Investigations of the kinetics and effects of degradation of paper-based materials

In the digital era, paper is still regarded as the most widespread carrier of information. The present doctoral thesis deals with the kinetics and effects of paper degradation, investigating this undesired but inevitable process from three points of view. (I) Two types of contemporary paper, non-recycled and recycled, were characterised and aged at different temperatures and humidity levels to evaluate their rates of degradation. The variations of degree of polymerisation (DP) as a function of time for both papers were found to follow the rate law described by Ekenstam. Rate constants (k) and activation energies of both papers were found to be comparable within experimental limits. Interestingly, k did not display a monotonic trend with increasing humidity. (II) The effects of γ-irradiation as disinfection treatment, whose applicability to library materials is still debated, were evaluated. Pure cellulose paper samples were exposed to two doses of γ-rays (5 and 10 kGy) and additional treatments (drying and ageing). Although mechanical properties were only slightly affected, a notable decrease of DP was found for the irradiated samples. γ-rays caused small colour changes, larger changes being caused by the synergetic effects of ageing. (III) Unlike the above-mentioned studies which involved destructive methods, an innovative non-destructive and non-invasive collection survey was conducted at an historical Italian library to evaluate the current and future conservation state of the collections. About 300 items, dated from the 14th to the 20th century, were analysed by assessing physical degradation visually and by modelled NIR data, which provided the main chemical and physical paper properties. The results are generally consistent with the development and chronology of European papermaking. Further elaboration of pH and DP data using damage functions provided the predictions of the degradation rates of the items in different environmental storage conditions, useful to inform future preservation policies.