EXPERIMENTAL STUDIES OF HIGH DENSITY POLYETHYLENE EXPOSED TO CHLORINE DIOXIDE MEDIA WITH VARIOUS CONCENTRATIONS AND TEMPERATURES

High density polyethylene (HDPE) is one of the most widely used materials in the pipe industry because of its several advantages such as low price, excellent productivity, light weight and high resistance to chemical degradation. For potable water pipes, their lifespans are supposed to be over 50 years, so it is essential to check their long-term performance in certain service conditions. The point is that potable water contains disinfectants including chlorine or chlorine dioxide which shortens the service time of water pipes. In addition to disinfectant, environmental conditions like internal pressure and temperature of media inside also cause deterioration of properties of plastic pipes. To understand the degradation mechanism by potable water, we focused on two parameters, the concentration of disinfectant and the temperature of the solution. In this study, specimens obtained from HDPE pipes were artificially degraded in 5 different kinds of chlorine dioxide solutions with various concentrations and temperatures. Micro-tensile tests were conducted to study the variation of mechanical properties of HDPE specimens. The fourier transform infrared (FTIR) spectrometry and the gel permeation chromatography (GPC) analysis were also conducted to study the variation of chemical properties of HDPE according to exposure time to chlorine dioxide solutions.