Comparison of the Flow of Permanent and Condensable Gases through an Asymmetric Porous Membrane

Porous inorganic membranes are usually composed of several layers, which are asymmetric with respect to the flow direction. For permanent gases, investigations about the influence of the flow direction on the mass flux through an asymmetric ceramic membrane were previously performed and can be found in literature. Mass flow differences between the two flow directions were calculated. Here the flow of condensable gases, i.e., of vapors, through the same membrane is analyzed and it is shown that the mass flow might be up to 40 % larger in one direction than in the other direction.     

Germanium-antimony-selenium-tellurium thin films: Clusters formation by laser ablation and comparison with clusters from mixtures of elements

Quaternary germanium-antimony-selenium-tellurium (Ge-Sb-Se-Te) thin films deposited from Ge_19.4Sb_16.7Se_63.9−xTe_x (x = 5, 10, 15, and 20) glass-ceramics targets by radio frequency magnetron sputtering were studied using laser ablation quadrupole ion trap time of flight mass spectrometry. Binary, ternary, and quaternary Ge_aSb_bSe_cTe_d clusters were formed and their stoichiometry was determined. By comparison of the clusters obtained from quaternary Ge-Sb-Se-Te thin films and those from ternary Ge-Sb-Te materials, we found that Ge-Te species are not detected from the quaternary system. Furthermore, Ge-Se and Se-Te species are missing in mass spectra generated from Ge-Sb-Se-Te thin films. From the Ge-Sb-Se-Te thin films, 16 clusters were detected while ternary Ge-Sb-Se glasses yielded 26 species. This might be considered as a signal of higher stability of Ge-Sb-Se-Te thin films which is increasing with a higher content of Te. The missing (Se₂⁺, Ge_aSb⁺ (a = 1–4), and GeSe_c⁺ (c = 1, 2)) and new (Ge⁺ and Sb_bTe⁺ (b = 1–3)) clusters may indicate that some of the structural features of the films (Ge₂Se_6/2 and Se₂Sb-SbSe₂) were replaced by (GeSe_4−xTe_x and SbSe_3−xTe_x) ones. In addition, when comparing the stoichiometry of clusters formed from Ge-Sb-Se-Te thin films with those from the mixtures of the elements, only Sb₃⁺ and SbSe⁺ were observed in both cases. The knowledge gained concerning clusters stoichiometry contributes to the elucidation of the processes proceeding during plasma formation used for the chalcogenide thin films deposition.     

Windshield recycling focused on effective separation of PVB sheet

The study is focused on windshield recycling process resulting in poly(vinyl butyral) (PVB) sheets with very low amout of remain glass particles. PVB sheets were obtained from worldwide manufacturer DuPont and then they were laminated by standard autoclaving process. One sample of PVB sheet was modified by multi‐functional organic acid in order to compare various levels of adhesion. Three‐stage technology was proposed for recycling PVB sheets. In the first‐stage laminated safety glass was mechanically cracked. In the second‐stage the adhesion reduction to minimal degree was followed by chemical‐physical assisted separation. It causes self‐release of the glass out of the PVB sheet. The third‐stage was mechanical peeling of the remaining glass from the PVB sheet which completed the recycling process. The optimal process conditions for the most effective delamination process were found. Delamination technology produces PVB sheet with minimal residual glass content (up to 300 ppm) and minimal change in PVB sheet properties. Described recycling technology is ecologically friendly (the effluent is fully recyclable as well) and could reduce the worldwide problem with windshield waste disposal. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39879.     

Preparation of CaCO3‐based biomineralized polyvinylpyrrolidone–carboxymethylcellulose hydrogels and their viscoelastic behavior

In the blend of natural and synthetic polymer‐based biomaterial of polyvinylpyrrolidone (PVP) and carboxymethylcellulose (CMC), fabrication of CaCO₃ was successfully accomplished using simple liquid diffusion technique. The present study emphasizes the biomimetic mineralization in PVP–CMC hydrogel, and furthermore, several properties of this regenerated and functionalized hydrogel membranes were investigated. The physical properties were studied and confirmed the presence of CaCO₃ mineral in hydrogel by Fourier transform infrared spectroscopy and Scanning electron microscopy. Moreover, the absorptivity of water and mineral by PVP–CMC hydrogel was studied to determine its absorption capacity. Further, the viscoelastic properties (storage modulus, loss modulus, and complex viscosity) of mineralized and swelled samples (time: 5–150 min) were measured against angular frequency. It is interesting to know the increase of elastic nature of mineralized hydrogel filled with CaCO₃ maintaining the correlation between elastic property and viscous one of pure hydrogel. All these properties of biomineralized hydrogel suggest its application in biomedical field, like bone treatment, bone tissue regeneration, dental plaque and tissue replacement, etc. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40237.     

