DETERMINATION OF THE DEGREE OF CELLULOSE CRYSTALLINITY IN WOOD BY C-13 NUCLEAR-MAGNETIC-RESONANCE SPECTROSCOPY

A new method for determining the degree of cellulose crystallinity exploits differences in proton rotating-frame relaxation time constants for cellulosic and non-cellulosic domains within samples of wood. Combinations of 11C NMR spectra run with spin-locking pulses of different durations provide a spectrum of the cellulose, free of interference from other NMR signals. The relative areas of bands assigned to C-4 arc then used to determine crystallinity, as in earlier studies of pure cellulose. A survey of woods from species taken at random gave mean cellulose crystallinities of 0,54 for 6 hardwoods and 0,57 for 5 softwoods, with standard deviations of 0,02 and 0,03 respectively. © 1990, Walter de Gruyter. All rights reserved.