Polyethylene used in Industrial Applications at Eleveated Temperatures

Applications at elevated temperatures like cable conduit pipes for high voltage cables, pipelines used in oil industry or in industrial plants offer new possibilities for PE but additional requirements in such applications have to be taken into account. Long term experience in using PE100 pipes with respect to easy and quick installation as well as reliable operation let pipe producers raise the question, if for these new or modified applications, completely new pipe materials are required or if PE100 materials with adjusted properties can meet the requirements. This paper presents examples for new applications and their specific solutions using modified PE100 resins and provides insights into the additional requirements and material science. INTRODUCTION Over the last 60 years, plastic pipes made from High Density Polyethylene have been successfully used in exterior applications like gas and water supply as well as in interiors application for heating, plumbing and gas supply. For some applications, an extended temperature range beyond the typical limit of max. 40 °C for regular HDPE pressure pipe resins is required. In the above mentioned interior pipe applications, PERT materials are well established as they easily last for 50 years at much higher temperatures. A very important difference between PE100 and PERT resins is the difference in long term heat resistance [1]. For Example the typical pressure testing according to ISO 9080 of a PE100 resin allows an extrapolation to 50 or even 100 years at 20 °C while at 60 °C the extrapolation can only guarantee a lifetime of about 5 years. In contrast to that a PERT Type II resin tested according to ISO 24033 will last for 100 years at this temperature. There are several industrial applications were the temperature profile of PERT materials together with PE100 properties provide an ideal combination of properties e.g. in cable conduit pipes for high voltage cables, pipelines used in oil industry for waste water or riser systems or in industrial plants for hot liquids. But in such applications further requirements exist which exceed standard PERT pipe requirements including UV and chemical resistance as well as limits for permeation.