Cellulose paper, aging

As acid paper ages, the amorphous regions of the cellulose fiber that are plasticized by water and/or humectant tend to disappear. The sorbi-tol/Kymene treatment becomes ineffective with degraded paper. This suggests that somewhat the same effect would be observed between new and degraded papers when humidified. Adrian Sclawy of the Library of Congress Preservation Research and Testing Office, carried out the experiments on humidification which are reported in Chapter 16 of this volume. 

The chain deterioration of cellulose during paper aging is irreversible and cannot be cancelled. A renevdng of the fibers is not possible but there are possibilities to stabilize brittle paper and the following measures are worthy of consideration ... 

A second degradation process is oxidation, often photo-induced especially by exposure to light not filtered for uv. The radicals resulting from this reaction promote depolymerization of the cellulose, as well as yellowing and fa ding of paper and media. Aging causes paper to become more crystalline and fragile, and this can be exacerbated particularly if the paper is subjected to poor conditions. 

Measurement of pH is a potentiometric technique frequently used for measuring the degree of the deterioration of materials that are subjected to natural aging. The determination of pH levels is commonly carried out on ethnographic objects manufactured with parchment or leather, and it is especially relevant in altered paper due to the formation of acidic compounds from the decomposition of the woodpulps and other raw materials, which can induce the hydrolysis of the cellulose and then decrease the resistance and mechanical properties of the document [29]. 

Early studies involved the development of a process which could treat all types of papers of varying ages and composition. Graft copolymerisation seemed to offer this potential. The basic concept of graft copolymerisation can be seen in Figure 1. Radical sites are created on the cellulose backbone and these sites allow the... 

Of the two test papers employed in this study, the wood pulp waterleaf better represents natural cellulose, while Foldur Kraft paper, which is sized with alum-rosin, is fifteen years old and also fairly acidic, more closely resembles average library book paper. Both the papers were aged as sheets freely suspended on a rack, as... 

While Barrow solved the main problem, there are other modes of degradation which must be considered. As an organic material, cellulose and paper can be easily oxidized. Very small amounts of the transition metals, compounds of iron, copper, and cobalt, under humid conditions can accelerate oxidation and embrittlement of paper. This type of degradation, as is shown later, does not show up in the dry-oven accelerated aging which Barrow used. Thus his alkaline papers, if they contained the oxidation catalysts, may not always have been permanent. 

Using the normal titration method on morpholine-treated paper samples, reserve alkalinity levels of less than 1% are found. However, in view of the previously mentioned possibilities for interaction between cellulose and morpholine and the observed reduction in the aging rate of morpholine-treated paper, it was thought likely that morpholine could be present in a form not immediately titratable but which might still offer some degree of protection against acid attack. 

Hernadi, S., Thermal Ageing in Oxygen of Paper Made from Cellulose... 

Natural or artificially accelerated aging of papermaking pulps is characterized by two important reactions, scission of the polymeric cellulose chains and some cross-linking reaction (7,8,9), the exact nature of which remains unknown. Since the mechanical properties of aged paper are modified by these two simultaneous reactions, it was of interest to determine whether these chemical effects influence the thermograms of artificially aged papers. 

In reviewing the literature on the effect of deacidification on paper, three important factors emerge (a) it is desirable to work with papers that are reproducible, well characterized, and similar in properties, both chemical and physical, to old papers (b) much more work needs to be done on the interaction of metals with the carboxyls in cellulose and (c) a standard procedure for accelerated aging that includes some moisture in the aging atmosphere is desperately needed. 

An increased degradation effect has been observed with an increase in the temperature at which cellulose was irradiated. Spirora and Flyate (88) observed that changes caused by UV radiation are about the same as those caused by thermal aging. Desai (89) reports that the wet strength of papers exposed to UV increases as does that of heat-treated pulp. Launer and Wilson (33), using irradiation at wavelengths of 330 nm to 440 nm, found that papers made of cotton and wood fibers with... 

Celluloses are similar to other linear polymeric materials in that they can possess one-dimensional order within an individual chain as well as three-dimensional order within an aggregate of chains. Increments in the levels of order occur during the isolation of native celluloses and also as a result of exposure to conditions that promote molecular mobility, such as elevated temperatures and immersion in plasticizing fluids. These increments generally result in embrittlement of the cellulosic materials. Similar effects are expected to occur upon aging of cellulosic textiles and papers over extended periods, and may be accelerated by hydrolytic cleavage of cellulosic chains. The implications of these effects for conservation practices, both with respect to recovery of function as well as in the assessment of deterioration, are reviewed. 

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