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Alternative Fast Methods to Evaluate the Long-Term Performance in Polyethylene Resins with High Resistance to Crack

 

Papers # 2014 Chicago

Slow Crack Growth (SCG) is the most critical failure mechanism in high density polyethylene used in pipe applications to determine the long-term performance of the resin. The most common methods for evaluating the SCG resistance are the Pennsylvania Edge Notched Tensile (PENT), Full Notch Creep Test (FNCT) and the Notched Pipe Test (NPT). In this paper a modified PENT test with higher load and temperature conditions (2.8 MPa and 90ºC) has been introduced. This approach provides a failure time reduction around six times, but guaranteeing a SCG process. On the other hand, the strain hardening (SH) modulus determination through the tensile test is confirmed as a very good method to correlate with PENT (standard and also modified) and FNCT test. In this work, different geometries and test conditions to determine the SH modulus have been evaluated in order to find the best correlation with conventional tests. Both, modified PENT test and SH method seem to be very good alternatives to evaluate the failure resistance of the new high resistance polyethylene pipe grades.

Related keywords : test, strain, standard, resistance, modules, process.
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