Hojer, Janson, Oderkerk, Venator
# 2006 Washington DC
For nearly three decades two technology processes have been available for production of PEX piping by moisture induced silane crosslinking (PEX-b). The first technology, the Sioplas™ process, was invented and patented by Dow Corning. This process requires extruding pipe from a reactive compound composed of silane groups which have been grafted onto polyethylene (PE) polymer chains by the addition of organic peroxide in an offline compounding process. The second technology, the Monosil™ process, was developed by Maillefer as a one-step-process where all of the components of PE base resin, additives, peroxide and silane are grafted in a specialized compounding extruder which also extrudes the pipe in-line. This paper describes a new innovative technology process that offers the PEX pipe industry a third choice in materials for producing PEX-b piping. The Vinyl Silane Copolymer or Visico™ process, invented and patented by Borealis AS, copolymerizes the silane directly into the PE polymer chain during the polymerization process. This ensures an excellent homogeneous distribution of the reactive silane sites and avoids the heavy use of organic peroxides needed by the other PEX-b technologies to graft the silane component. The resulting product offers greater process stability and higher purity for superior taste & odor performance in PEX piping. All of these technologies require post treating the pipe with steam or hot water to induce the crosslinking reaction and produce PEX-b pipe although the new Borealis Ambicat™ catalyst system for MDPE PEX-b radiant heating pipe enables crosslinking to take place during pipe storage at ambient temperatures by absorbing moisture from the surrounding air in the warehouse or yard.
