Chemical degradation of pipe grade polyethylene in the chlorinated water-Effect of comonomer type and distribution

In this research, the effect of the distribution and type of comonomer of pipe grade polyethylene on the chemical resistance against chlorine dioxide as a drinking water disinfectant is investigated. The type and distribution of comonomer leads to the difference in the crystalline microstructure and eventually the difference in resistance of the grades against chlorinated environment. Two grades of PE80 (AK-80 with 1-butene comonomer and AS-80 with 1-hexene comonomer) were aged in a water solution containing 10 ppm of chlorine dioxide. The rate of loss of elongation at break  in AK-80 and AS-80 in the fifth week of aging was 95% and 33%, respectively, and it shows the stability of AS-80 compared to AK-80. The low amount of comonomer in AS-80 leads to the reduction of weak points in polymer chain prone to chemical degradation. Longer length of the comonomer in AS-80 increases the entanglement between the chains and, as a result, makes this sample more suitable when exposed to a chlorinated media.