The Degradation of Cotton by Ionizing Radiation

Abstract

The effect of 60Co γ-radiation on physical and chemical properties of raw cotton has been studied over a wide dose range from 0 up to 120 Mrad. A variety of techniques—namely viscometry, infrared spectroscopy, solubility, analysis of stress- strain measurements, and scanning electron microscopy (SEM)—have been applied in an attempt to determine both micro- and macrostructural changes during irradiation. It was found that viscosity, ultimate strength, and ir data were in accordance with those published in the literature. Solubility data were quite different from those for purified cotton, and this has been attributed to the presence of wax in raw cotton. Small cracks almost parallel to the fiber axis started to be apparent by SEM from a dose of about 0.1 Mrad. At higher doses the cracks increased in number and enlarged in size and depth as well. This is probably due to the fracture of the interfibrillar bonds. Tensile fractography also showed differences between samples irradiated at different doses. Control cotton and low-dose-irradiated samples showed sharply- tapered fractures, while highly-irradiated samples showed blunt fracture ends. From the analysis of the data, it can be concluded that changes in cotton during irradiation were both intramolecular and supramolecular (interfibrillar) in nature.