Abstract: The present invention provides an improved system for the biaxial expansion of polymeric pipe. Wherein the system comprises a tie bar, mandrel, and cooling system. In use, the polymeric pipe material is heated to be rendered plastic and biaxially deformable before being conveyed through the system, via the tie bar. Wherein the tie bar contains a plurality of channels for transporting fluid to different portions of the system. The first channel injects fluid over the mandrel, with the mandrel receiving a heated fluid that flows over the mandrel's surface counter-current to the pipe material, to lubricate the mandrel and increase friction between the pipe and the mandrel. The second channel collects the fluid from the mandrel to be reheated and recirculated.