|Recent Studies on Crosslinked
Rubbers by Pulsed NMR
Nissin Kogyo Co., Ltd Nagano,Japan.
Industrial Technology Center of Okayama Prefecture Okayama,Japan.
Nippon Gomu Kyokaishi,(2003),76(5), 178-184 General Review in Japanese.
Pulsed NMR, which is used for measuring spin-spin relaxation time, T2, and spin-lattice relaxation time, T1, has a unique advantage over other techniques because it can provide direct information on molecular motion and volume fraction of each component in the composites.
Rubber-Carbon black interactions are very important to study the reinforcement of rubbers. The T2 signal of the bound rubber was resolved into two components, short T2 component and long T2 component. In a two-phase model for interpreting the reinforcement, one phase was the immobilized rubber layer around carbon blacks, and the other was the rubber away from the filler surface.
On the other hand, Folland and co-workerssuggested that unfilled isoprene rubber crosslinked by irradiation consisted of two components such as network structures and non-network structures.
Recently, Noguchi and co-workers reported the results from a pulsed NMR spectroscopy
with Hahn echo method for EPDM specimens and their relations with the dynamic fatigue behaviors. The retention of stress under fatigue for peroxide-crosslinked EPDM filled with carbon black, calcium-carbonate, or silica, tended to decrease as the network T2 became longer and the non-network fraction became larger.
This result suggests the relationships between the fatigue behavior and the non-network fraction as well as the molecular mobility of the network component.
Pulsed NMR, Solid scho method, Hahn echo method, Higher order structure,
Bound rubber, Network component, Non-network component, Filler, Fatigue