|Inhomogeneous Structure in Natural Rubber Vulcanizate under Deformation
Industrial Technology Center of Okayama Prefecture, 5301 Haga, Okayama, Japan
Nissin Kogyo Co., Ltd., 801 Kazawa, Toumi-shi, Nagano, Japan
Aichi Institute of Technology, 1247 Yachigusa, Yakusa-cho, Toyota, Japan
Nippon Gomu Kyokaishi,(2007),80(3),83-85 Original Paper in Japanese
Inhomogeneous structure in natural rubber (NR) vulcanizate was examined by 1H pulsed NMR. The spin-spin relaxation times (T2) under various extension ratios (ƒ¿) were measured by the Hahn echo method and the solid echo method. The decay curves of NRs were resolved into three T2 components, T2SS, T2HS, and T2HL, which were respectively arising from the strain-induced crystalline chains, the network chains, and the more mobile chains that were less affected by crosslinks or entanglements. T2HS and T2HL decreased with increasing ƒ¿. However, T2HL leveled off at ƒ¿ beyond 4 while T2HS kept decrease. The decrease in T2HL with ƒ¿ was more rapid than that of T2HS until T2HL became constant. This indicates that the deformation of the more mobile chains was larger than that of the network chains. The increase in the fraction of T2SS component with increasing ƒ¿ was observed in the region of ƒ¿ that T2HL were almost unchanged. It was suggested that the strain-induced crystallization is closely related with the more mobile chains.
(Received on June 7, 2006)
(Accepted on December 30, 2006)