Paper Conservation Using Aqueous Solutions of Calcium Hydroxide/Methyl Cellulose The influence of accelerated ageing temperature on properties of treated paper
| Main Authors: | , |
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| Format: | Article |
| Language: | English Slovak |
| Online Access: | http://www.viks.sk/chk/res_3_03_178_188.doc |
| Abstract: | SUMMARIES. On the basis of results obtained by the accelerated ageing of papers made of bleached softwood and rag cellulose the apparent activation energies of cellulose degradation were estimated as being 103 and 106 kj/mol respectively. The temperatures of 40° and 60°C were found to be inappropriate for the study of cellulose degradation in samples treated with Ca(OH)2 or Ca(OH)_)+MC conservation solutions because there were'no observable changes in the number average degree of polymerisation. The results obtained showed that a decrease in the strength of paper sheets treated by the named solutions during accelerated ageing was caused by the degradation of the methyl cellulose. A larger alkaline reserve in paper after treatment provided better protection of cellulose from hydrolytic degradation. The increase of untreated bleached softwood sulphite paper strength at 40° and 60°C was the result of hornification, which was caused by hydrogen bonding rather than by covalent bond crosslinking. CONCLUSION. Activation energies of 103-106 kj/mol were found for cellulose degradation in papers from bleached sulphite and rag cellulose, respectively.Treatment with Ca(OH)2 or Ca(OH)2+methyl cellulose aqueous solutions of these papers did not result in observable changes in DPn of cellulose after accelerated ageing at 40° and 60°C. This means that accelerated ageing at these temperatures is inappropriate for the study of cellulose degradation in papers treated with alkaline conservation solutions. The homification of cellulose in paper made from bleached sulphite pulp after accelerated ageing at low temperatures resulted in an increased fibre and sheet strength.The decrease of paper sheet strength in the case of paper treated by Ca(OH)2+ methyl cellulose conservation solutions arose from the degradation of the methyl cellulose rather than the degradation of the cellulose itself.The greater alkaline reserve in paper after treatment with Ca(OH)2+methyl cellulose aqueous solution provides better protection of the cellulose against hydrolytic degradation. |
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| ISSN: | ISSN 0034-5806 |
