Part VIII: N.M.R. Absorption by Water in Wool During Changes of Water Content

Abstract

The change with time of the nuclear magnetic resonance absorption by water in wool was observed during uptake and loss of water following relative humidity changes between near zero and 70%, 80%, and 93%. Exchange of D₂O by H₂O was also observed at 93% RH. During both uptake and loss of water the results indicate that line broadening is taking place because of reduced mobility of some protons. It is suggested that this low mobility follows, at least in part, from a low level of H-bond network formation during the transient state. In desorption most of the more mobile water is quickly removed and thereafter its concentration is small. The constant- regain diffusion coefficient for water in wool at 21° C and 93% RH calculated from the D₂O-H₂O exchange experiment was approximately 1.5 X 10^-8 cm²/sec. It appears that the corresponding intrinsic diffusion coefficient lies between conflicting values found by other workers. The exchange curve, which should be a good approximation to a self-diffusion curve, deviated grossly from a Fickian shape after the first minute. It was found that the n.m.r. signal depended on previous sorption history if the wool was not thoroughly wetted-out before a test.