Kinetics of degradation of non-recycled and recycled contemporary paper

Paper is still regarded as the most common carrier of information. Encouraged by environmental policies, the papermaking technology recently changed, resulting in an increased production of recycled paper. Two types of contemporary paper, non-recycled and recycled, were thus investigated to evaluate possible differences in their rate of degradation. The analyses were carried out using unaged paper to evaluate acidity, dry matter and ash content, lignin presence, and fibre furnish. Accelerated ageing experiments were performed at different temperatures (50-80 °C) and water vapour pressures (90.5-227.5 torr). Viscometric measurements were carried out to evaluate the extent of paper degradation as a function of time, upon various accelerated ageing conditions. The results indicate that the rates of degradation follow first-order kinetics with respect to scission of glycosidic bonds, the rate constants for recycled paper being found to be slightly higher than the corresponding constants for non-recycled paper, but comparable within experimental limits. The kinetic constants did not display a monotonic trend with increasing water vapour pressures. The Arrhenius dependence of the rate constants on temperature for both kinds of paper supplied the activation energies, which fall in the typical range expected for paper degradation. Finally, the measured rate constants fit fairly well the recently modelled dose-response function for historic paper. Colour changes were found to be visible to the human eye for samples aged for more than 40 days at 60, 70 and 80 °C.