Quick determination of dielectric anisotropy of paper sheets by means of microwaves

This paper deals with a new type of method for determining the complex dielectric constant at microwave frequencies in about 30 s. This method determines the dielectric anisotropy and refractive index for optically opaque paper sheets. The dielectric anisotropy ascribable to the local motions of cellulose molecules is supported by electron microscopic observations and mechanical anisotropy. The angular dependence of the complex dielectric constant gives the degree of molecular orientation and the distribution of cellulose molecules in paper sheets. The direction of the average orientation of molecular chains can be inferred from the anisotropic data. It is also suggested that the cellulose molecules should be oriented on an average in the direction of long axis of pulp fibers. The accumulation of data for complex dielectric constant and refractive index at microwave frequencies gives an important chart for manufacturing the functional paper corresponding to needs.