Paper Ageing: The Effect of Paper Chemical Composition on Hydrolysis and Oxidation

The degradation of cellulose is an important factor influencing its mechanical, optical, physical, and chemical properties and, hence, the lifetime of paper in libraries and archival collections. Regardless of the complexity of the paper material, the main chemical pathways for its degradation are hydrolysis and oxidation. This study presents an overview of the analytical techniques employed in the evaluation of the hydrolysis and oxidation processes; these techniques include size-exclusion chromatography, Fourier-transform infrared and ultraviolet–visible spectroscopy, and X-ray diffraction. This paper aims to determine the extent to which these instrumental methods are useful for studying the aforementioned processes and for which lignin contents. It also highlights how atmospheric humidity could affect the cellulose structure in paper containing lignin. It was found that humidity causes significant changes in the cellulose chain lengths and that a high lignin content in paper could suppress some cellulose degradation pathways. This knowledge can be applied to developing strategies and selective chemical treatments preventing the consequences of paper ageing.

Oil Aging due to Partial Discharge Activity

<p>Oil is the main insulation in power transformers and over long time of ageing its insulation properties can change. In this paper ageing of oil due to the exposure to electric discharges was investigated. The effect of high energy discharges (complete arc) and low energy discharges (partial discharges) on oil properties such as breakdown strength and oil conductivity was investigated.<br />An experimental setup consisting of two spherical electrodes was designed. The adjustable distance between the two electrodes made it possible to have PD with different magnitude.<br />The oil conductivity and breakdown strength was measured for three sets of experiments. The first group of experiments was performed on new oil in order to have a reference for comparison. In the second group of experiments the new oil samples was exposed to 1000 and 3000 lightning impulses. In the third group of experiments new oil samples was exposed to partial discharge for different duration of time. Oil conductivity and breakdown strength of these aged samples were compared with new oil. The results show that after exposure to lightning impulse oil conductivity increases and breakdown strength decreases, However PD activity for short time does not change the oil conductivity but it reduces the breakdown strength.</p>

The Effect of Light on the Changes of White Office Paper

Light, primarily its more energy-rich component - near ultraviolet radiation, causes gradual degradation (ageing) of paper and other organic based materials. The objective was to determine selected characteristics of the changes of white office paper, which occur under intensive ultraviolet treatment, and to calculate their light fastness, as this is an important functional feature for the number of papers. The most visible sign of paper ageing is the change of its optical characteristics. The value of specific lightness decreased by 2.2%, red / green coordinate a* moved from the red region (1.5) colour space to green (-0.8), b* coordinate moved from the blue region (-8.4) to yellow (4.7) and colour difference ΔE* reached 13.4 during 120 minutes' exposure. The pH values of paper surface gradually decreased with time of UV exposure from 8.86 to 7.91. Effects of light also deteriorated the selected mechanical characteristics of paper, such as breaking length and tear index. Out of the monitored properties, the specific lightness of paper surface showed the greatest stability (97.8%). UV radiation most affected breaking length of paper whose stability was only 79.4%.