The use of polymer thin films is currently implemented in almost every aspect of modern life due to their cost-efficiency, lightness, flexibility, and unique physical and chemical properties. The ...reason for focusing research into polymer thin films is to understand their thermodynamic and kinetic mechanisms, such as interfacial interactions, flow behavior, film formation, relationships between deposition process parameters and the film structure, and other advanced functional properties. Thin polymer film research focuses on a wide range of industrial applications, including energy technologies, optics, sensors, microelectronics, medicine, biotechnology, etc. This Special Issue highlights and discusses studies on the formation of polymer films, their morphological analysis, and their use in various applications, including sensors, antifouling coatings, and coatings for harnessing solar energy. In addition, this Special Issue also includes two review papers on the latest research on polymer-waveguide-based optical sensors and the integration of antifouling and anti-cavitation coatings on propellers.
To decrease the amount of plastic waste, the use of recycling techniques become a necessity. However, numerous recycling cycles result in the mechanical, thermal, and chemical degradation of the ...polymer, which leads to an inefficient use of recycled polymers for the production of plastic products. In this study, the effects of recycling and the improvement of polymer performance with the incorporation of an additive into recycled polypropylene was studied by spectroscopic, rheological, optical, and mechanical characterization techniques. The results showed that after 20 recycling steps of mechanical processing of polypropylene, the main degradation processes of polypropylene are chain scission of polymer chains and oxidation, which can be improved by the addition of a stabilizing additive. It was shown that a small amount of an additive significantly improves the properties of the recycled polypropylene up to the 20th reprocessing cycle. The use of an additive improves the rheological properties of the recycled melt, surface properties, and time-dependent mechanical properties of solid polypropylene since it was shown that the additive acts as a hardener and additionally crosslinks the recycled polymer chains.
The physical properties as well as thermal and electrical stability of copper particles can be improved by surface protection, which mainly depends on the coating material. Our study was, therefore, ...focused on the rheological, thermal, mechanical and electrical characterization of polymer composites by comparing uncoated (Cu), silver-coated (Cu@Ag) and silica-coated (Cu@Si) copper flakes in low-density polyethylene at various volume concentrations (up to 40%). Interactions among particles were investigated by rheological properties, as these indicate network formation (geometrical entanglement), which is important for mechanical reinforcement as well as establishing an electric pathway (electrical percolation). The results showed that geometrical and electrical percolation were the same for Cu and Cu@Si, ~15%, while, surprisingly, Cu@Ag exhibited much lower percolation, ~7.5%, indicating the fusion of the Ag coating material, which also decreased crystal growth (degree of crystallinity). Furthermore, the magnitude of the rheological and mechanical response remained the same for all investigated materials, indicating that the coating materials do not provide any load transfer capabilities. However, they profoundly affect electron transfer, in that, Cu@Ag exhibited superior conductivity (74.4 S/m) compared to Cu (1.7 × 10−4 S/m) and Cu@Si (1.5 × 10−10 S/m). The results obtained are important for the design of advanced polymer composites for various applications, particularly in electronics where enhanced electrical conductivity is desired.
Two types of innovative coatings based on fluoroethylene/vinylether alternating copolymers are investigated as protective systems for bronze works-of-art. The influence of a polyhedral oligomeric ...silsesquioxane (POSS), i.e. open-cube trisilanol-heptaisooctyl-POSS, on the surface, mechanical, optical and electrochemical properties of coatings is examined. It is found that the isooctyl groups in the organic shell of POSS cause an increase in the hydrophobicity of the surface. On the other hand, nanoindentation tests show that the reduced modulus, hardness and plasticity index decrease with the addition of POSS, while abrasion resistance is slightly improved. Haze of coatings increases when POSS nanoparticles are present. More importantly, a beneficial effect of POSS addition on the protective efficiency against corrosion is assessed by exposure of coatings to acidic vapours and electrochemical treatments. In this regard, potentiodynamic polarisation clearly shows that the protective efficiency is systematically larger for coatings comprising POSS. The ex situ IR reflection-absorption spectroelectrochemistry shows that cuprous oxide can eventually form at the coating|bronze interface, which is identified through the spectroelectrochemistry of unprotected bronze.
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•Combination of protective efficiency and removability in anticorrosion coatings suitable for conservation of bronze.•Homogeneous distribution of POSS nanoparticles in fluoroethylene/vinylether-based coatings.•Cuprous oxide may form at the bronze|coating interface at high anodic potentials.•POSS nanoparticles addition enhanced hydrophobicity and protective efficiency while decreasing mechanical properties.
