FUNDAMENTAL STUDIES ON THE INTERACTION BETWEEN MOISTURE AND TEXTILES

PART II. PULSED PROTON BROADLINE NMR STUDY ON THE MOISTURE SORPTION OF CELLULOSIC FIBERS

Abstract

The interaction between moisture and cellulose was investigated by pulsed proton broadline NMR spectroscopy. Five kinds of cellulosic fibers; such as scoured ramie, scoured cotton, mercerized cotton, normal viscose rayon, and high-tenacity rayon, were used as test specimens differing in the degree of crystallinity as widely as possible. The specimens were conditioned at various relative humidities from dryness up to saturation at 30°C. The investigation was performed by resolving the proton free induction decay signal into three different j's relaxation processes with fractional initial intensities, A_j, and spin-spin relaxation times, T_{2, j}: i.e., a fast decay process shown as A_s and T_{2, s}, and two slow decay processes shown as A_m and T_{2, m} and A_l and T_{2, l}.
The relaxation times, T_{2, s}, T_{2, m}, and T_{2, l}, were found to be in the orders of several μsec, several hundred μsec, and several msec, respectively, according to the amount of moisture sorbed in the specimens. The results enabled us to assign the relaxation processes to the motion of protons of cellulose and tightly bound water, of bound water, and of loosely bound water, respectively.
Subtracting the water proton contents determined from the values of A_m and A_l, from total water proton content determined from the moisture sorption isotherm of the specimen, the value of A_{s, w} for the tightly bound water was estimated as a function of relative humidity. The results also enabled us to resolve the isotherm of each specimen into three components attributed to the tightly bound water, bound water, and loosely bound water.
The three components of the isotherm were discussed with reference to the analysis of the isotherm in terms of the B. E. T.'s multilayer adsorption of finite number of layers, n, deducing the following conclusions: 1) sum of the resolved isotherms of the tightly bound water and the bound water accords with the Langmuir's monolayer adsorption with n=1; 2) the resolved isotherm of the loosely bound water corresponds to the B. E. T.'s multilayer adsorption with n_max_??_n>1; but 3) no distinction between n_max_??_n>1 and n>n_max is achieved.