Evaluation of Thermal Degradation Kinetics of Hybrid Cellulose Acetate Membranes using Isoconversional Methods

Abstract

Cellulose acetate membranes are widely used in industry, emphasizing water purification processes, such as desalination. With some limiting mechanical properties, the synthesis of hybrid membranes appears as an alternative for developing high-performance materials. For its application, knowledge of thermal stability is crucial. In this work, the thermal degradation kinetics of AC-SiO2-(CH2)3NH2 hybrid cellulose acetate membranes are evaluated from thermogravimetric analysis, at three heating rates, 5, 10, and 20°C/min. The isoconversional methods proposed by Kissinger, Flynn-Wall-Ozawa, and Friedman were used for the present study of degradation kinetics. It was observed that insertion of silicon to polymeric structure promoted thermal stability to the membrane, presenting higher activation energy than pure cellulose acetate membrane, increasing from 240.28 to 1039.01 KJ/mol, using the method of Friedman. In contrast, the increase in nitrogen concentration decreases its thermal stability compared to the cellulose acetate membrane with incorporated silicon, reducing the activation energy from 1039.01 to 250.50 KJ/mol. However, it is more stable than the pure cellulose acetate membrane. The evaluation carried out in this study explained the influence of the minimum variation in the chemical composition against the thermal stability of hybrid membranes, being a factor of great importance for its application.