Mieke Vanhoof, Cynthia Teniers
Papers # 2016 Berlin
Since many years EVOH (ethylene/vinyl alcohol copolymer) is applied in plastic heating systems [cross-linked polyethylene (PEX), polyethylene of raised temperature resistance (PE-RT), polypropylene (PP), polybutylene (PB)], where its excellent gas barrier properties ensure a minimization of corrosion of the metal parts in the heating system. Such multilayer pipe structure are also commonly used for domestic gas supply systems. There are however several other pipe applications where the incorporation of an EVOH barrier layer by coextrusion is beneficial: fuel transport systems, drinking water systems for contaminated soil and pre-insulated pipe systems. In these applications, in addition to gas barrier, the fuel vapour barrier and chemical resistance of EVOH are of particular interest.
Since many years EVOH is applied in plastic heating systems (PEX, PE-RT, PP, PB), where its excellent gas barrier properties ensure a minimization of corrosion of metal parts in the heating element. Such multilayer pipe systems with an EVOH barrier layer are also commonly used for domestic gas supply systems.
There are however several other pipe applications where the incorporation of an EVOH barrier layer by coextrusion is beneficial: fuel transport systems, drinking water systems for contaminated soil and pre-insulated pipe systems.
Areas around fuel stations have an increased risk for hydrocarbon contamination of the soil and the ground water. By adding an EVOH barrier layer to the fuel transport pipe systems, the level of environmental protection can be increased, avoiding expensive future remediation costs.
Especially in areas with a high population density, there is increasing pressure to reuse former industrial land that may be contaminated. As such “brownfield” sites are redeveloped, it is necessary to ensure the quality and safety of drinking water supplies that may be laid through them.
Drinking water pipes with an EVOH barrier offer a reliable, full plastic solution that can substantially decrease the migration of hydrocarbons, volatile organic compounds (VOCs) and organic solvents from contaminated sites.
Pre-insulated pipe systems, insulated with rigid polyurethane (PUR) foam, are used for district energy networks as well as other industrial applications such as oil & gas networks. Studies have shown that the service life of these pre-insulated pipe systems can be shortened by oxidative degradation of the PUR foam which can endanger the structural integrity of the pipe system. In addition, the insulation efficiency of these pre-insulated pipe systems reduces over time as outside air diffuses into the foam cells, leading to higher energy loss. Pre-insulated pipes with an EVOH barrier in their casing pipe are not prone to oxidative degradation, and retain their insulation efficiency throughout their lifetime, significantly reducing the operating costs of the overall network.