Thermal degradation and morphological studies on cotton cellulose modified with various arylphosphorodichloridites

Cellulose arylphosphonate compounds have been synthesized and investigated by the kinetics of thermal degradation by thermogravimetry (TG) and differential scanning calorimetry (DSC) from ambient temperature to 600degreesC. Various kinetic and thermodynamic parameters such as energy, entropy and free energy of activation have been obtained from TG curves using the Broido method and transition state theory. The high values of enthalpy change (1016 and 1025 J g(-1)) of decomposition and oxidation reactions corresponding to the last two exotherms of the DSC curves of cellulose are decreased to a greater extent in the case of cellulose arylphosphonate compounds. The values of activation energy for the decomposition stage of cellulose arylphosphonate compounds lie in the range 25-49 kJ mol(-1) and are found to be lower than that of pure cellulose, namely 165 kJ mol(-1) in air atmosphere. Scanning electron micrographs of phosphorylated cotton cellulose and chars show furrowed and fractured surfaces although the morphology of the original fibres remains largely unchanged. Furthermore, higher char yields of cellulose derivatives leads to the conclusion that such derivitisation may give rise to flame-retardant treatments for cellulosic materials. (C) 2004 Society of Chemical Industry.