Since the world’s energy demands are growing rapidly, there is a constant need for new energy systems. One of the cleanest, most abundant, and renewable natural resources available is solar energy; ...therefore, the development of surfaces with high absorption of solar radiation is increasing. To achieve the best efficiency, such surfaces are coated with spectrally selective coatings, which are strongly influenced by the pigments and resin binders. Spectrally selective paints have a very specific formulation, and since the applied dry coatings should exhibit high spectral selectivity, i.e., high solar absorptivity and low thermal emissivity, the rheological properties of liquid paints are of great importance. In the present work, we studied the effect of the rheological properties of liquid thickness-insensitive spectrally selective (TISS) paints on the spectral selectivity and adhesion of dry coatings on a polymeric substrate. The results showed that the functional and adhesion properties of dry coating on polymeric substrates is strongly dependent on the rheological properties of the binder and catalyst used for the preparation of the liquid paints. It was shown that the paints with good spectral selective properties (thermal emissivity eT < 0.36 and solar absorptivity aS > 0.92) and good adhesion (5B) can be prepared for polymer substrates.
The number of commercial products claiming self-cleaning properties is rising and testing of long-term activity and durability of such coatings needs to be addressed more. The time-dependent changes ...of different characteristics like haze, transparency, and color are essential for transparent glazing materials. Herein, we aimed to examine whether the laboratory results obtained on the Zr-modified-titania-silica (TiZr) self-cleaning materials would translate to larger-scale outdoor-exposed testing. TiZr thin films were deposited via spraying onto float glass window surfaces and exposed into three different environments for 20 months. For comparison, a commercially available active SGG BIOCLEANTM glass and standard float glass were simultaneously exposed in the same conditions. It was shown that the self-cleaning property of either a commercial product or TiZr-coated float glass was not considerably effective in real field test conditions, although the previous laboratory tests showed pronounced photocatalytic activity of TiZr thin films. The inclination angle; however, was shown to have a considerable effect on the self-cleaning ability of samples, as did the rain patterns during the testing period. On the other hand, the anti-fogging effect of our TiZr material was very well expressed in controlled laboratory conditions (measuring droplet formation time) as well as in the real outdoor environment.
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Relatively low viscosity with poor resolution and shape fidelity make soft gelatine hydrogel still challenging to use as an ink or bio-ink for 3D printing, despite its good ...shear-thinning behaviour and high potential in tissue engineering due to its biocompatibility and similarities to biological tissues. A horizontally-induced cooling platform has thus been proposed to accelerate the physical stabilisation of each printed deposit during such a multilayer printing by fastening its phase-change (gelation) transition, which would affect its flow (shear-thinning) and gel strength (viscoelasticity), and thus enable scaffolds to be created with more precise porosities and geometries.
In order to verify the physical properties (sol-gel transitions, gelation point, gel strength) and the kinetics of gelatine solutions (5 and 10 wt%) during such printing conditions, the viscosity and oscillatory rheology as a function of kinetically different cooling / heating rates (5−48 °C/min) have been performed in the range from 37 to 0 vs. -30 °C.
The gelation of 10 wt% gelatine was shown to decrease by 4 °C (to 18 °C) when the plate was cooled to 0 °C, and the cooling speed rate was changed from 5 to 42 °C/min, which increased its complex viscosity (η*) for 485 Pa (to 1135 Pa) by forming tight and in a flow direction-oriented clusters of multi/triple-helices, being confirmed with FTIR spectroscopy. The lower plate temperature (-30 °C) didn't change solutions' gelation transition significantly, while it only increased the η* (from 43 to 470 Pa) of 5 wt% hydrogels at lower cooling speed (5−12 °C/min) by forming larger and more disordered aggregates, getting immobilised by fast crystallisation of the aqueous medium.
It can be concluded that, besides the gelatine concentration, the cooling speed has a major impact on its physical stabilisation by yielding macromolecularly differently structured gels, which shall affect the printability, as well as give different porous structures.
A novel Thickness Sensitive Spectrally Selective (TSSS PU B:
a
s=0.90,
e
T=0.20) paint coating on aluminium substrate was prepared from commercially available polyurethane binder (Binder B) (HELIOS ...TBLUS, SI) and black pigment (spinel (Mn–Fe)), in combination with trisilanol polyhedral oligomeric silsesquioxane (POSS), which served as pigment dispersant. Polyurethane resin binder B was selected because of its higher thermal stability (determined from thermogravimetric measurements (TG)) than polyurethane resin binder A, which has previously been used for making Thickness Insensitive Spectrally Selective (TISS PU A) coatings (
a
s=0.90,
e
T=0.38) deposited on copper absorbers (Kunič, 2009
36).
