Dielectric measurements of cellulose and cellulose derivatives

The method of dielectric spectroscopy (DRS) is presented as analytical tool by demonstrating new measurement results of celluloses. The DRS determinat es the complex permittivity epsilon'(f) - i epsilon(f) in an extended frequ ency and temperature range by measurements of the impedance of a capacitor filled with the cellulose sample. In the low temperature range relaxation p rocesses are detected which are associated to the orientation motion of sid e groups at the repeating unit. Each of these relaxations is charaterized b y a relaxation time tau <-> (T), a relaxation strength Delta epsilon(T) and by shape factors as alpha(T) and beta(T). From the temperature dependence of the relaxation time the activation energy of the conformational motion o f the side group is determined. Different native celluloses, technical pulp s and viscose filaments are compared in their side group dynamics. Water an d ammoniak contents in cellulose increased the intensity and little affecte d the position in the time scale of the side group motion. in the middle te mperature range an additional relaxation is observed in wet and in with amm oniak activated celluloses whose intensity is, strongly affected by the con tent of the swelling medium. A careful drying of chemical pulps, which avoi d hornification, produce a characteristical variation in the side group dyn amics correlating with the chemical reactivity of the chemical pulp ina goo d manner.