Kinetics of the acid‐catalyzed degradation of cellulose esters

Abstract

AbstractThe acid‐catalyzed degradation rates of cellulose acetate and cellulose propionate in acetic and propionic acids and anhydrides have been determined by repeated viscosity measurements. Relative degradation rates could be estimated with the aid of a standardized curve that related intrinsic viscosity to extent of degradation under the assumption of pseudozero‐order degradation kinetics. Degradation rates were established as functions of temperature and concentrations of water, sulfuric acid, and aliphatic anhydrides. The most surprising result was that the degradation of cellulose acetate passed through a minimum as a function of acetic anhydride concentration, whereas the degradation rate for cellulose propionate always increased with acetic anhydride or propionic anhydride concentrations. A mechanism is offered in terms of steric interaction between ester groups on the cellulose and various acidic species.