The Influence of Secondary Chromophores on the Light Induced Oxidation of Paper Part II: The Influence of Light on Groundwood Paper
| Main Authors: | , |
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| Format: | Article |
| Language: | English Slovak |
| ISSN: | ISSN 0034-5806 |
| Online Access: | http://www.viks.sk/chk/res_2_03_118_132.doc |
| Abstract: | SUMARRIES. The samples in our research were different kinds of paper, to which chromophores, i.e. oxidative degradation products of groundwood papers were added. In the first part several parameters of pure cellulose paper were checked, for the second one papers which already contained those degradation products, i.e. just the very groundwood papers from which the added degradation products were extracted were studied. We were mainly interested in the changes provoked by light with both high and reduced levels of UV. Finally, some recommendations are given as to how to preserve and exhibit groundwood papers, including those which have been deacidified using a solution of methanolic methyl magnesium carbonate. CONCLUSION. ˙ VIS radiation has a crucial influence on the creation of carbonyls in ground-wood paper, which is to be seen as the first stage of light induced oxidation. ˙ UV radiation influences the creation of extractable degradation products in groundwood paper, i.e. the second stage of light induced oxidation. ˙ Both UV radiation and VIS radiation have an influence on the yellowing of groundwood paper. ˙ A UV filter does not stop the initiation of light induced oxidation, where VIS has a crucial influence, but it significantly prevents or at least decreases the disintegration of lignin, the creation of acid and of coloured degradation products. ˙ A UV filter considerably reduces the creation of coloured degradation products significantly slows down the yellowing of paper and the creation of acidity. ˙ The creation of carbonyls (first stage of oxidation) in deacidified groundwood paper is considerably more influenced by UV radiation than in non-deacidified groundwood paper. A UV filter only partly inhibits this process, probably by reducing the creation of radicals. ˙ Mg bound to lignin structures during deacidification plays a part in the decrease of paper brightness. It significantly inhibits light induced oxidation of groundwood paper in an alkaline medium. ˙ Mg bound to lignin structures as a result of MMMC deacidification plays a part in the decrease of paper brightness. It significantly inhibits the formation of carbonyls, but contributes to reduced brightness (yellowing) and to the creation of extractable agents. ˙ The alkaline environment brought about by MMMC deacidification significantly supports the degradation of lignin and the creation of extractable agents, and in the case of a primarily neutral paper this happens quite dramatically. ˙ For long-term storage of deacidified groundwood papers (MMMC application) it is very important to eliminate both radiation components from illumination. ˙ For long-term storage of groundwood papers it is particularly necessary to eliminate VIS radiation, which initiates light induced oxidation, but also UV radiation, which causes further disintegration. |
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| ISSN: | ISSN 0034-5806 |
