Study of cupper ion and pressurization effect on durability of polyethylene for hot water supply

Abstract

The effect of cupper ion and pressurization on oxidation degradation of polyethylene was studied by hot water immersion test. Non-cross-linked PE-RT test specimen was used. By compressing air at 0.4 and 0.7MPa in an autoclave, the test specimens were immersed at 98°C in hot water for 7,000h. In cupper ion aqueous solution of 3,000ppm, the immersion test was also conducted in addition to compressed air. The results of test specimen under normal condition at 0.1MPa at 98°C in hot pure water were compared.

The compressed air and cupper ion made the anti-oxidation ability almost zero until immersion time of 3,500h and the oxidation layer was generated at the surface of test specimen after 5,000h. The auto-oxidation reaction was assumed to be promoted from the results of ESR analysis. Cupper was also involved remarkably in the test specimen at 50μm depth or more from the surface by ICP-MS analysis. The intruded cupper was possible to accelerate radical formation catalytically.