Abstract
A heterogeneous method for the acetylation of cotton cellulose was used for the preparation of high-molecular weight cellulose triacetate. The rates of acetylation and degradation of cellulose using different catalyst (zinc chloride), concentrations at different temperatures were studied. Viscosity-concentration studies for solutions of cellulose triacetate in the solvents chloroform, methylene chloride, tetrachloroethane, formic acid and m-cresol were carried out. Molecular weight determinations were carried out osmometrically (Mechro-lab Model) using chloroform as a solvent, for cellulose triacetate samples in the molecular weight range of 30,000-150,000. The Mark-Houwink viscosity-molecular weight relationship for cellulose triacetate in the above solvents and the Huggin's viscosity-concentration relationship were investigated and the respective values of alpha, K and k1 constants were determined. The rate of degradation of cellulose triacetate in chloroform-acetic anhydride solutions for the catalysts sulphuric, perchloric acid, antimony pent chloride, ferric chloride, stannic chloride, tellurium tetrachloride and bismuth trichloride, were studied. The effect of catalyst concentration, acetic anhydride concentration and temperature (15°, 20°, 25°, 50° and 40°) on rate of degradation were investigated. An attempt has been made in this work to present the degradation results in terms of molecular weights instead of viscosity numbers as in previous work, so that theoretical equations for the degradation kinetics con be tested. A single-point method was used to relate the viscosity number with the limited viscosity number in a particular solvent mixture at a given temperature. Under the given conditions of solvent mixture and temperature K and alpha were evaluated and used in the Mark-Houwink equation to calculate the molecular weights.