The development of a new family of PE materials with significantly improved processability andlong-term strength at high temperatures is discussed. These polymers form the basis for a newISO class of polyethylene materials: PE-RT (Polyethylene of Raised Temperature resistance) forhot and cold water as well as industrial pipe applications. These materials have a uniquemolecular structure and crystalline microstructure, which provides excellent Long TermHydrostatic Strength at high temperatures without the need for cross-linking the material.