Degradation of unstabilized medium‐density polyethylene pipes in hot‐water applications
- 1 September 1994
- journal article
- research article
- Published by Wiley in Polymer Engineering & Science
- Vol. 34 (17), 1354-1361
- https://doi.org/10.1002/pen.760341708
Abstract
Pipes of an unstabilized medium-density polyethylene have been pressure tested with internal stagnant water and moderately circulating air as the external medium at temperatures ranging from 70 to 105°C and changes in molecular structure and crystallinity have been studied. The stage III (fracture induced by thermal oxidation) life of the unstabilized polyethylene pipes was less than 12% of the life of the corresponding stabilized polyethylene pipes. Infrared spectroscopy and size exclusion chromatography showed an earlier and more extensive increase in the quantities of oxidation end-products and a more pronounced decrease in molar mass of the outer-wall-material than of the inner-wall-material of the pipe. Mass crystallinity, measured by differential scanning calorimetry, increased on an average by a quantity corresponding to 45 methylene groups per chain scission event. The life of the unstabilized pipe was divided into an induction period during which no detectable thermal oxidation occurred and a subsequent polymer degradation period. The induction period exhibited an Arrhenius-temperature-dependence with an activation energy of 75 kJ mol−1.Keywords
This publication has 13 references indexed in Scilit:
- Heat capacities of linear high polymersPublished by Springer Science and Business Media LLC ,2006
- Molecular structure, morphology, and antioxidant‐ consumption in polybutene‐1 pipes in hot‐water applicationsPolymer Engineering & Science, 1993
- Modeling of antioxidant loss from polyolefins in hot‐water applications. I: Model and application to medium density polyethylene pipesPolymer Engineering & Science, 1992
- Molecular structure, morphology, and antioxidant consumption in medium density polyethylene pipes in hot‐water applicationsPolymer Engineering & Science, 1992
- Molecular structure and morphology of crosslinked polyethylene in an aged hot‐water pipePolymer Engineering & Science, 1990
- The thermo-oxidative degradation of polyolefines—Part 10. Correlation between the formation of carboxyl groups and scission in the oxidation of polyethylene in the melt phasePolymer Degradation and Stability, 1980
- Differentialthermoanalyse von PolyäthylenJournal of Thermal Analysis and Calorimetry, 1974
- Polymer crystallinity determinations by DSCThermochimica Acta, 1970
- Infrared study of oxygenated groups formed in polyethylene during oxidationJournal of Polymer Science, 1960
- Infrared spectrophotometric studies on polyethylene. II. OxidationJournal of Polymer Science, 1954