Plasmachemical Modification of Paper

The influence of the atmospheric air plasma treatment on the surface properties of paper was investigated. This contribution presents results of the surface energy evaluation and absorption evaluation of the paper material treated by the plasma. The contact angle measurement and the drop absorption test were employed as the surface characterising techniques. The treatment time and the power input were varied to observe the dependence of the surface properties on the plasma parameters. Furthermore the influence of the storage time on the paper surface properties was studied. Introduction Paper has been the main material for recording the cultural achievements all over the world since the invention of paper in 105 a.c. in China and expanzion of its production to whole Europe in 11 century [Ďurovič et al., 2000]. Paper due to the influence of wide range of agents undergoes different degradation processes that result in alarming conditions of most of the historical documents. The protection and preservation of paper-based artefacts from decay presents a serious problem for many libraries, archives and museums [Laguardia et al., 2005]. Paper consists mostly of bonded cellulose fibres that are linear polymers of glucose (β-Dglucopyranose) monomers linked by β-1,4-glycosidic bonds. Degree of cellulose polymerisation based on its origin is up to 15 000. All chemical reactions occure at hemiacetal and hydroxyl groups. These two determine the chemical properties of cellulose. 70 % of cellulose is in crystaline structure (fibres are crosslinked via intramolecular hydrogen bonds) and 30 % is amorphous. In addition to cellulose fibres, paper contains hemicellulose (wood polyoses), lignin and certain amount of additives, e.g., fillers, pigments, size and metal ions. The quality of the cellulose fibres, its morfology and its intramolecular structure influences paper properties, mainly the paper strength. Generally all degradation processes result in cellulose chain scission (reduction in polymerization degree) and thus decrease of paper strength. There are two main types of paper chemical deterioration: hydrolysis and oxidation. Cellulose degradation results in creation of D-glucose and/or low molecular products. Causes of deterioration may be either internal (type, quality and chemical composition of the pulp used for paper production, sizing, dyes and impurities) or external (temperature, relative humidity, air pollution, lighting conditions and biological agents). Paper degradation is always the result of both external and internal factors [Ďurovič et al., 2000]. Wide range of conservation and protection techniques was developed in order to prevent the paper deterioration. Most of these methods are based on chemical and mechanical principles. When applying chemical methods the influence of chemicals on paper properties and evniromental impact has to be taken in account [Laguardia et al., 2005]. In order to avoid these problems new techniques have to be studied. A new conservation method may be a plasma treatment which is a well established technique in a number of other processes (e.g. plasma coating, etching, cleaning, etc.). In recent years, the influence of low pressure plasma on biodeteriorat paper was studied [Laguardia et al., 2005; Vohrer et al., 2001]. Our research is focused on the influence of atmospheric air plasma treatment on the paper and its properties. Experimental Common office paper MultiCopy Original White (grammage 80 g/m) was used as a tested material [Stora Enso, 2005]. The samples were treated in the plasma reactor UPS 100 W based on the surface barrier discharge. The surface discharge is the non-equilibrium plasma supplied by the high AC voltage with the operation frequency of 7 kHz. The plasma power input was varied from 130 W to WDS'06 Proceedings of Contributed Papers, Part II, 162–166, 2006. ISBN 80-86732-85-1 © MATFYZPRESS