Plastic Pipes Conference Association # 2012 Barcelona
Nishimura Hiroyuki
The effect of antioxidants of polyethylene of raised temperature resistance (PE-RT) pipes for a long lifetime for hot water supply and for space heating was evaluated in this paper. Some polyethylene specimens mixed with different amount of antioxidants such as hindered phenol and hindered amine were prepared by injection molding. The specimens were immersed in hot water and exposed to hot air at the temperature of 60, 80, 98(100), and 120 °C for 10000 hours or more. After that, the tensile test and the thermal analysis were carried out. The tensile strength of specimens immersed and exposed at 98 and 120 °C was higher than that of the blank specimens because the crystallization of specimens has progressed. There was a great variability among the elongation at breakage. As a result of the thermal analysis, it was found that resin degradation was not advance for 5000 hours because there was no change in the melting point. As a result of the Oxidation Induction Time (OIT) measurements, it was found that antioxidants were remained in a resin. From the longterm degradation test of PE-RT mixed with different amount of antioxidants, it was found that the original resin of PE-RT degraded for 7000 hours or more because there was almost no antioxidant.
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