Viera Jančovičová

Effect of UV light source intensity and spectral distribution on the photopolymerisation reactions of a multifunctional acrylated monomer

Abstract The goal of this study was to examine the possibilities of preparing thin surface spatial crosslinked polymer films by UV curing using 1,6-hexandioldiacrylate as a multifunctional monomer and 1-hydroxycyclohexyl acetophenone as a radical photoinitiator. Different UV light sources were used with different light spectral distributions and light intensities. It is found that the light source characterised at least by a particular overlap of its emission spectrum with the photoinitator’s absorption spectrum is the best system used for effective cure. Low polymerisation rate achieved in the case of smaller overlap of spectrums is easy to regulate by extending the energy of the emitted light.

Photochemical transformations of sodium anthracene-1-sulfonate in oxygen-saturated aqueous titanium dioxide suspensions

Abstract The decomposition of sodium anthracene-1-sulfonate (AN1S) by irradiation ( λ >300 nm) was investigated in oxygen-saturated aqueous solutions and TiO 2 suspensions. The concentration decrease of AN1S during exposure follows the formal first-order kinetics. The formation of phthalic and salicylic acids was monitored by high performance liquid chromatography (HPLC) in both photosystems. Additionally, the formation of alizarin during irradiation in the presence of TiO 2 was confirmed. The effect of experimental conditions (initial AN1S concentration, pH value, TiO 2 concentration) on the formal initial rate of AN1S photodegradation was studied in details. In situ EPR spin trapping experiments in TiO 2 suspensions confirmed the competitive reaction of photogenerated hydroxyl radicals between 5,5-dimethyl-1-pyrroline N -oxide (DMPO) spin trap and AN1S.

Photolysis of diaryliodonium salts (UV/Vis, EPR and GC/MS investigations)

Abstract The photodecomposition of commercial lipophilic diaryliodonium hexafluoroantimonate SarCat ® SR-1012 was investigated in acetonitrile (ACN) and ACN/H 2 O mixed solvents by means of UV/Vis spectroscopy, an EPR in situ spin trapping technique and GC/MS analysis. The application of the spin traps nitrosodurene (ND) and 5,5-dimethyl-1-pyrroline N-oxide gave evidence for the production of radical intermediates corresponding to the breaking of the carbon–iodine bond, in addition to carbon–oxygen bonds in SR-1012 aryl substitution. The photolytic products analyzed in aprotic acetonitrile were iodobenzene, acetanilide, biphenyl and C 12 H 25 CH(OH)CH 3 , while in ACN/H 2 O (1:1, vol.) solution iodobenzene, biphenyl, C 12 H 25 CH(OH)CH 2 OC 6 H 4 OH and hydroxylated biphenyls were identified. The influence of oxygen on the product distribution in both solvent systems was inconsequential. The proton concentrations photogenerated in the irradiated SR-1012 ACN/H 2 O solutions were quantified spectrophotometrically using bromophenol blue indicator.

Ink receptivity on paper — characterization of paper materials

Abstract The rheological behaviour of three black offset inks was tested using viscometer with the cone and plate geometry. The shear stress versus shear rate measurements confirmed that the investigated offset inks represent similar viscoelastic, pseudoplastic fluids, forming thixotropic structure. Mileage and ink transfer curves were measured onto the paper materials with different properties. The analysis of experimental results using Tollenaar–Ernst and modified Walker–Fetsko equations established the substantial role of the paper characteristics such as smoothness, brightness and penetration in the process of ink film formation on paper substrates during printing.

Impact of Stabilizing Procedures on Acidic Paper

Libraries and archives are confronted with progressive deterioration of their collections caused by paper degradation. We present a single-step treatment for acidic wood-pulp papers that includes a) removing soluble acidic products causing acid hydrolysis; b) preventing oxidative decay by introduction of an antioxidant agent; c) neutralizing free acids present in paper and forming an alkaline reserve to inhibit paper ageing; and d) improving mechanical strength by application of cationic starch. Zusammenfassung/résumé at end of article received: 13.10.2011 revised: 28.02.2012 179 DOI: 10.1515/res-2012-0008 ˇ ˇ

Influence of Deacidification on Arylmethane Dyes on Paper

Abstract The deacidification of historic paper objects has evolved into a method that is applied in mass-scale in some archives and libraries. While the impact of the deacidification reagents on paper is quite well researched, knowledge about the behavior of colours and dyes is more limited. Our study focused on the influence of paper deacidification by the Book Saver® process on eight different dyes applied on paper, as well as on the paper support itself. Accelerated ageing in moist and warm conditions (80°C, 65% relative humidity) was applied to investigate the stability of the dye layer on top of the paper, with respect to their chemical, optical and spectroscopic attributes. The Book® deacidification process increased the pH of the aqueous extract and an alkaline reserve was created. FTIR spectroscopic measurements showed that deacidification suppresses acid hydrolysis of paper. The variations in UV-Vis reflectance spectra and in total colour difference of the dye layer evidenced the changes in the structure of dyes caused by accelerated ageing, but the extent of the changes differs depending on the dye. We can conclude that some dyes are more prone to changes by deacidification than others.