| Abstract: | Summaries. Dry thermal ageing in the presence of air were applied to different alum-rosin sized wood pulp paper sheets. The change in the percentage of alum or adding sodium silicate in the sizing systems was carried out to vary the pH of the sample sheets in the range from 3.65 to 7.0. The changes in chemical composition, mechanical and optical properties, degree of sizing, in addition to the rate of glycosidic bond cleavage as a result of thermal ageing were measured. The results obtained show that neutral sized paper sheets have a higher optical and mechanical permanence compared with acidic sized papers. The polynominal models which correlate the time of ageing and pH's of sizing system with the mean values of optical changes or quality number of mechanical measurements were also proposed. |
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