H-1-NMR imaging study of molecular mobility in carbon black-filled, TBBS-sulfur-vulcanized cis-polyisoprene

摘要

The distributions of the T-2 relaxation times in carbon black filled, TBBS-Sulfur vulcanized cis-polyisoprene were were studied using H-1 NMRI spin-echo experiments. It has been reported that more than two T-2 relaxation times are observed in carbon black-filled rubbers, reflecting the existence of tl-le hard regions adjacent to the crosslinks or filler particle and soft regions distant from such rigid components. Our current concern is how the amount and distribution of the T-2 times are affected by the filler incorporation in the rubber compounds. A decrease in the T-2 relaxation times with an increasae in carbon black content is observed. The average T-2 time, [T-2], drops from 11.38 ms with no carbon black to 10.05 ms with 15 phr carbon black. The [T-2] further decreases when the black loading level is increased form 15 to 30 phr and 30 to 50 phr, but the magnitude of the changes in the [T-2]s are not as large as in the initial loading (0 to 15 phr). The observations of the [T-2]s suggest inhomogeneities are induced in the network structure by the black incorporation. The distribution of the T-2 relaxation times becomes narrower as the black loading level increases. There are at least four factors governing the intensity of the images in the swollen, filled rubber vulcanizates as well as the NMR parameters (T-1, T-2, T-R, and T-E: (1) H-1 spin density, (2) inhomogeneity of the network structure, (3) degree of swelling in the sampling solvent, and (4) displacement effect of the carbon black. (C) 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1385-1390, 1998. [References: 16]