Plastic Pipes Conference Association # 2010 Vancouver
S.Joseph
Companies of LyondellBasell FNCT (Full Notched Creep Test, ISO DIS 16770-3) and PENT (Pennsylvania Notch 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 multimodal polyethylene resins has resulted in a step-change increase in FNCT and PENT failure times. End-use applications have also begun to incorporate requirements that represent a higher level of performance. For instance, in Europe the DVGW requirement for sandless bedding of water pipes requires FNCT > 2700 hours, and proposed regulations for PE pipe in nuclear plant secondary cooling-water applications in North America require 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 provide 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 high-performance polyethylene pipe resins.
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