Plastic Pipes Conference Association # 2010 Vancouver
Resistance to slow crack growth is an important material property of polyethylene which determines the application lifetime, especially for utility pipe applications. Usually, the slow crack growth resistance of materials is assed by time consuming testing methods such as NPT, FNCT, PENT, etc. These methods require often the use of notched samples, the use of specific fluids (e.g. detergents) and elevated temperatures. In this paper, we present an elegant method to predict slow crack growth resistance in materials in a simple, very accurate and fast way. The resistance to slow crack growth is predicted from a simple tensile measurement at a temperature of 80 C. It will be shown that the slope of the stress-strain curve above its natural draw ratio (i.e. strain hardening) correlates very well with the results obtained by the full notch creep test (FNCT) of the same materials. The strain hardening method is an elegant method which does not require notched specimen and/or detergents. Besides the advantage that the method is easy to implement in laboratories, its main advantage is the dramatic decrease of measurement times from thousands of hours to only a few. This method is very suitable in the development of new grades by researchers, but also very valuable as batch release test for both resin suppliers and pipe converters.
Author(s) : Rieky Steenbakkers, Linda Havermans, Patrick Voets, Jonathan Rabiei, Rudy Deblieck
The resistance to Slow Crack Growth of HDPE is related to the strain hardening modulus as determined from a tensile test at 80 °C. Correlatio ns between traditional methods (e.g. Full Notched Creep Test, Notched Pipe Test) and other accelerated tests (e.g. fatigue testing) show that the same failure mechanism is...
Author(s) : Havermans Linda
Resistance to slow crack growth is an important material property of polyethylene which determines the application lifetime, especially for utility pipe applications. Usually, the slow crack growth resistance of materials is accessed by time consuming testing methods such as NPT, FNCT, PENT, etc. These methods require...