The electrical conductivity of cellulosic derivatives in the presence of moisture

Abstract

The work presented in this thesis consists of a review of previous work on cellulosic materials and related polymers, and the results of an experimental investigation into the electrical conductivity of cellulosic derivatives (cellulose acetate, cellulose acetate butyrate) in the presence of moisture. The experimental work for the present investigation has been carried out in three parts. The first part concerns the preparation of thin films of cellulose acetate and cellulose acetate butyrate from the raw material using a casting technique. The second and major part of the experimental work concerns electrical measurements, including the measurement of dielectric constant dielectric loss and volume conductance under different conditions of humidity and contamination, etc. These follow the experiments made by Barker and Thomas on the effect of moisture and high electric fields on conductivity in alkali-halide doped cellulose acetate. The third and the final part of the experimental work deals with the sorption measurements, i.e. the sorption isotherms for the materials and their correlation with the electrical measurements. This part is incomplete. The results obtained are in agreement with the results of Barker and Thomas and the two materials have given similar results. However the work has been extended beyond the original work of Barker and Thomas and significant disagreement has been found with their work. In particular results obtained at different humidity do not support the theory proposed by Barker and Thomas. The surface conductance of the specimens was measured and was found to be negligible at all humidities. It is concluded that there is no surface conduction on these materials.