Medienbeständigkeit von Polyethylen für Langzeitanwendungen

Translated title of the contribution: Chemical resistance of Polyethylene for long-term applications

Sylvana Wetscher

Research output: ThesisMaster's Thesis

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Abstract

Due to their wide range of applications pipes and geomembranes made of Polyethylene (PE) are exposed to various aggressive media during their whole lifetime. For the investigation of the chemical resistance of the materials, time-consuming exposure tests are carried out since decades. To be able to characterize the influence of different media on the long-term behavior of PE materials within feasible testing times, new accelerated methods are required. Based on this statement different PE pipe grades for high temperature applications and different PE geomembrane grades were investigated by means of conventional exposure tests with respect to the influence of different media on the aging behavior and the mechanical properties. Therefore an extensive exposure program was scheduled and characterizations on compression molded plates were carried out. Furthermore a special test cell was developed and implemented in order to analyze possible changes of the crack resistance of the geomembrane materials via cyclic fracture mechanical tests on cracked round bar (CRB) specimen in the medium. Therefore, two different media and seven different exposure times were chosen. Furthermore the pipe grades were exposed at two different temperatures, while the geomembrane grades were only exposed at one temperature. Supsequently standardized re-drying was done and the aging behavior was characterized by infrared spectroscopy, as well as by differential scanning calorimetry (DSC) in order to detect the oxidation induction time (OIT) and the degree of crystallinity. Additionally the mechanical properties were dertermined through tensile tests. Basically the exposure did not cause any aging of the materials. This was proven by the results of the DSC, where the crystallinity was not influenced and the OIT decreased, but still was measurable after 90 days. Additionally the infrared spectroscopy revealed that carbonyl-groups had formed in the material due to the re-drying. Furthermore a softening effect of the media on the stiffness and the crack resistance of the materials was observed by a decrease of the elastic modulus and a shift of the failure curve of the cyclic CRB-tests towards higher cycle numbers. An influence of the exposure temperature, as well as differences between the influences of the media could not be detected by means of these test methods.
Translated title of the contributionChemical resistance of Polyethylene for long-term applications
Original languageGerman
QualificationDipl.-Ing.
Supervisors/Advisors
  • Redhead, Anita, Supervisor (internal)
  • Pinter, Gerald Gerhard, Co-Supervisor (internal)
Award date1 Jul 2011
Publication statusPublished - 2011

Bibliographical note

embargoed until 03-06-2016

Keywords

  • Polyethylene
  • pipes
  • geomembrane
  • impact of environments
  • long-term applications

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