# 2006 Washington DC
The development of a new family of PE materials with significantly improved processability and long-term strength at high temperatures is discussed. These polymers form the basis for a new ISO class of polyethylene materials : PE-RT (Polyethylene of Raised Temperature resistance) for hot and cold water as well as industrial pipe applications. These materials have a unique molecular structure and crystalline microstructure, which provides excellent Long Term Hydrostatic Strength at high temperatures without the need for cross-linking the material. PE-RT type materials have been used successfully in domestic hot and cold water piping systems for more than 20 years, and in application areas such as underfloor heating and radiator connections. More recently, the easy processing and outstanding material properties have also made these resins attractive for use in many larger diameter industrial applications, where regular Polyethylene cannot be used due to its high temperature limitations. In this respect PE-RT can also compete with high-end engineering plastics, offering significant cost savings. The use of PERT materials provides significant process advantages to the converters, allowing high line speed pipe production and providing excellent flexibility and ease of installation for the application. A recently developed PE-RT type material still offers higher long-term strength at high temperature and further improved processability, for example in larger diameter cooling water pipes in power plants. Pipes based on these materials can be connected via heat fusion welding or by the use of mechanical fittings. Furthermore, this material can be used in industrial applications, where its temperature resistance may limit traditional Polyethylene and metallic materials often suffer from corrosion. The excellent weldability of these materials provides various opportunities to connect even larger dimension pipes in industrial applications, an example of this being the use in multi-layer structured oil pipelines onshore and offshore. This paper presents the material science and product design concepts that govern the high longterm hydrostatic strength at high temperatures. By controlling the molecular structure, the melt rheology and solid-state properties can be influenced, which results in a unique balance of processability and hydrostatic strength. Also discussed are the product features and benefits of PE-RT materials. The paper shows examples of the application range for this type of product, using applications in the domestic pipes market as a reference.