Influence of different oxidizing systems on cellulose oxidation level: introduced groups versus degradation model

Bleached cotton yarns were oxidized by potassium periodate and TEMPO-mediated oxidation systems, with different concentrations and treatment time, to obtain aldehyde and carboxyl oxy-cellulose with different oxidation levels. Oxidized celluloses were further treated with sodium chlorite to convert the created aldehyde to carboxyl groups. The oxidation level was evaluated by assessing the amount of introduced aldehyde and carboxyl groups, the changes in surface morphology and incurred degradation. Functional groups were determined by titration methods, while surface morphology by FTIR-ATR and SEM analyses. Degradation was analysed by determining the mechanical properties, degree of polymerization, alkali solubility and whiteness stability of the cotton samples. It has been established that a properly selected oxidation system, with appropriate working conditions, can provide satisfactory results for achieving low, medium and extensively oxidized celluloses, with a defined degradation profile. For a short treatment time, a higher oxidation level could be achieved by potassium periodate and TEMPO-mediated oxidation with sodium bromide, while by using the bromide-free TEMPO system a longer time was necessary to reach the same oxidation level. The type and oxidation level of the obtained oxy-celluloses influenced their mechanical properties, degree of polymerization, alkaline and whiteness stability. Low-level oxidized celluloses are suitable for producing stable, long-lasting materials with high added value, while extensively oxidized ones are more appropriate for developing disposable products. [GRAPHICS] .