Determination of the Cellulose Scission Route in the Hydrolytic and Oxidative Degradation of 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_94_26_45.doc |
| Abstract: | Conclusions. The combination of functional group and molecular weight analyses described here offers promise in characterizing the dominant scission chemistry of pure cellulose papers degraded in a variety of environments. Acid treatments produced equal numbers of scissions and carbonyls, the expected "reducing ends" produced by hydrolytic scission. A number of oxidizing treatments of this filter paper have been explored, and a range of degradation paths have been observed. These range from the non-scissioning carbonyl production of periodate treatments to the "random" oxidation of acidic hypochlorite, hydrogen peroxide and near-ultraviolet light. The variety of oxidative degradation suggests that the probability of post-oxidative strength loss, and the efficacy of stabilizing salt treatments, may strongly depend on the nature of the original cellulose oxidation chemistry. The results of tests on the same papers verify that the degradation chemistry in both humid and dry oven aging is almost exclusively hydrolytic. In the dry oven aging, the rate of hydrolysis is slowed enough to allow observation of contributions from other chemistries which produce carboxyl groups. This analytical approach holds the most promise in discriminating the dominant degradation path in systems capable of both hydrolysis and oxidation. For example, it is recognized that traces of certain metal ions can catalyze oxidation in paper, but at what concentration do these impurities cause the oxidative degradation to dominate the natural hydrolytic route? In a system where one paper is in contact with another rapidly oxidizing paper, is it the emitted volatile acids or oxidants that control the degradation of the adjacent materials? These and related questions are the subjects of future studies using this method. Summaries. The identification of the dominant cellulose degradation chemistry is of central importance to the design of effective paper preservation strategies. In order to discriminate different cellulose reaction paths, chemical analyses were chosen to monitor selectively and quantitatively both the scissions and functional groups produced in cellulose during paper aging. The results for acid-treated paper are consistent with hydrolytic scission, and humid oven aging also seems to degrade the cellulose by hydrolysis reaction. Dry oven aging shows the participation of other chemistries, although the dominant cellulose scission again appears to be hydrolytic. Oxidative treatments produced a variety of degradation behavior, ranging from the "specific" oxidation with periodate (carbonyl production with little chain scission) to the "random" oxidation of acidic hypochlorite and peroxide (3-4 carbonyls per scission). Compared with these "random" oxidations, exposure to near-ultraviolet light seems to be slightly more directed toward chain scission, with relatively little production of oxidation along the chains. These results suggest bounds on the post-oxidation strength loss that will occur due to subsequent "weak link" scission. |
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| ISSN: | ISSN 0034-5806 |