Analysis of polymer viscoelastic properties based on compressive creep tests during hot embossing for two‐dimensional polyethylene terephthalate nanochannels

Hot embossing is an emerging technology, which enables cost‐effective and high‐productivity nanofabrication. It is important to optimize the processing parameters to achieve high replication accuracy nanostructure fabrication. In this article, to reveal the interrelationship between the hot embossing conditions and replication accuracy of two‐dimensional (2D) polyethylene terephthalate (PET) nanochannels, the numerical simulations were conducted by using the generalized Maxwell model. The constants of the generalized Maxwell model were calculated by a newly established fitting formula based on experimental compressive creep curves rather than tensile stress relaxation curves. Replication accuracy of 2D PET nanochannels was evaluated by a method based on weighted averages. Orthogonal method was employed during numerical simulations to optimize the hot embossing process. Under optimized hot embossing parameters, 2D PET nanochannels, ～80 nm wide, 250 nm deep and 4 mm long, were precision‐imprinted into a PET sheet. POLYM. ENG. SCI., 54:2398–2406, 2014. © 2013 Society of Plastics Engineers     

Studies on γradiation treatment of poly(tetrafluoroethylene) powder

γ-Irradiation of poly(tetrafluoroethylene) (PTFE) in the presence of air results in degradation of polymer chains by insertion of oxygen. At first, in the low-dose range below 400 kGy, a rise in crystallinity can be observed due to main chain scission in the amorphous part of the macromolecules. Dose increase up to approximately 1000 kGy causes progressive degradation of molecular weight as well as a growing degree of carboxylation of PTFE and increased concentration of trifluoromethyl groups in near-surface regions. At constant irradiation temperature, the properties of irradiated PTFE hardly depend on dose rate and starting material. The degree of carboxylation of the irradiated unsintered PTFE is appreciably lower in comparison with electron-irradiated PTFE under comparable conditions. © 1996 John Wiley & Sons, Inc.     

Solubility of potassium ferrate in 12 M alkaline solutions between 20°C and 60°C

The solubility of potassium ferrate (K₂FeO₄) was measured in aqueous solutions of NaOH and KOH of total concentration 12 M containing various molar ratios of KOH:NaOH in the range 12:0 to 3:9. Several analytical methods were tested for the determination of ferrate concentration. The final method chosen consisted of potentiometric titration of the ferrate sample with an alkaline solution of As₂O₃. The assumption was made that ferrate dissociates in concentrated KOH solutions predominantly to KFeO₄⁻. The solubility constant, S, defined as the product of the molar concentration of the potassium ion, K⁺, and the ferrate anion, KFeO₄⁻, was found to be 0·044 ± 0·006 mol² dm⁻⁶ for 20°C, 0·093 ± 0·004 mol² dm⁻⁶ for 40°C and 0·15 ± 0·09 mol² dm⁻⁶ for 60°C. From these results the heat of dissolution of K₂FeO₄ was calculated as −14·3 kJ mol⁻¹. At 60°C the enhanced decomposition of the ferrate at the higher temperature led to a greater deviation in solubility values compared with data for either 20°C or 40°C.     

Influence of Electron Beam Irradiation on High‐Temperature Mechanical Properties of Ethylene Vinyl Acetate/Carbon Fibers Composites

The purpose of this study was to investigate the effect of carbon fiber (CF) and electron‐beam (EB) radiation on high‐temperature mechanical properties of ethylene‐vinyl acetate (EVA). Polymer composites were prepared by mixing on a two‐roll mill. After compression molding, the samples were irradiated between 60 and 180 kGy, and dynamic mechanical analysis (DMA) was used to characterize physical properties. The effects of filler content and radiation level on the mechanical properties of EVA/CF were evaluated. The shear stress and modulus were observed to increase with increasing of the filler level. However, there was a dramatic decrease in creep compliance. It was also shown that introduction of irradiation on EVA composite increases the shear stress and the real part of the dynamic shear modulus G' due to the increase in molecular weight and cross‐linking of the polymer after irradiation. J. VINYL ADDIT. TECHNOL., 26:325–335, 2020. © 2019 Society of Plastics Engineers     

Determination of green,blue and yellow artificial food colorants and their abuse in herb-coloured green Easter beers on tap

Beer is one of the most popular alcoholic beverages worldwide. For consumer acceptance, significant factors are its taste, flavour and colour. This study determines selected synthetic green, blue and yellow food colorants in popular Easter herb-coloured green beers on tap produced in breweries on Holy Thursday. The abuse of beer colouring with Tartrazine (E 102), Quinoline yellow (E 104), Sunset yellow (E 110), Patent blue (E 131), Indigo carmine (E 132), Brilliant blue FCF (E 133), Green S (E 142) and Fast green FCF (E 143) was assessed in 11 green beer samples purchased in local restaurants. HPLC was used for the separation and detection of artificial colorants with diode-array detection and a Chromolith Performance CN 100 × 4.6 mm column with guard pre-column Chromolith CN 5 × 4.6 mm. Separation was performed in gradient elution with mobile phase containing methanol–aqueous 2% ammonium acetate at pH 7.0. The study showed that eight beers (70%) marketed in the Czech Republic contained artificial colorants (Tartrazine and Brilliant blue FCF). The concentration of colorants found in analysed green herb-coloured beers ranged from 1.58 to 3.49 mg l^–1 for Tartrazine, 0.45–2.18 mg l^–1 for Brilliant blue, while Indigo carmine was detected only once at concentration 2.36 mg l^–1. Only three beers showed no addition of the synthetic colorants. However, the levels of artificial colorants found in beers marketed in the Czech region were very low and did not show a serious risk for consumers’ health.     

Preparation of dehydroxylated and delaminated talc: Meta-talc

The roentgen-amorphous delaminated and dehydroxylated phase was prepared applying intensive milling procedure and subsequent thermal treatment of talc. Due to the similarity in properties and in thermal behavior of this material with roentgen-amorphous delaminated and dehydroxylated kaolinite phase, i.e. meta-kaolinite, the name meta-talc was suggested for this material. The properties and the behavior during thermal treatment were investigated using thermal analysis, x-ray diffraction analysis, infrared spectroscopy and scanning electron microscopy. The suggested procedure changes the activation energy of dehydroxylation, the behavior during thermal treatment and the phase composition of the product. The kinetics and thermodynamics of the thermal transition were evaluated using Kissinger equation and Eyering law.