Comparison of FNCT vs. PENT as commonly used test methods for ESCR performance of HDPE

Session 11A
4:30 pm

Sebastian Joseph, Equistar Chemicals, LP

FNCT (Full Notched Creep Test, ISO DIS 16770-3) and PENT (Pennsylvania Edge-Notched Tensile Test, ASTM F-1473) are commonly used test methods to measure the stress-crack resistance of polyethylene resins used in pressure pipe applications. FNCT test is primarily used in Europe whereas the PENT test is used in North America. The advent of high-performing bimodal and multi-modal polyethylene resins has resulted in a step-change in failure times from FNCT and PENT. End-use applications have also begun to reflect the higher-performance. For instance, in Europe DVGW requirement for sandless bedding of water pipes requires FNCT > 2700 hours and PE pipe in cooling-water applications in North America requires PENT > 2000 hours. Accelerated versions of the FNCT test have been developed to reduce failure times by an order of magnitude. An increase in stress and or temperature in the PENT test provides a smaller degree of acceleration. An investigation into the potential correlation of PENT failure times with accelerated FNCT test failure times is conducted in this paper, in order to determine whether the FNCT test can be used as a QC tool for release of high-performance polyethylene pipe resins.

Sebastian Joseph, Product & Application Development, North America
Heinz Vogt, Product & Application Development, Europe
Hans-Friedrich Enderle, Polymer Physics & Characterization, Europe
Everett Lewis, Manufacturing, North America

LyondellBasell Industries