![]() ![]() ![]() Most PEX standards include some sort of notched pipe test to demonstrate adequate resistance to crack propagation when a defect (notch) is present. In general, the three common methods of crosslinking, peroxide, silane grafted, and radiation, are treated equally in the standards with regard to physical and mechanical properties. PEX materials are generally believed to have very good slow crack growth properties and some would argue that they are immune to slow crack growth. This study reports PENT data for PEX pipe resins, which allows a more direct comparison of the slow crack growth properties of crosslinked PE pipe grades with standard PE pipe grades.Ĭrosslinked Polyethylene (PEX) pipe and tube are being used globally for potable water plumbing systems, industrial piping systems, radiant heating systems, etc., successfully. Unfortunately the methods used to measure the slow crack growth resistance of PEX are different than those used for standard polyethylene (PE) pipe grades. Crosslinked polyethylene (PEX) is known to have very high slow crack growth resistance as a result of crosslinking. ![]() Failure time has increased from a few hundred hours to over 50,000 hours in some cases. Results are reported as hours to failure. The most common test method for pipe products is ASTM F1473, Standard test Method for Notch Tensile Test to measure the resistance to Slow Crack Growth of Polyethylene Pipes and Resins (PENT). The performance of HDPE resins with regards to slow crack growth has increased dramatically over the past two decades. ![]()
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