A. Redhead, A. Frank, G. Pinter
Papers # 2012 Barcelona
Keywords : polyethylene for raised temperature resistance, chlorine dioxide, oxidative resistance, degradation, embrittlement Two different polyethylene pipe grades for raised temperature resistance (PE-RT) and one PE100 grade were investigated concerning their resistance to chlorine dioxide. Conventional test methods like immersion tests with subsequent tensile tests, Oxidation Induction Time (OIT) and Infrared (IR)-spectroscopy where chosen to observe potential physical and chemical aging of the materials. Additionally cyclic tests with cracked round bar (CRB) specimens were conducted for the determination of the impact on the longterm failure behavior. These tests were carried out at a temperature of 23 °C under two different configurations : tests in air on unexposed and exposed specimens and tests in chlorine dioxide inside a special glass cell. For immersion tests with thin films and the CRB specimens, exposure temperatures of 23, 30 and 40 °C where chosen for a predefined exposure time. Meanwhile, the concentration of the chlorine dioxide was supervised via Ultraviolet/Visible light (UV/VIS)-spectroscopy. Based on the generated results a change in the mechanical properties was found, emphasizing the effect of chlorine dioxide on the physical and chemical aging of the materials, where an increase of the impact at elevated exposure temperature and increasing time was established. A thermo-oxidation due to exposure was revealed via OIT and IR-spectroscopy. However, the material ranking via cyclic CRB tests did not show any effect of chlorine dioxide on the crack initiation time, the time of slow crack growth and the total failure time.