STRUCTURAL AND FRACTURE METHODS AS MEANS OF PREDICTING THE LIFETIME OF HDPE PIPES

摘要

High-density polyethylene (HDPE) is being used more and more in critical long-term application, such as in pipes for the distribution of water and gas. For this reason it is important to have a strong understanding of those parameters which control the fracture behaviour of HDPE. The main parameters are (ⅰ) chain structure, (ⅱ) morphology and (ⅲ) processing conditions. The structure is characterised by SIS/DSC method (SIS-Stepwise Isothermal Segregation), DSC and "rapid" SIS/DSC. For evaluation the failure mode (long term brittle failure), which limits the lifetime of HDPE pipes accelerated PENT (Pennsylvania Notch Test) and FNCT (Full Notch Creep Test) tests have been applied. A correlation between fracture and structure parameters has been found.