Thermal degradation of the TSSS PU B and TISS PU A coatings, both deposited on aluminium substrates, was studied by following, as close as possible, the methodology worked out within TASK 10 of the IEA's Solar and Heating Programme. Thermal load tests were performed in the temperature range from 170 to 200
°C at various time intervals (1, 6, 10, 15, 21 days). Degradation of the coatings was assessed using a variety of degradation indicators: changes of solar absorptance and thermal emittance determined from the hemispherical IR and VIS/NIR spectra, intensity changes of selected vibrational modes attributed to the polymeric backbone and ester and urethane linkages and combined with peel-off tests used as adhesion and cohesion indicators. The results revealed that degradation of the polyurethane resin binder was attributable to the breaking of the urethane linkages, also shown from the AFM and XPS spectra measurements. For the TISS PU A coating, the life expectancy was estimated to be
22.77 years (activation energy (
E
a)=163.2
kJ/mol,
T
eff=113.4
°C) while for the TSSS PU B coatings, it was at least
25.96 years (activation energy (
E
a)=96
kJ/mol,
T
eff=102
°C).
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► Polyhedral silsesquioxane (POSS) was used as dispersant for making solar paints. ► Spectrally selective paint coatings were deposited on Al substrates. ► Degradation of coatings was investigated from the infrared spectra of coatings. ► Lifetime of coatings was obtained from activation energies and Arrhenius plots. ► Surface morphology changes of coatings were assessed from the XPS spectra.
Manufacturing of flexible electrochromic (EC) devices requires the use of low-temperature films for deposition on electronically conductive foils. With this aim, low-temperature V-oxide films were ...spin-coated from a dispersion prepared by milling of crystalline V2O5 powder in vanadium(V) tri-n-propoxide oxide/isopropanol sol as dispersant. TEM images showed that the milling procedure enables the introduction of some V2O5 nanocrystallites into the matrix of the V-oxide pigmented film prepared at 150 °C. The electrochromic properties were analyzed using in situ UV–visible absorbance spectroelectrochemistry. The low transmittance values of as-prepared pigmented films revealed the presence of a greater amount of reduced V4+ centers compared to the crystalline sol-gel V2O5 model films. Significant bleaching of pigmented V-oxide films occurred during subsequent 521 cycles in the safe potential range.
Three different types of vibrational spectroscopies were applied to examine the powdered V-oxide film, and the results were compared to the band changes for the sol-gel crystalline V2O5 films. For initial films, the modes in the IR reflection-absorption spectra were systematically shifted to higher wavenumbers with regard to the modes in the IR absorbance spectra. Both IR techniques confirmed the reversible shift of the vanadyl V-OA band to lower frequencies and the disappearance of the bridging V-OB-V mode upon intercalation. Raman spectra showed the appearance of two vanadyl stretching modes at 986 and 961 cm−1 that occurred simultaneously with the decrease in the intensity of the bands in the 750–400 cm−1 spectral region. After the deintercalation, the Raman spectra of the low-temperature films showed broad bands that remained after the second bleaching. Finally, a flexible NiO1-x/ormolyte/V-oxide EC device was constructed. The device was composed of two different pigmented films and demonstrated the practical applicability of the low-temperature pigmented films.
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•Low-temperature pigmented V-oxide films with nanocrystalites of V2O5 were fabricated.•V4+ was also present in V-oxide films that were bleached during the cycling.•Ex situ IR reflection-absorption, IR absorption and Raman spectroscopy were applied.•Vibrational properties of pigmented V-oxide were compared to those of crystalline V2O5.•A flexible Ni1-xO/ormolyte/V-oxide EC device was fabricated using two types of pigmented films.
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•Solvent-born polyurethane-based protective coatings for bronze were developed.•Influence of POSS on mechanical properties and protection efficiency was studied.•Hardness, elastic ...modulus were not influenced, but abrasion resistance was improved.•Ex situ IR RA confirmed the benevolent influence of POSS on protection efficiency.•Dielectric constants and coating resistivities reflect positive influence of POSS.
Two-component solvent-born polyurethane coatings for the protection of bronze from corrosion were prepared. Trisilanol-heptaisooctyl polyhedral oligomeric silsesquixane (POSS) nanoparticles were exploited to increase the coating protective efficiency. Its improvement was confirmed through a combination of characterisation techniques. In particular, the POSS addition caused an increase of the water contact angle, and an enhancement of the elastic connotation and abrasion resistance of the polyurethane coating. Potentiodynamic polarisation measurements also indicated that the coating containing POSS nanoparticles has an improved protection efficiency. Impedance spectroscopy revealed that the magnitude of low-frequency impedance of polyurethane coatings decreased more for the coating without POSS during exposure in electrolyte for thirty days. Ex situ IR reflection-absorption spectroelectrochemistry was exploited to get insight into the degradation of coatings during chronocoulometric charging at anodic potentials. IR reflection-absorption technique was also used to evaluate any possible effect of different stripper solutions on the bronze substrate.
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