Cellulose paper deterioration

The main cause for paper deterioration in libraries and archives is the acid catalyzed hydrolysis of cellulose, the ingredient that gives permanence to the paper. The aging permanence of paper is closely coimected with the add concentration in the paper. The priority in preservation measures is in most cases the dead-dification of acid paper. Today, more than 70 years after Barrow s pioneering work, mass deacidification of books and archive materials has become a commerdal reality. 

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]. 

A few animals (especially ruminants and termites) are able to metabolize cellulose, but even these animals depend on appropriate microorganisms in their intestinal tracts to hydrolyze the -1,4 links other animals, including man, cannot utilize cellulose as food because they lack the necessary hydrolytic enzymes. However, such enzymes are distributed widely in nature. In fact, deterioration of cellulose materials —textiles, paper, and wood —by enzymatic degradation (such as by dry rot) is an economic problem that is not yet adequately solved. Efforts to turn this to advantage through enzymatic hydrolysis of cellulose to glucose for practical food production have not been very successful (see Section 25-12). 

Feller RL, Lee SB, Bogaard J (1986) The kinetics of cellulose deterioration. In Needles HL, Zeronian SH (eds) Historic Textile and Paper Materials Conservation and Characterization. Advances in Chemistry Series 212. ACS, Washington DC, p 329... 

The potential permanence is built into paper at the time of manufacture it is determined by the materials used and the processes of manufacture. Three important factors are recognized (1) deterioration of the cellulose fibers prior to manufacture into paper and the presence of noncellulose components (2) the introduction of additives (sizing, loading, etc.) to the papermaking stock and (3) the presence of deleterious impurities originating from the fiber furnish, additives, process water, and mill equipment. 

When increasing demands for papermaking fibers in the 19th century led to introduction of cellulose fibers from wood as a more abundant source, it became evident that the wood fibers did not possess all the qualities of cotton fibers. For many years, cotton was considered the first choice for fibers in the manufacture of permanent papers, whereas wood fibers were considered less suitable. It was observed that many papers (particularly book papers) of relatively recent manufacture deteriorated so rapidly as to be useless after no more than a few decades. 

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. 

Acidity has long been recognized as a major factor contributing to the deterioration of cellulose-containing materials. In an effort to combat the harmful influence of acidity, researchers have developed a variety of deacidification techniques capable of decreasing the acid content of most paper-containing objects that are found in museums and libraries. These techniques often are used by conservators in the care of books and works of art on paper (I). Nevertheless, the nature of the chemical processes that cause papers to yellow and to lose strength remains somewhat obscure, and the role of acidity in these processes also is not well understood. 

Oxidation and acid hydrolysis are the two principal deterioration mechanisms for paper, and recently chemiluminescence (CL) has been used to follow the oxidation of cellulosic materials at temperatures of 40 °C and below (I). CL is thought to be produced by the termination... 

The paper and textile industries have been concerned about the aging, deterioration, and degradation of cellulosic materials at elevated temperatures for practical reasons, such as the performance of tire yarn and electrical insulation paper, and the problems involved in drying or processing the cellulosic materials in general. However, due to the practical nature of these problems, the reactions involved have often been measured in terms of loss of strength and other physical properties. 

The deterioration of paper in books and documents has been a concern for many years. Research by paper conservators indicates that books and manuscripts may be protected from aging by treatment with alkaline agents viiich neutralize the acidity of the paper as it develc s (3,, , 6,2). ie deaoidification process not oily neutralizes the acTdity of the oxidized cellulose, but also leaves an "alkaline reserve" in the paper to retard future deterioration. 

USE To impart pearly surface to cellulose-base, polystyrene, and phenol-formaldehyde resins, Deutsch er of.. U.S. pat. 2,816,044 (1957 to Brit. Resin Prods.). In heat -sensitive coating for copying paper, Van Dam, (J.S. pat. 2,897,090 (1959 to Anken Chem. Film). To stabilize tolylenedi-amme mixtures against deterioration and discoloration. Powers, US. pat. 3,138,641 (1964 to Mobay). 

Aluminum sulfate and similar acidic compounds mixed with materials such as clay and rosin are added to paper to improve its printing characteristics. However, the acids decompose the cellulose fibers in paper, causing the paper to deteriorate over time.The Library of Congress estimates that 25% of its collection is brittle from such deteriorating paper.Calcium carbonate,a basic substance,has been suggested as an alternative in preparing paper. 

The use of a portable NMR device allows a non-invasive investigation of paper to assess the state of conservation of books and documents of historical or artistic interest. The NMR investigation focused on relaxation measurements whose results seem compatible with different relaxation rates in crystalline and amorphous cellulose domains. By a simplified physical picture based on spin-diffusion it appears possible to detect the alteration of the crystalline/ amorphous cellulose balance and therefore to get information on deterioration processes of paper. ... 

Polymers have been shown to affect the deterioration of objects where they have been studied, e.g. paper (Baer et al., 1976), canvas (Berger and Zeliger, 1975) and metals (Williston, 1982). The object can in principle make an enormous difference to the ageing behaviour of the applied polymer. However, this seems to have been noticed in only a few cases. Most objects in conservation are old ones and have themselves started to degrade to some extent. Cellulose rapidly... 

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