http://hdl.handle.net/10563/1000003 2026-11-05T00:57:58Z http://hdl.handle.net/10563/1012867 A rheotens-based criterion for melt spinnability of virgin, recycled, petrol-based, and bio-based polymers Vilém, Rostislav; Kolařík, Roman; Fogašová, Mária; Plachý, Tomáš; Sedláček, Tomáš The development of a pragmatic laboratory criterion that can predict the spinnability of molten polymeric materials has the potential to reduce the necessity for costly industrial testing. The present study aims to compare the potential of existing conventional shear-based and extensional-based metrics with a proposed Rheotens-based metric in order to determine the most suitable method for material spinnability prediction. In this study, the characterization process encompassed virgin and reprocessed polyolefins (PE, PP), two PLA polymers (a spinning-grade polymer vs an extrusion grade), and two PLA/PHB blends (an industrially spinnable one vs an unspinnable one). So far, commonly used shear and classical extensional measurements incorporating the Beyreuther–Vogel criterion have been unsuccessful in differentiating between spinnable and unspinnable grades. We therefore refined the Rheotens test into a guided “impact” experiment at preset wheel speeds and defined a Rheotens Spinnability Index (RSI) from the force–take-up-speed curve. Within the present material set and experimental protocol, the RSI provided clear empirical decision ranges for the tested materials: RSI < 4 unspinnable, 4 ≤ RSI < 5 transition, and RSI ≥ 5 spinnable. The spinnability assignments were supported by melt-spinning trials on a Hills LBS-300 line, with additional verification of PLA and PLA/PHB materials on a ZDL-25 dry-melt line. Therefore, the proposed method offers a reference-free, single-material screening approach that outperforms shear-based metrics by directly probing extensional resistance and melt-strength build-up that influenced drawdown. The approach provides a practical tool for screening virgin, recycled, petrol-based, and biobased materials. 2026-01-01T00:00:00Z http://hdl.handle.net/10563/1012868 Utilization of waste plastic for plasma-assisted deposition of carbon nanowalls on electrodes for sustainable high-performance energy-storage devices Vesel, Alenka; Primc, Gregor; Mozetič, Miran; Tramšek, Melita; Gruden, Evelin; Fei, Haojie; Sáha, Petr; Lehocký, Marián; Zaplotnik, Rok Current global policies, such as circular economy, electrification, and low carbon footprint dictate the replacement of fossil fuels for synthesizing electrodes of graphene supercapacitors with renewable sources. The traditional method for depositing graphene and similar structures is based on gaseous hydrocarbons. The possibility of replacing them with waste plastic is presented. We used propane and waste plastics (mostly polypropylene) for the deposition of a few µm-thick deposit of carbon nanowalls composed of vertically oriented multilayer graphene-like sheets on electrodes by plasma-enhanced chemical vapor deposition (PECVD). We studied their morphology and structure, as well as the performance of coin-shaped supercapacitors. The graphene-like coatings were deposited in plasma sustained at the pressure of 16 Pa by inductively coupled RF discharge in the H mode at the forward power of 500 W and power density approximately 8x106 W/m3. Such a powerful plasma caused thermal decomposition of the waste plastic. Optical emission spectroscopy showed significant differences only within the first few seconds of plasma treatment, which was enough to supply precursors for graphene growth. Both scanning and transmission electron microscopies showed similar structures for deposits prepared from propane or waste plastic, and the deposition rates of roughly 100 nm/s were observed. Waste plastic enabled the deposition of 2–3 times densely packed multilayer graphene-like sheets of a typical thickness of 5 nm at deposition times over 1 min. Raman spectroscopy indicated a somewhat lower concentration of defects for samples deposited from polypropylene, but the ID/IG versus the average distance between the neighboring multilayer graphene-like sheets followed the same line. The specific capacitance increased steeply with deposition time for deposits prepared from waste plastic and it was found to be linearly dependent on the ratio between the effective and projected areas of both precursors. The capacitance versus the ID/IG followed the same curve for both precursors. The results demonstrate the feasibility of replacing gaseous hydrocarbons with waste plastics for PECVD deposition of graphene electrodes. 2026-01-01T00:00:00Z http://hdl.handle.net/10563/1012862 Progress in surface functionalized particle-based magnetorheological composites Munteanu, Andrei; Sedlačík, Michal In this chapter, we consider the effect of different types of coatings and shells on magnetic particles. By grafting different kinds of coating onto magnetic particles many typical difficulties for magnetic suspensions, such as corrosion and flocculation, can be overcome. The coating effect on three different systems magnetorheological fluids (MRFs), ferrofluids (FFs) and magnetorheological elastomers (MREs) is discussed in detail and different coatings are compared for each system. The coatings are further categorized based on applications with a few special cases, which are highlighted giving emphases to the applications and a comparison to uncoated particles. Lastly, the synthesis and grafting of coatings among coating characterization techniques are mentioned, followed by conclusions and some remaining problems which coatings and shells could potentially solve. 2023-01-01T00:00:00Z http://hdl.handle.net/10563/1012857 Insights into the impact of a green polar solvent on the properties of polysulfone membranes for gas separation applications Krchňáčková, Zuzana; Khellouf, Riyadh Abdekadir; Hanušová, Dominika; Šuly, Pavol; Münster, Lukáš; Dušánková, Miroslava; Plachý, Tomáš; Kovářová, Miroslava; Sedlařík, Vladimír Replacing toxic solvents with greener options in the preparation of polymer solutions and subsequent membranes is a matter of importance today. This study focused on the use of methyl 5-(dimethylamino)-2-methyl-5-oxopentanoate (MDMO) as an environmentally-friendly alternative to N-methylpyrrolidone (NMP) for the preparation of thin polysulfone films. The correlation between the thickness of the prepared membranes and the concentration and viscosity of the polymer solutions used was evaluated. Attention was also paid to the presence of residual solvents, which were investigated by Fourier-transform infrared spectroscopy, thermogravimetric analysis, headspace gas chromatography, and dynamic mechanical analysis. Gas permeation measurements were performed for three gases (CO2, N2 and O2) with different kinetic diameters of molecules. Although MDMO proved to be a good solvent for polysulfone, the tested cast films did not exhibit the same gas permeability as membranes prepared from polysulfone solutions based on N-methylpyrrolidone.