Thermal and spectroscopic studies on C-2, C-3 and C-6 substituted cellulose with different groups

Abstract

The thermal behaviour of cellulose and its C-2, C-3 and C-6 derivatives substituted by acetyl, benzoyl and trityl groups has been studied in a static air medium by differential scanning calorimetry and thermogravimetry from ambient temperature to 450 ° C. Various reactions involved viz. dehydration, deacetylation, debenzoylation, detritylation, oxidative decomposition and oxidation of charred residues are discussed. Thermodynamic functions for different stages of thermal degradation are obtained from TG curves using the method of Broido. The activation energies for cellulose and its C-2, C-3 and C-6 substituted derivatives are found to be in the range 136 to 253 kJ mol −1. The IR spectra of these derivatives indicate formation of a compound containing CC and CO groups in the final residual char. The EPR signals indicate the formation of trapped and stable free radicals in the degradation of the compounds. Cellulose benzoate and its subsequent substituted derivatives show generation of a large amount of trapped free radicals during the decomposition. The mechanism of acid-catalysed thermal degradation of cellulose esters is proposed.