1H NMR Relaxation study of cellulose - water interactions in paper

The authors studied interaction between water and cellulose in laboratory paper prepared ad hoc in alkaline condition using H-1 NMR relaxation techniques. Since paramagnetic substances play a major role in NMR relaxation processes, EPR spectra were also studied. 1H NMR can give information on the interaction between cellulose and water coupled by a strong spin diffusion that can equalize Ti values. Measurements of the cellulose/total water molar ratio and the cellulose/bound water molar ratio result from the free induction decay. Free water content in groundwood paper is more than double for linter and kraft paper sheets. Performing a line shape analysis of the 1H resonance as a function of temperature provides information about the porosity of the system obtaining a scale of the distribution of pore diameter sizes. T-2 values of the water component depend on the amount and type of paramagnetic impurities that short T-2 values and the amount of free water. This parameter is therefore only useful for comparing paper from the same origin.