# 1988 Bath
The development of a new generation of polyethy lene pipe materials for elevated temperatures has been going on at Neste Polyeten for more than 10 years. A new MDPE grade can be used up to 47 °C at a design stress of 5,0 MPa and a life-time of 50 years. A further development Will increase the temperature to 55 60 "Cc, Im portant knowledge about polymers, additives and failure mechanisms have been reached. Also the chemical resistance have been studied, and good results have been obtained. A better definition of the fcR-factor is suggested. The new grade has successfully been used in many applications.
For pressure pipe systems thermoplastic FE pipe materials are designed for a working temperature up to 20 °C without any restrictions. Crosslinked PE (XLPE) is often uncompetitive at temperatures below 50 °C, owing to high price on both pipes and fittings. In the temperature range of 20 - 50 *C the normal procedure is to use reduction factors on thermoplastic PE, i e increase wall thickness, reduce pressure etc. 10 years ago Neste Polyeten AB (formerly Unifos Kemi AB) started a project aimed to find a thermoplastic MDPE to be used at. temperatures up to 50 60 °C without the need of using these reduction factors.