What is it about?
We investigated the existing standards for plane strain fracture toughness testing on polyethylene resins used in the production of extruded water pipes. The work was necessary, because the existing standards do not agree between themselves in what is the correct procedure for the test. In particular, pre-cracking is a critical issue in this kind mechanical test and the prescribed procedure was conflicting among standards of the same standard association (in this case ASTM). In order to produce valid results for KIc, the resin was tested at liquid nitrogen temperature.
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Why is it important?
Polyethylene pipes are being used in most water distribution systems worldwide. The use of a plastic resin has many advantages, but an important shortcoming is that these resins suffer creep in service and may fail by localized fracturing, which causes water leakage (with both economic and environmental deleterious impact). Understanding the resistance to crack propagation is needed, therefore, to produce more reliable water distribution systems.
Perspectives
This was the first work published by Dr. Moreno Perez in his PhD at the Escola Politecnica da USP. At the time he started his work, he was employed by SABESP as materials engineer. During his PhD he left the company and now he is professor at the Universidade Tecnologica Federal do Parana (UTFPR) in Londrina-PR, Brazil. It was a pleasure to have him in my research group.
Professor Claudio Geraldo Schön
Universidade de Sao Paulo Campus da Capital
Read the Original
This page is a summary of: Effect of precracking method on KIc results for medium-density polyethylene tested under cryogenic condition, Polymer Testing, September 2010, Elsevier,
DOI: 10.1016/j.polymertesting.2010.05.006.
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