In order to take measures for preventing degradation of paper whose permanence is low, like acid paper, and saving them in a better state for a long time, it is preferable to estimate the natural ageing rate of various types of papers and to predict their life expectancy. Conventionally, the permanence of paper is evaluated by artificially ageing paper at a single temperature, but it has been reported that if paper deteriorates differently at different temperatures, the assumed permanence of paper at a single high temperature will differ from that at room temperature.
Thus, in this research, 11 naturally aged books from the Journal of the Chemical Society published in Britain that had deteriorated over time for 130 to 80 years were selected and further aged artificially under 4 temperature conditions between 60 and 90°C (65% r. h. constant). It was possible to obtain the degradation rates of tear index, burst index, degree of polymerization and discolouration at room temperature by Arrhenius plots with high correlation coefficient (more than 0.97). Initial physical properties were calculated by estimated degradation rates, current physical properties and time that elapsed from the publication of the sample books. The degradation rate indicator (degradation rate constant divided by tear or burst index) were calculated as in our previous research, since the higher the physical properties, the lower the degradation rate of tear or burst index was. Better correlation was observed between the concentration of hydrogen ion before moist heat accelerated ageing and the degradation rate indicator of the physical properties of paper at room temperature than at higher temperature.
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