Investigation of the degradation of contemporary papers aged at different conditions of temperature and relative humidity

As the technical revolution in the paper-making industry, which took place between 1850 and 1950, led to a dramatic chemical destabilisation of paper materials, there has been a growing interest in paper degradation studies in the last decades. Although the mechanism and the rate of degradation have been studied extensively for historic papers, it seems that less attention has been given to real contemporary papers so far. Currently, the main structural component of modern paper is a felt of cellulose fibres from different origins (e.g., hardwood, softwood, grass, bast, recycled fibres), with the addition of other compounds (sizing, fillers etc.). Due to environmental issues, there has been a significant increase of recycled paper as fibrous component of print paper over the last years. Our research is mainly focused on the degradation of contemporary paper obtained by accelerated ageing experiments, exposing the samples to extreme conditions in terms of temperature (T) and relative humidity (RH), in order to develop a dose-response function. The samples studied in this research consist of two kinds of contemporary papers, substantially different from each other: pure cellulose papers that meet the ISO9706 standard specifications, and recycled papers with different percentages of recycled materials. Along with the determination of the fibre components of the papers by fibre furnish analysis and the detection of lignin by phloroglucinol tests, the degradation of the paper samples during the ageing tests are analysed in terms of pH, measured with the cold extraction method, and degree of polymerisation (DP), determined by viscometry in cupriethylenediamine solvent. These data allow to evaluate the extent of degradation of contemporary papers through a dose-response function. The elaboration of these results will lead to a comparison with the dose-response functions already modelled and/or to new dose-response function for contemporary papers