Effect of the fine structure and electrolytic contaminations on the specific conductance of some cellulosic materials

Abstract

SynopsisFrom dielectric loss measurements the specific conductance of some cellulosic materials of different fine structure free of and contaminated with electrolytic impurities in the temperature range of 283.15-333.15 K was determined. Also the activation energy of conductance for the different samples examined was calculated. Based on the data obtained and the discussion given, it is now possible to view the conductivity of the complex structure cellulosic substances in a much clearer light. INTRODUCTIONThe outcome of several investigations'-" reveals that the magnitude of electrical conductivity of polymeric materials is not strictly definite and invariable, but depends on several factors, mainly the presence of impurities, moisture content, and chemical composition. The problems pertaining to the dependence of the electrical insulating substances on each of these factors have been discussed, yet there remains an open question about the role played by the arrangement of elementary units and forces between them, especially when systems of complicated structure and of highly hygroscopic nature such as cellulosic fibers are concerned. To answer this question and to shed more light on the electrical conductivity of these materials, the conductivity of some cellulosic substances free of and contaminated with electrolytic impurities of different nature and magnitude will be determined. For the sake of comparison, the specific conductance of cellobiose, a 100% crystalline material and that of starch, a 100% accessible substance, will be also determined. In addition, some characteristic properties of the fine structure of the examined samples will be determined by measurements of x-ray diffraction, iodine adsorption, and degree of polymerization. EXPERIMENTAL MaterialsThe present investigation will be carried out on two sets of samples, namely A samples free from electrolytic impurities as judged from their undetectable ash contents and B samples with different nature and magnitude of electrolytic contaminations. The different samples investigated were prepared as given below. with redistilled water till free from acid. Under such experimental conditions, it has been pointed out"." that the acid removes all the inorganic contaminations from cellulosic fibers as well as from hydrocelluloses.Mercerized cellulose (11) was prepared from cotton cellulose following the previous work.', Viscose rayon (111) was prepared by purification of commercial viscose fibers following the same procedure as in case of sample.' Hydrocelluloses (IV, V, and VI) were prepared from cotton cellulose, mercerized cellulose, and viscose rayon, respectively, as before,14 in which the fibers were subjected to acid action by the use of 1 N HC1 at 100°C for 4 h, then washed with water until free from acid.Starch (VII) was a B.D.H. analar-soluble starch. Cellobiose (VIII) was an Eastman Kodak analar sample in the form of crystalline powder. SAMPLES B:Cotton cellulose (IX) composed of ash content of 0.3%, was prepared from medicated cotton cellulose a...