KINETIC-STUDIES ON THE ACCELERATED AGING OF CELLULOSIC MATERIALS

The natural aging of cellulosic materials (high purity paper, cotton, raw and bleached flax, viscose) was simulated by thermal oxidation in air at constant temperature (123-192 degrees C). Also the synergetic e ffect of light was investigated at 50-85 degrees C. The kinetics of po lymer degradation was followed through intrinsic viscosity measurement s and was correlated with the degree of crystallinity, determined by X -ray diffraction, and with the surface oxidation of the investigated s amples, evaluated through XPS analysis. At least two constant rate sta ges were observed in kinetic runs. The acceleration factors and time n ecessary for simulating a 20-year thermal aging of the investigated ce llulosic materials were obtained from the calculated activation parame ters by extrapolation of the process rate coefficients to room tempera ture. Surface oxidation parallel to aging led to the formation of low- molecular-weight, easily removable products in pure cellulose material s, while in lignin-containing materials mainly lignin was involved.