Mapové znaky na školních hospodářských mapách

Příspěvek byl podpořen v rámci projektu MUNI/A/1323/2022 Environmentální a socioekonomické změny v geografickém výzku

Effect of conditioning on PU foam matrix materials properties

This article deals with the characterization of the thermal-induced aging of soft polyurethane (PU) foams. There are studied thermal and mechanical properties by means of thermal analysis, tensile, compression and dynamic mechanical vibration testing. It was found in this study, that the increasing relative humidity of the surrounding atmosphere leads to the initiation of the degradation processes. This is reflected in the observed decreased mechanical stiffness. It is attributed to the plasticization of the PU foams wall material. It is in agreement with the observed increase of the permanent deformation accompanied simultaneously with the decrease of Young's modulus of elasticity. The latter phenomenon is studied by the novel non-destructive forced oscillations vibration-damping testing, which is confirmed by observed lower mechanical stiffness thus indicating the loss of the elasticity induced by samples conditioning. In parallel, observed decreasing of the matrix hardness is confirming the loss of elastic mechanical performance as well. The effect of conditioning leads to the significant loss of the PU foam's thermal stability.European Regional Development Fund in Research Centre of Advanced Mechatronic Systems project within Operational Programme Research, Development and Education [CZ.02.1.01/0.0/0.0/16_019/0000867]; Internal Grant of Palacky University in Olomouc [IGA_PrF_2021_031]CZ.02.1.01/0.0/0.0/16_019/0000867; Univerzita Palackého v Olomouci: IGA_PrF_2021_03

Study of the material engineering properties of high-density poly(ethylene)/perlite nanocomposite materials

This paper was focused on application of the perlite mineral as the filler for polymer nanocomposites in technical applications. A strong effect of the perlite nano-filler on high-density poly(ethylene) (HDPE) composites' mechanical and thermal properties was found. Also found was an increase of the Young's modulus of elasticity with the increasing filler concentration. Increased stiffness from the mechanical tensile testing was confirmed by the nondestructive vibrator testing as well. This was based on displacement transmissibility measurements by means of forced oscillation single-degree-of freedom method. Fracture toughness showed a decreasing trend with increasing perlite concentration, suggesting occurrence of the brittle fracture. Furthermore, ductile fracture processes were observed as well at higher filler concentrations by means of SEM analysis. There was also found relatively strong bonding between polymer chains and the filler particles by SEM imagining. © 2020 Lubomír Lapčík et al., published by De Gruyter 2020.European Regional Development Fund in the Research Centre of Advanced Mechatronic Systems project [CZ.02.1.01/0.0/0.0/16_019/0000867]; Palacky University in Olomouc [IGA_PrF_2020_022]; Faculty of Science, Palacky University in OlomoucCZ.02.1.01/0.0/0.0/16_019/0000867; Univerzita Palackého v Olomouci: IGA_PrF_2020_02

Materials characterization of advanced fillers for composites engineering applications

Four different minerals were investigated; hollow spheres of calcium carbonate, platy mica, needle like wollastonite and glassy perlite and characterized via iGC for surface energy, Freeman powder rheology for flow characterization, cyclic uniaxial die compaction for modulus of elasticity and frequency dependent sound absorption properties. Particle surface energy and particle shape strongly affected the packing density of powder beds. In the case of higher porosity and thus lower bulk density, the powders acoustic absorption was higher in comparison with higher packing density materials. Surface energy profiles and surface energy distributions revealed clear convergence with powder rheology data, where the character of the powder flow at defined consolidation stresses was mirroring either the high cohesion powders properties connected with the high surface energy or powder free flowing characteristics, as reflected in low cohesion of the powder matrix.Ministry of Industry and Trade of the Czech Republic [OP PIK CZ.01.1.02/0.0/0.0/16_084/0010256

Study of mechanical properties of epoxy/graphene and epoxy/halloysite nanocomposites

This article aimed to compare various mechanical properties of epoxy/graphene and epoxy/halloysite nanocomposites. Graphene nanoplatelets (GnPs) and halloysite nanotubes (HNTs) were used as fillers at different concentrations. The studied fillers were dispersed in the epoxy resin matrices. Elastic–plastic mechanical behavior modulation was observed utilizing the fillers’ nanoparticles and carboxyl-terminated butadiene–acrylonitrile copolymer rubber-modified epoxy resin. The hypothesis of the possible preceding inter-particle gliding of the individual GnPs in the complex resin nanocomposite matrix during mechanical testings was also confirmed. Increased ductility (elongation at break increased from 0.33 mm [neat matrix] to 0.46 mm [1 wt% GnPs] [39% increase]) and plasticity of the GnP nanocomposite samples were observed. In contrast, the decreasing mechanical stiffness as reflected in the decreased Young’s modulus of elasticity (from 3.4 to 2.7 GPa [20% decrease]) was found for the epoxy/HNT nanocomposites. The obtained dynamic stiffness of the investigated nanocomposites confirmed the complexity of the mechanical response of the studied material systems as a combination of the ductile and brittle phenomena.Web of Science121art. no. 2022052

