Thermal Analysis of Acrylonitrile/Acrylic Acid Copolymer Dendrigrafted with Citric Acid

Abstract

Thermal analysis of acrylonitrile/acrylic acid P(AN/AA) copolymer films containing 5%, 10% and 20% acrylic acid dendrigrafted with citric acid (CA) is examined using differential scanning calorimetry (DSC) with various heating rates, thermogravimetry (TGA) and derivative thermogravimetric analysis (DTG). Also, the effect of carboxylic acid on thermal stabilization of the P(AN/AA) copolymers, when the carboxylic acid groups are in the bulk and when they are on the surface of the films dendrigrafted with CA, were studied using FTIR analyses. It is demonstrated that inclusion of carboxylic acid considerably enhances the rate of thermal degradation. The apparent activation energy (Ea) for overall cyclization and oxidation reactions is calculated using Kissinger's method. The results reveal that carboxylic acid, when used as a dendrigraft, influences the cyclization and oxidation process in a different way in comparison with when they are in the bulk. The activation energy of the first generation dendrigrafted P(AN/AA) copolymer was lower than that of the copolymer and the forth dendrigraft generation.