Assessment of Selected Properties of Varnish Coating of Motor Vehicles

The technology and methods of testing the properties of varnish coatings used in motor vehicles are constantly and successfully developed. However, in the case of automotive varnish renovation coatings used in the repair of car bodies, the problem of fitting the quality of these coatings to the quality and current condition of the coating applied to undamaged vehicle components is not definitely solved. The main goal of the research was to determine the thickness and gloss distribution of the varnish coatings. The thickness and gloss of the varnish coating on the entire body of the vehicle were measured. Classical methods of assessing these properties were used. Defects in the renovation coating were also simulated, to show their negative impact on the varnish quality. The performed tests allowed for development of a procedure and algorithm for evaluation of the quality of the car’s renovation coating after the repair of the car body. The proposed procedure, expressed with the presented algorithm, allows to fit the obtained renovation coating to the quality and condition of the coating manufactured in factory on the car body in the range of its thickness up to 270 µm and gloss in the range of 5–90 GU. The developed procedure for the assessment of renovation coatings can be used in workshops that repair vehicle bodies. This will allow to improve the quality of renovation coatings and bring their properties, such as thickness or gloss, closer to those applied to the vehicle’s body at the factory.

Thermal Stability of Polyurethane Coating Prepared by Using Diphenylolpropane

Thermal stability on air of polyurethane varnish coating prepared from diphenylolpropane, polyetherpolyol and polyisocyanate was assessed. The presence of urethane groups, formed by phenolic hydroxyl of diphenylolpropane, in the polymer structure was shown to decrease its thermooxidative degradation onset temperature. At the same time, deceleration of thermooxidative processes due to stabilizing effect of diphenylolpropane released at the beginning of thermal decay of polyurethane is observed in the higher temperature region.

Growth of desert varnish on petroglyphs from Jubbah and Shuwaymis, Ha’il region, Saudi Arabia

Petroglyphs, engraved throughout the Holocene into rock varnish coatings on sandstone, were investigated in the Ha’il region of northwestern Saudi Arabia, at Jabal Yatib, Jubbah, and Shuwaymis. The rock art has been created by removing the black varnish coating and thereby exposing the light sandstone underneath. With time, the varnish, a natural manganese (Mn)-rich coating, grows back. To study the rate of regrowth, we made 234 measurements by portable X-ray fluorescence (pXRF) on intact varnish and engraved petroglyphs. Since many petroglyphs can be assigned to a specific time period, a relationship between their ages and the Mn surface densities (DMn) of the regrown material could be derived. This relationship was improved by normalizing the DMn in the petroglyphs with the DMn of adjacent intact varnish. In turn, we used this relationship to assign a chronologic context to petroglyphs of unknown ages. Following the removal of the varnish by the artist and prior to the beginning of Mn oxyhydroxide regrowth, a thin Fe-rich film forms on the underlying rock. This initial Fe oxyhydroxide deposit may act as catalyst for subsequent fast Mn oxidation. After a few decades of relatively rapid growth, the regrowth of the Mn-rich varnish slows down to about 0.017 µg cm–2 a–1 Mn, corresponding to about 0.012% a–1 Mn of the intact varnish density, or about 1.2 nm a–1, presumably due to a change of the catalytic process. Our results suggest that petroglyphs were engraved almost continuously since the pre-Neolithic period, and that rock varnish growth seems to proceed roughly linear, without detectable influences of the regional Holocene climatic changes.

Effect of Phosphoric Containing and Varnish-Coated Groups on Candida Albicans Adhesion and Porosity of Heat Cure Acrylic Denture Base Material

The aim of this study was to evaluate the effect of modified heat cured polymethyl methacrylate denture base (PMMA) or varnish coating of the denture base on candida albicans adhesion and porosity. First experimental group was prepared by addition of 15% phosphoric acid 2-hydroxyethyl methacrylate ester with polymethyl methacrylate monomer. While second experimental group prepared by varnish layer coating after material processing, these groups were compared with the control one. Three groups of vertex acrylic resin used as control, mPMMA and varnish coated group (PPH Cerkamed Wojciech Pawlowski, Poland). The inverted light microscope was used to measure the candida albicans adherence after one week and one month of processing. Two-way ANOVA, LSD test, T- test and Dunnett T3 were performed on data. Modified Acrylic resin showed highly significant reduction in candida albicans adhesion and porosity, also for varnish coating group showed highly significant reduction in candida albicans adhesion and porosity test.

Thermal insulation coating based on water-based polymer dispersion

For Russia, due to its long winter period, improvement of thermal insulation properties of envelope structures by applying thermal insulation paint and varnish coating to its inner surface is considered perspective. Thermal insulation properties of such coatings are provided by adding aluminosilicate microspheres and aluminum pigment to their composition. This study was focused on defining the effect of hollow aluminosilicate microspheres and aluminum pigment on the paint thermal insulation coating based on water-based polymer dispersion and on its optimum filling ratio. The optimum filling ratio was determined using the method of critical pigment volume concentration (CPVC). The optimum filling ratio was found equal to 55%.