Study of mechanical properties of epoxy/graphene and epoxy/halloysite nanocomposites

This article aimed to compare various mechanical properties of epoxy/graphene and epoxy/halloysite nanocomposites. Graphene nanoplatelets (GnPs) and halloysite nanotubes (HNTs) were used as fillers at different concentrations. The studied fillers were dispersed in the epoxy resin matrices. Elastic-plastic mechanical behavior modulation was observed utilizing the fillers' nanoparticles and carboxyl-terminated butadiene-acrylonitrile copolymer rubber-modified epoxy resin. The hypothesis of the possible preceding inter-particle gliding of the individual GnPs in the complex resin nanocomposite matrix during mechanical testings was also confirmed. Increased ductility (elongation at break increased from 0.33 mm [neat matrix] to 0.46 mm [1 wt% GnPs] [39% increase]) and plasticity of the GnP nanocomposite samples were observed. In contrast, the decreasing mechanical stiffness as reflected in the decreased Young's modulus of elasticity (from 3.4 to 2.7 GPa [20% decrease]) was found for the epoxy/HNT nanocomposites. The obtained dynamic stiffness of the investigated nanocomposites confirmed the complexity of the mechanical response of the studied material systems as a combination of the ductile and brittle phenomena.CZ.02.1.01/0.0/0.0/16_019/0000867; Tomas Bata University in Zlin, TBU: IGA/FT/2022/005, IGA/FT/2023/007; Univerzita Palackého v Olomouci: IGA_PrF_2022_020, IGA_PrF_2023_024European Regional Development Fund in the Research Centre of Advanced Mechatronic Systems project [CZ.02.1.01/0.0/0.0/16_019/0000867]; Palacky University in Olomouc [IGA_PrF_2022_020, IGA_PrF_2023_024]; Tomas Bata University in Zlin [IGA/FT/2022/005, IGA/FT/2023/007]; Fischer scholarship of the Faculty of Science, Palacky University in Olomou

Enhancement of the mechanical properties of HDPE mineral nanocomposites by filler particles modulation of the matrix plastic/elastic behavior

Two different nanosized mineral fillers (nano calcium carbonate and nanoclay) were used in the high density poly(ethylene) (HDPE) composites pilot plant production. Structural and mechanical properties of the prepared composites were examined in this study. The homogenous filler distribution was confirmed in the tested samples by scanning electron microscopy, transmission electron microscopy, and energy dispersive spectroscopy analyses. The fillers' fortifying effect on polymer composites' mechanical performance was confirmed as indicated by the increased elastic modulus and indentation modulus. Additionally, the possible modulation of the plastic-elastic mechanical behavior was confirmed by the type of the filler as well as its concentration used in the final composites testing articles.Palacky University in Olomouc [IGA_PrF_2021_031]; Tomas Bata University in Zlin [IGA/FT/2021/004, IGA/FT/2021/005]; Faculty of Science, Palacky University in OlomoucUniverzita Palackého v Olomouci: IGA_PrF_2021_031; Univerzita Tomáše Bati ve Zlíně: IGA/FT/2021/004, IGA/FT/2021/00

