified polymer with reduced wall thicknesses, which will continue to meet hydrostatic stress strength requirements while achieving a cost and weight savings advantage. The uniqueness of this new material lies in the prior modification of the feedstock highdensity polyethylene polymer by the partial radiation cross-linking of the feedstock material. The advantage is that the pre-cross-linked material can be processed on existing extrusion equipment with little modification required. Apart from the remarkable increase in the hydrostatic stress strength of this new material, increases in other mechanical properties, as well as resistance to chemicals, have been achieved making this material a candidate for a variety of different pressure and non-pressure pipe applications. Furthermore, the polymer and additives used are all suitable for use in contact with water intended for human consumption and are fully recyclable with the associated positive environmental implications.