Assessment of chromophores in chemically treated and aged wood by Uv-Vis diffuse reflectance spectroscopy

The optical properties and degradation of fir wood treated by different inorganic salts, which are components of waterborne wood preservatives, were studied before and after wet-thermal accelerated ageing (T=85 °C, RH=65%, for 30 days) using UV-Vis diffuse reflectance spectroscopy. The colour of all impregnated samples was due to the same chromophoric structures, thus revealing that the primary reactions leading to colour changes are essentially very similar. These chemically treated as well as standard (non-treated, unaged) and reference (treated only with distilled water, unaged/aged) samples have a significant absorption band at 358 nm, along with a shoulder near 265 nm of various intensity. The broad band at higher wavelength is attributed to the chromophoric structures derived especially from lignin, i.e. quinones, stilbenes, charge transfer complexes causing a bathochromic shift and other conjugated carbonyl structures. Coniferaldehyde is also a major contributor to this absorption. The band at 265 nm belongs to chromophores arising predominantly from carbohydrate degradation products, i.e. furan derivatives, quinone-type derivatives, catechol structures. Catechol structures (colourless) form coloured complexes with transition metal cations (Cu2+, Fe3+) or are oxidized to form highly coloured benzoquinone structures. Alkaline solutions of borax cause the reduction of conjugated and non-conjugated carbonyls and the degradation of coniferaldehyde. Generally, after ageing, the samples show higher absorptions in the visible region of the spectra in comparison with the unaged ones, which explains their yellowing and loss of brightness after the action of elevated temperature and moisture

Vliv vybraných účinných sloučenin z éterických olejů na ochranu papíru

The aim of this study was to assess the influence of selected compounds present in essential oils- EOs (linalyl acetate-LA and citral-C) and the accelerated ageing process on the chemical (cellulose degree of polymerization, content of saccharides), mechanical (tensile index) and physical (fibres length distribution) properties of papers. LA and C were evaluated as the compounds with the highest antimicrobial activity and therefore, they were applied into the paper mass in form of their vapours.Cílem této studie bylo posoudit vliv vybraných sloučenin přítomných v esenciálních olejích - EO (linalyl acetát-LA a citral-C) a zrychlený proces stárnutí na chemické (stupeň polymerace celulózy, obsah sacharidů), mechanické (index pevnosti tahu) a fyzikální vlastnosti (distribuce délky vláken). LA a C byly hodnoceny jako sloučeniny s nejvyšší antimikrobiální aktivitou, a proto byly aplikovány do papírové hmoty ve formě jejich výparů

Změny chemických a fyzikálních vlastností papírových dokumentů během přirozeného stárnutí

The aim of this study was to assess the changes in chemical and physical properties of selected paper documents, dating from the 18th century to the present date.Cílem této studie bylo posoudit změny v chemických a fyzikálních vlastností vybraných papírových dokumentů, pocházející od 18. století až do současnosti