Xe-129 nuclear magnetic resonance investigation of carbon black aggregate morphology

The morphology of three 'normal' ASTM carbon black reinforcement fillers (N 110, N347, and N472) is investigated for the first time using one- and two- dimensional Xe-129 nuclear magnetic resonance (NMR) spectroscopy. A wide ra nge in Xe-129 NMR chemical shift is observed among samples, and is attribut ed to variations in the physical nature of the unoccupied volume formed by the subunit particles of the aggregate. 129Xe NMR chemical shift and integr ated intensity parameters are extracted from a single one-dimensional exper iment, and interpreted in terms of aggregate void size, volume, and density . The rate of exchange of Xe-129 atoms between different aggregates in a th ree component blend is approximated using two-dimensional exchange NMR spec troscopy, and found to occur on a timescale similar to 6 ms less than or eq ual to tau(ex)less than or equal to similar to 100 ms. No evidence of xenon exchange between samples N110 and N472 was observed on timescales less tha n 100 ms, an apparent consequence of the small aggregate void size in these samples. The 129Xe NMR chemical shift assignments for samples N110, N347, and N472 are shown to be not significantly shifted from their non-exchangin g values. (C) 1999 Elsevier Science Ltd. All rights reserved.