Thickness-sensitive, spectrally selective paints based on a silane treatment of pigments were prepared with different pigment-volume concentrations. The critical pigment-volume concentration was ...determined by means of electrochemical impedance spectroscopy, while the pigment particle size distribution was determined with ultrasound spectroscopy. The selectivity versus thickness relation of a paint with a near-critical pigment-volume concentration was studied spectroscopically through performance criteria. Its nonlinearity was shown to be related to the surface topography. This relation was further supported by hydrophobicity measurements. Heat-gathering tests in a simulated solar collector supported the spectroscopic determination of an optimal dry-film thickness.
High solid (HS) alkyd resins with low amount of volatile organic compounds (VOC) were developed as the result of new VOC solvent directive that limit the amount of VOC in decorative paints. Due to ...specific chemical structure of HS alkyd resins and possible deterioration of some applicative properties the optimal combination of driers is an important subject of research. In our present work we studied the influence of iron (Fe) and cobalt (Co) surface driers with strontium (Sr) through drier on the film formation of HS alkyd coatings. The kinetics of autoxidation was analysed using FT-IR spectroscopy. Further, applicative properties like drying time and film hardness were examined. In the end, electrochemical impedance spectroscopy (EIS) was used to evaluate the quality of cured HS alkyd coating films after exposure in the humidity chamber. It was established that the addition of the Sr drier to surface driers accelerates the film formation process. As higher amounts of the Sr drier were added, final drying times were reduced and film hardness increased. The highest quality of cured films were observed for Co/Sr and Fe/Sr drier combination at 1:1 concentration ratio.
The aim of this study was to be able to reversibly bind histidine-rich proteins to the surface of maghemite magnetic nanoparticles
via coordinative bonding using Zn ions as the anchoring points. We ...showed that in order to adsorb Zn ions on the maghemite, the surface of the latter needs to be modified. As silica is known to strongly adsorb zinc ions, we chose to modify the maghemite nanoparticles with a nanometre-thick silica layer. This layer appeared to be thin enough for the maghemite nanoparticles to preserve their superparamagnetic nature. As a model the histidine-rich protein bovine serum albumin (BSA) was used. The release of the BSA bound to Zn-decorated silica-coated maghemite nanoparticles was analysed using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). We demonstrated that the bonding of the BSA to such modified magnetic nanoparticles is highly reversible and can be controlled by an appropriate change of the external conditions, such as a pH decrease or the presence/supply of other chelating compounds.
In recent years, many efforts are being devoted to the development of new materials that originate from renewable resources. Polyesters are one of the most important classes of such materials and ...several bio-based monomers are available for their synthesis. In this work, the development of fully bio-based and solvent-free polyester polyol used for two-component polyurethane coatings on industrial scale is presented. Fossil-based raw materials were substituted with bio-based alternatives that are commercially available on a large scale. Properties of polyols and coatings were determined and measured. Polyols were characterized by the determination of acid number, hydroxyl number, glass transition temperature and refractive index, and measurement of viscosity, color and molecular weight. Coatings were characterized by the determination of mechanical properties, such as hardness, elasticity and impact resistance, and the measurement of optical properties such as gloss, haze, distinctness of image (DOI) and reflected image quality (RIQ) and weathering resistance. Three variations of bio-based polyol were synthesized, then the most suitable version was validated in a clear coat. The results showed that the properties of the bio-based polyol and coating met the requirements and were comparable to the properties of the synthetic counterpart. Results indicate that this newly developed 100% bio-based and solvent-free polyol can be used as a drop-in replacement for synthetic polyol. Furthermore, this work implies that the supply chain is established which allows the green transition in the paint industry.
•Organically modified clay was successfully swollen in 2-(1-methoxy)propyl acetate.•Interlayer spaces between clay platelets in nanocomposites are 3.61–3.76nm.•Clay platelets in nanocomposites are ...about 100nm in length and 50nm in width.•Water uptake of nanocomposites at clay content between 1 and 4% (w/w) are reduced.•Amount of diffusion through nanocomposites film is decreased for a decade.
