Paper Conservation Using Aqueous Solutions of Calcium Hydroxide/Methyl Cellulose The influnce on the degradation of papers
| Main Authors: | , |
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| Format: | Article |
| Language: | English Slovak |
| ISSN: | ISSN 0034-5806 |
| Online Access: | http://www.viks.sk/chk/res_1_04_15_25.doc |
| Abstract: | SUMMARIES. Bleached softwood bisulphite and alum-rosin sized rag paper samples were subjected to conservation treatments with calcium hydroxide and with calcium hydroxide - methyl cellulose solutions. Accelerated ageing at 90°C and 50% RH was done in order to evaluate the influence of these treatments on several paper qualities: degree of polymerisation, wet zero-span tensile index, tensile strength, ISO-brightness, pH of the cold extract and alkaline reserve. The depolymerisation of the cellulose of the papers at the initial stages was explained by the first-order kinetics of the Ekenstam model. The influence of the conservation treatment on the life expectancy of the treated papers was evaluated. It was concluded that the main reason for tensile strength decrease in bleached softwood bisulphite paper treated with methyl cellulose was the degradation of this compound during accelerated ageing. CONCLUSIONS. The depolymerisation of the cellulose of the untreated papers and those treated with Ca(OH)2 or Ca(OH)2+MC conservation solutions, can be described by the first-order kinetic or the Ekenstam model at the initial stages of the depolymerisation. Treatment with these solutions increased the life expectancy of bleached bisulphite paper studied by a factor of 8 and 21 respectively. For rag paper sized with aluminium resinate these factors were 2.7 and 3. The existence of degradation mechanisms other than acid hydrolysis was confirmed by the continuous decrease of DPn of all the treated papers. The tensile strength increase for untreated and Ca(OH)2 treated bleached bisulphite paper at the beginning of accelerated ageing can be explained by a hardening. The degradation of the methyl cellulose during accelerated ageing was concluded to be the main reason for the tensile strength decrease in bleached bisulphite paper treated with Ca(OH)2+MC solution. |
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| ISSN: | ISSN 0034-5806 |
