|The Degradation Mechanism of NBR Invaded by High Concentration Chlorine Water
Panwashlet CO.,LTD, Material Research Sec.,Kitakyushu, Japan *1
Chemicals Evaluation and Research Institute, Japan, Saitama, Japan *2
Department of Materials Science, Graduate School of Science and Technology, Nagasaki University, Nagasaki, Japan *3
Nippon Gomu Kyokaishi,(2005),78(3),98-102 Original Paper in Japanese
In order to elucidate the degradation behavior of NBR caused by high concentration chlorine water, NBR samples corroded in 200 ppm chlorine water and in pure water were analyzed by means of EPMA, FT-IR and XPS.
The degradation process of the NBR corroded in high concentration chlorine water is considered as follows: (1) an ƒ¿-H of the butadiene double bond in NBR molecule is subject to substitution by chlorine; (2) the chlorinated NBR abstracts an ƒ¿-H in another NBR molecule to cause the elimination of HCl, which generates polymer radicals; (3) the polymer radicals thus produced add to polybutadiene double-bonds in the other NBR. It is concluded that residual chlorine reacts with NBR by chlorination and oxidation mechanisms and that these reactions lead to hardening and degradation of NBR through the increase in the crosslinking density.
(Received on October 18, 2004)
(Accepted on January 26, 2005)
NBR, Degradation mechanism, Hardening, High concentration chlorine water, EPMA, FT-IR, XPS