Polyacryl–nanoclay composites are new class of materials obtained by dispersing montmorillonite clay nanoplatelets (nanoclay) into the polymer matrix. In present work we investigate and confirmed that montmorillonite nanoclay significantly enhances barrier properties of acrylic composite. Two stage of dispersion process was used to prepare polyacry–nanoclay composites. Different percentages of montmorillonite clay nanolayers were added to polyacryl dispersion and applied on steel panel with 0% (w/w), 1% (w/w), 2% (w/w) and 4% (w/w) of nanoclay as composites. Performance of nanoclay intercalation in polyacryl composite was measured by X-ray diffraction (XRD) and the structure characteristics of samples were analyzed with transmission electron microscopy (TEM). The effectiveness of prepared nanocomposites was identified by the hardness measurements and mechanical properties. Further anticorrosion characteristics, especially barrier properties were indirectly detected by electrochemical impedance spectroscopy (EIS). This method was also used for the determination of montmorilonite nanoclay optimal concentration in acrylic composite where optimal barrier properties were achieved.
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•Properties of low and high density polyethylenes under pressure of CO2 and propane.•Phase transitions of low and high density polyethylenes under pressure of CO2 and propane in ...pressure range from 0.1 to 90MPa.•Solubility and diffusivity of CO2 in low and high density polyethylenes by magnetic suspension balance (MSB).•Thermal analyses of unprocessed and grinded polymers and polymers after exposure to CO2 by DSC.
The aim of this work was to investigate the properties of polyethylenes (PE) of various densities (low-density and high-density) under pressure of CO2 and propane. The phase equilibria of PE of different density in presence of CO2 and in presence of propane in dependence of pressure and temperature were investigated. The phase transitions of PE at atmospheric pressure were determined by differential scanning calorimetry (DSC). Furthermore, phase transitions of polymers under pressure of gases were measured by using an optical high pressure cell. Measurements of phase transition were performed in range of pressure of 1–90MPa. The results show that melting points of LDPE decreased in presence of CO2 and in presence of propane. For high-density polyethylene (HDPE) the melting point decrease was observed only in presence of propane, while in presence of CO2 melting point increases with increasing pressure. The melting points of LDPE and HDPE decrease in average for 10–20K in presence of propane, while in presence of CO2 the melting point decrease for both LDPE was lower (5–10K). Solubility and diffusivity of supercritical CO2 in two low-density polyethylenes (LDPE) and in high-density polyethylene (HDPE) were measured at temperature 373K and pressures up to 30MPa using a magnetic suspension balance (MSB). The solubility data were used for estimating the binary diffusion coefficients. The solubilities increased with increasing density. The diffusion coefficient shows strong CO2 density and CO2 solubility dependence. Diffusion coefficient starts to decrease with increasing density and solubility of CO2.
Alkyds are widely used polymers in the coating industry for decorative and industrial applications due to their low price, performance, diversity, and containment of renewable constituents. They have ...been of particular interest in research over the past decade owing to new legislative requirements focused on the reduction of volatile organic coatings (VOC) and the replacement of Cobalt (Co) driers. In the present work, the commercially accessible Fe (bispidon) drier and the Co (bis (2-ethylhexanoate)) drier were studied in high-solid (HS) alkyd coatings that are consistent with allowed VOC values as stipulated by actual EU legislation. Curing kinetic properties of the alkyd oxidation process were analyzed using FTIR spectroscopy. The influence of Fe and Co driers on crosslinking was further evaluated in terms of viscoelastic properties and surface hardness measurements. Finally, cured coating films were compared with the EIS method in order to determine the influence of driers on crosslinked polymer structures and pore resistance of HS alkyd coatings. We compared Fe and Co driers in HS long-oil alkyd coatings. Coatings with Fe drier showed comparable Final Drying Times but dissimilar crosslinking kinetic activity compared with the Co drier. Fe drier enable more uniformity through the entire thickness of the HS alkyd coating and consequently has lower diffusion of ions through the film.
Large amounts of Li ions can be electrochemically intercalated into and controllably released by the channels between individual molybdenum selenide nanotubes (see Figure), forming the basis for a ...promising safe new battery electrode material. The use of dichalcogenide nanotubes rather than the more usual carbon is shown to have important advantages.
The film formation process in waterborne (WB) epoxy coatings is studied using electrochemical impedance spectroscopy (EIS) measurements and dynamic mechanical analysis (DMA). Ten epoxy coatings with ...different pigment volume concentration were prepared on standard steel substrates and carefully monitored over four weeks (30 days). It is shown that impedance spectroscopy can serve as a very sensitive tool for accurate experimental detection of the critical pigment volume concentration. We also show that the optimal film formation process and corrosion stability of coatings are greatly affected by the coating pigment volume concentration (PVC) value. As a whole, the study confirms that the optimization of coating protection ability needs to take into account both maximization of the barrier effect as well as maximization of the degree of epoxy-amino cross-linking.
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