Structures in Sulfur-crosslinked EPDM Analyzed by Hahn Echo Method
Hitoshi IWABUKI , Kazuya NAGATA , Toru NOGUCHI and Eisuke YAMADA![](images/78-7-1-3.gif)
Industrial Technology Center of Okayama Prefecture, Okayama, Japan
Nissin Kogyo Co., Ltd., Nagano, Japan
Aichi Institute of Technology, Toyota, Japan
Nippon Gomu Kyokaishi,(2005),78(7),255-259 Original Paper in Japanese
Abstract
Sulfur-crosslinked EPDMs were examined by H pulsed NMR. Spin-spin relaxation time (T2) was measured by Hahn echo method. The decay curve was resolved into two components, T2n and T2nn, which were arising from network molecules and non-network molecules, respectively. For unfilled EPDMs prepared at varying sulfur content, the higher order structures analyzed by Hahn echo method were almost the same as those analyzed for peroxide-crosslinked EPDMs. The reciprocal of T2n measured at 150 for unfilled EPDMs increased linearly with increase in apparent crosslinking density ( S) values determined by modified Flory-Rehner equation. For EPDMs filled with carbon black (CB), the crosslinking density of rubber phase ( R) was calculated from the relationship between S and 1/T2n for unfilled EPDMs.The crosslinking density related to CB ( F) was obtained from the difference between the S and R. The F values showed good correlation with the tensile stress at 100% elongation, independent of the kinds of cure agents.
(Received on February 2, 2005)
(Accepted on May 6, 2005)
Keywords:
EPDM, Crosslinking density, Pulsed NMR, Hahn echo method, Spin-spin relaxation time |