Acoustic and mechanical testing of commercial cocoa powders

In the present study, commercial cocoa powders with different cocoa fat contents were studied. It was found that the cocoa powders' flow patterns were of a cohesive to highly cohesive characters. It was demonstrated, that the powders of higher crystalline structure were less flowable compared to the ones with the more amorphous ones. It was observed by SEM that the studied cocoa powders of higher cocoa fat content and the ones with the dietary fibers content (sample 2) exhibited more amorphous structure. The predominantly smooth surface structure of the higher fat content cocoa powder allowed its higher dense packing, triggering the decreased sound absorption typical for non-porous materials as quantified by NRC of 0.289 (sample 1, 100 mm material height) and 0.227 (sample 3) to 0.182 (sample 2). The latter conclusions were also supported by the observed increase of the structural mechanical stiffness of the freely poured powder bed of high cocoa fat amorphous powders, as resulting in the increasing magnitude of the K-l of 12.83 MPa (sample 1, 100 mm material height) and 19.29 MPa (sample 3) to 37.82 MPa (sample 2). Melting temperatures of the samples were determined by DSC. Results were directly corresponded to the cocoa butter content. The highest enthalpy of fusion (Delta H (m)) of (23.32 +/- 0.21) J/g was obtained for the highest cocoa butter containing sample 2 (of 20-22 wt. %). Obtained values of Delta H (m) for samples 1 and 2 were of (12.38 +/- 0.20) J/g and (10.27 +/- 0.17) J/g. T-p (melt) for reversing heat flow was ranging from (30.16 +/- 0.10) degrees C to (32.28 +/- 0.10) degrees C indicating the melting of stable beta polymorph. The melting peaks observed at distinct temperatures in the non-reversing heat flow patterns were indicating melting of the unstable alpha and metastable beta' and stable beta cocoa butter polymorphic forms.Tomas Bata University in Zlin [IGA/FT/2022/005]; Palacky University Olomouc [IGA_PrF_2022_020]; Palacky University in Olomouc [IGA_ PrF_2022_020]Tomas Bata University in Zlin, TBU: IGA/FT/2022/005; Univerzita Palackého v Olomouci: IGA_PrF_2022_02

Metabolic engineering of novel lignin in biomass crops

Lignin, a phenolic polymer in the secondary wall, is the major cause of lignocellulosic biomass recalcitrance to efficient industrial processing. From an applications perspective, it is desirable that second-generation bioenergy crops have lignin that is readily degraded by chemical pretreatments but still fulfill its biological role in plants. Because plants can tolerate large variations in lignin composition, often without apparent adverse effects, substitution of some fraction of the traditional monolignols by alternative monomers through genetic engineering is a promising strategy to tailor lignin in bioenergy crops. However, successful engineering of lignin incorporating alternative monomers requires knowledge about phenolic metabolism in plants and about the coupling properties of these alternative monomers. Here, we review the current knowledge about lignin biosynthesis and the pathways towards the main phenolic classes. In addition, the minimal requirements are defined for molecules that, upon incorporation into the lignin polymer, make the latter more susceptible to biomass pretreatment. Numerous metabolites made by plants meet these requirements, and several have already been tested as monolignol substitutes in biomimetic systems. Finally, the status of detection and identification of compounds by phenolic profiling is discussed, as phenolic profiling serves in pathway elucidation and for the detection of incorporation of alternative lignin monomers

Aktualne aspekty dekarbonizacji w Czechach i możliwości zastąpienia węglowych źródeł energii odnawialnymi źródłami energii elektrycznej

The European Green Deal is a set of policy initiatives by the European Commission with the overarching aim of making Europe climate neutral in 2050. An impact assessed plan will also be presented to increase the European Union´s greenhouse gas emission reductions target for 2030 to at least 50% and towards 55% compared with 1990 levels. e European Green Deal has goals extending to many different sectors, including construction, biodiversity, energy, transport and food. For the European Union to reach their target of climate neutrality, one goal is to decarbonise their energy system by aiming to achieve net-zero greenhouse gas emissions by 2050. Article deals with current aspects of decarbonisation in the Czech Republic and possibilities of replacement coal energy sources by renewable sources of electric energy. Paper describes present situation in branch of production of electric energy and possible scenarios for reduction of coal energy sources in the Czech Republic.Europejski Zielony Ład to zestaw inicjatyw politycznych Komisji Europejskiej, których nadrzędnym celem jest uczynienie Europy neutralną dla klimatu w 2050 r. Przedstawiony zostanie również plan oceny wpływu, aby zwiększyć cel redukcji emisji gazów cieplarnianych w Unii Europejskiej do 2030 r. do co najmniej co najmniej 50% i około 55% w porównaniu z poziomami z 1990 roku. Europejski Zielony Ład ma cele obejmujące wiele różnych sektorów, w tym budownictwo, bioróżnorodność, energię, transport i żywność. Aby Unia Europejska osiągnęła swój cel neutralności klimatycznej, jednym z celów jest dekarbonizacja ich systemu energetycznego poprzez dążenie do osiągnięcia zerowej emisji gazów cieplarnianych netto do 2050 r. Artykuł dotyczy aktualnych aspektów dekarbonizacji w Czechach i możliwości zastąpienia energetyki węglowej źródła przez odnawialne źródła energii elektrycznej. Artykuł opisuje obecną sytuację w branży produkcji energii elektrycznej oraz możliwe scenariusze redukcji węglowych źródeł energii w Czechach