Journal of Materials Life Society
Online ISSN : 2185-7016
Print ISSN : 1346-0633
ISSN-L : 1346-0633
Volume 27 , Issue 3
Showing 1-3 articles out of 3 articles from the selected issue
Original Papers
  • Kazuhisa IGAWA, Hidekazu HONMA, Sakiko FUKUNISHI, Kazushi YAMADA, Hiro ...
    2015 Volume 27 Issue 3 Pages 63-69
    Published: October 31, 2015
    Released: June 04, 2019

    The hydrostatic stress rupture test has conventionally been conducted as a useful method of lifetime evaluation. The hot water circulation test which is reflected to the actual operating condition is also useful method. The correlations and differences between the two tests were examined. Compared with the hydrostatic stress rupture test, it was found that the antioxidant in the resin was eluded into the circulating water and was consumed rapidly in the hot water circulation test. The lifetime of the pipe became shorter in the hot water circulation test. In addition, it was also found that when using the brass fittings, copper ions eluded from the joint accelerated degradation of a resin, a crack initiation at the pipe inner surface and a slow crack growth through the pipe thickness due to the hoop stress.

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  • Kazuhisa IGAWA, Hidekazu HONMA, Kazushi YAMADA, Hiroyuki NISHIMURA
    2015 Volume 27 Issue 3 Pages 70-76
    Published: October 31, 2015
    Released: June 04, 2019

    This paper describes comparison of test results between the conventional hydrostatic stress rupture test and various accelerated durability tests considering the actual using condition using polyethylene pipes for heating and hot water supply containing a relative small amount of antioxidants which have low mobility in a resin. It was found that the dissolved oxygen in hot water and the diffusion factor of oxygen in a resin affect the degradation of a pipe. It was also clarified to the temperature dependence of oxidative degradation by the hot water circulation test and copper ion aqueous solution circulation test and to the mechanism of generation of thermal degradation by copper.

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