Thin samples of a pipe-grade polyethylene with a bimodal molecular weight distribution were exposed to 5 ppm chlorinated water at 70 °C for up to 3000 hours. The samples were characterized by tensile tests, size-exclusion chromatography, infrared spectroscopy, and differential scanning calorimetry. Throughout exposure, the molecular weight data showed evidence of degradation: weight-average molecular weight was reduced, and a shift occurred in the molecular weight distribution from a bimodal to a unimodal distribution (decreased dispersity). After 2250 hours of exposure, brittle behavior was observed, in which the average elongation at break was 12%. At this level of degradation, the weight-average molecular weight was 9% of its undegraded value, and the crystallinity had increased from 70% to 85%. Average tensile strength was reduced from 31.8 to 16.6 MPa. The data imply that the presence of short-chain branching may inhibit chemicrystallization and subsequently delay the onset of brittle behavior.
|Original language||English (US)|
|Title of host publication||SPE ANTEC 2020|
|Subtitle of host publication||The Annual Technical Conference for Plastic Professionals|
|Publisher||Society of Plastics Engineers|
|Number of pages||6|
|State||Published - 2020|
|Event||SPE ANTEC 2020: Annual Technical Conference for Plastic Professionals - Virtual, Online|
Duration: Mar 30 2020 → May 5 2020
|Name||Annual Technical Conference - ANTEC, Conference Proceedings|
|Conference||SPE ANTEC 2020: Annual Technical Conference for Plastic Professionals|
|Period||3/30/20 → 5/5/20|
Bibliographical noteFunding Information:
The authors gratefully acknowledge the financial support under Grant NSF/CMMI-1462080 to the University of Minnesota from the U.S. National Science Foundation. Parts of this work were carried out in the Characterization Facility at the University of Minnesota, which receives partial support from the National Science Foundation through the MRSEC program.
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