The Effect of Oxidation on the Subsequent Oven Aging of Filter Paper
| Main Authors: | , |
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| Format: | Article |
| Language: | English Slovak |
| ISSN: | ISSN 0034-5806 |
| Online Access: | http://www.viks.sk/chk/res_1_95_10_30.doc |
| Abstract: | Summaries. It has been observed that oxidation of cellulose can affect the rate at which thermal chain scissions subsequently occur, an effect thought to result from the weakening of the chain at the site of the oxidized groups formed along the chains during the oxidation. This study examines the possibility that the number of such functional groups in excess of the chain ends formed during the oxidation provides an estimate of the weak links created along the chain that will break rapidly during subsequent thermal aging. In these experiments, filter paper that had been chemically or photochemically oxidized was aged in a humid oven. Scission kinetics during the degradation of the oxidized papers were measured and compared with that of unoxidized papers. For all papers except the most heavily oxidized, the magnitude of the early weak link scissions in the oven is comparable to the measured excess carbonyls produced during the oxidizing treatments. The oven aging of the oxidized sheets also demonstrated faster hydrolytic degradation even after the weak link period, which may be the result of increased acidity following oxidation of the cellulose. Conclusions. The research reported here was not designed to examine the after-effects of conservation bleach treatments, which would be formulated differently and would not be so severe. Rather, these studies are intended to explore the nature and consequences of other cellulose oxidation reactions, for example, atmospheric and photochemical oxidation. These processes not only have a significant tendency to degrade cellulose during oxidation but the result of the oxidation reaction seems to be a cellulose whose long-term stability may be compromised further in two ways. Modification of the cellulose chain creates weak links that seem more easily broken than links in the unmodified cellulose, and the amount of these weak links seems to be at least approximated by the excess carbonyls produced during the oxidation. Also, the oxidation can create acidity, which exacerbates the normal hydrolytic breakdown of the cellulose. An important implication of this study is the possibility that the degradation of a paper is determined not only by its acid content or cellulose DP but also by its content of such modified weak links, which essentially create a cellulose that may, at least for a time, tend to degrade more rapidly. Thus, just as fiber morphology and accessibility are known to affect the rate of hydrolytic degradation of cellulose, the presence of these modified groups can also alter the observed degradation rate of cellulose. As a result, there should be no presumption that two papers having equal cellulose DP and equal acidity will degrade at the same rate, and it is possible that the degree of oxidation of the cellulose may be an important determinant of the overall degradation rate. |
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| ISSN: | ISSN 0034-5806 |
