Abstract: The article is devoted to the investigation of the efficiency of chromium-modified montmorillonite dispersions to stabilize the collagen structure of the dermis. The interaction of modified dispersions of montmorillonite with collagen of the dermis was studied with the use of IR spectroscopic studies method. The high level of absorption of chromium compounds and their reduction by 30 % in the exhaust fluid was found. The use of montmorillonite dispersions provides qualitative formation of the structure of the dermis and physical and mechanical properties, with a reduction of tanning agents’ costs/waste by 16 %.
Abstract: The fire performance of a geocement-based binder was investigated with a combination of analytical techniques, in terms of changes in composition and microstructure. Geocement, formulated as Na2O∙Al2O3∙6SiO2∙20H2O, was prepared using metakaolin, sodium water-glass, rotten stone and sodium hydroxide. The mixture was homogenized by passing through a hydrodynamic cavitator. Cubes of 20 mm were prepared, hardened at laboratory conditions for 28 days, and subsequently burnt at 600, 800 and 1200 °C in a laboratory furnace. Cavitation treatment resulted in a highly amorphous binder; amorphous fraction decreased upon firing up to 800 °C due to crystallization, and increased above 1000 °C because of melt formation. Porosity increased with firing temperature and pores larger than 1 mm in diameter prevailed at 1200 °C. The material remained stable up to 1200 °C. The results indicate the adequacy of this geocement-based binder for preparing fire-protecting materials.
Abstract: To create the heat-bonded geotextile with desirable properties, the mix of fibres (hemp, recycled polyethylene terephthalate and polypropylene fibres) for nonwoven webs formation and additional polypropylene reinforcing mesh are used. The results of the study on the influence of the reinforcing mesh on the properties of nonwoven composites (NWCs) are presented. Mechanical properties, water penetration and air permeability of the thermoplastic mesh reinforced NWCs depend on the hemp fibre pre-treatment time, mass per unit area and thickness of the used web and location of the reinforcing mesh. Obtained results allow concluding that mechanical as well as water penetration characteristics of the produced heat-bonded geotextiles are higher, while air permeability is comparable to the properties of the commercial prototype.
Abstract: The aim of the study was to evaluate the surface energetic characteristics of wood-polymer composites (WPCs) based on recycled polypropylene (rPP) filled with ammoxidised lignocellulosic microparticles, obtained from aspen sawdust, a by-product of a Latvian company. The aspen sawdust, pre-hydrolysed in acidic medium, was treated with a reaction mixture of ammonium persulphate and NH4OH solution at their defined mass ratio during 120 h. The content of the introduced nitrogen was varied from 1,05 to 2,10%. It was found that the ammoxidation that was accompanied with the formation of amide linkages and the decrease of the hemicelluloses content enhanced the contact angles, decreased the work of adhesion and reduced the surface free energy of the WPC samples in comparison with the case of the composite filled with the initial sawdust. The valorisation of the wood particles increased their wettability towards the recycled polypropylene that had a positive effect on the WPC samples’ mechanical properties.
Abstract: One type of birch wood plywood by-product: plywood sanding dust (PSD) and recycled high density polyethylene (rHDPE) composites physical mechanical properties (tensile, flexural strength and modulus, impact strength and microhardness), water resistance and fluidity of the composite melts, were evaluated. These studies showed the possibility of the usage of presented by-product as an excellent reinforcement for recycled high density polyethylene matrix. It was observed that the modulus of the tensile for unmodified rHDPE+PSD composites increased up to 2.3 times, the modulus of flexural till 4 times, but the microhardness only 1.4 times. Optimal content of the PSD in recycled high density polyethylene composites could be 50 wt. %. As a coupling agent, the maleated polyethylene (MAPE) for modifying of the rHDPE+50 wt. % PSD composite was used. Due to the MAPE additives, the improvement (30-50 %) of the investigated exploitation properties was observed, but in comparison with unmodified composites the resistance of water increased up to 3.0 times. Optimal content of MAPE in rHDPE+50 wt. % PSD composition could be 3 wt.%.
Abstract: Cr3C2-Ni cermets exhibit high hardness and excellent corrosion, oxidation, abrasive and erosion resistance. However, nickel is toxic and carcinogen and because of that great efforts were made to displace or replace nickel in the composition of cermets. Therefore, in the present research chromium carbide-based cermets with FeCr-type ferritic binder was fabricated and investigated. Composites were sintered at different conditions: vacuum and spark plasma sintering. Spark plasma sintered cermets demonstrated acceptable structure and mechanical characteristics. Chemical composition of chromium carbide-based iron alloy bonded cermets was analyzed by energy-dispersive X-ray spectroscopy and structural analysis was carried out using X-ray diffraction. Sintered cermet consists of two main phases: α-Fe and (Cr,Fe)7C3 complex dicarbide. Mechanical characterizations – hardness and fracture toughness – was performed. Also oxidation rates were determined.
Abstract: In the present work, the neat epoxy and different orientations [0°, 45°, 90°, (45°/-45°/45°) s, (±45°/0°/90°) s] of unidirectional carbon/epoxy composites are experimentally studied under tensile and impact loading. The notched impact tests are performed using the Izod impact machine to obtain the energy absorption of neat epoxy and different CFRP composites which is required for effective design of bullet proof jackets and military vehicles. The micro mechanical analysis is employed to determine the shear properties of a matrix using the tensile properties. Using classical laminate theory [CLT], the theoretical tensile properties are determined. The SEM fractography analysis is used to observe the damage mechanisms of neat epoxy and different orientations of CFRP composites subjected to tension and impact loading.
Abstract: Zinc oxide nanoparticles doped with 0.2–1.5 mol% of Fe, Ni or Co and co-doped with 1 mol% of Ag were prepared by co-precipitation method and their photocatalytic activity in degradation of MB (methylene blue) water solution under ultraviolet irradiation was determined. X-ray diffraction analysis of the samples containing up to 0.5 mol% of iron group metals showed only ZnO and Ag phases. Crystallite size of doped ZnO nanoparticles was in the range of 27–31.6 nm depending on the sample composition and additional calcination at 400 °C. The photocatalytic activity of ZnO doped with iron group metals depended on the content of metals. The highest activity was observed for ZnO doped with 0.2 mol% of nickel. The co-doped with silver samples showed enhanced photocatalytic activity and higher reaction rate constant.
Abstract: In natural leather production polymeric compounds are generally used during leather finishing coating. However, given that liquid processing is crucial for derma structure and properties development, we have identified the rationale for applying polymers based on maleic and acrylic acids during chrome and titanium tanning of garment leather by analysing specimens of polymer-mineral tanning. We have applied analysis techniques traditional for leather industry (strength of surface, strength and percentage extension, shrinkage temperature, moisture content, mineral substances content etc.), as well as mathematical statistics techniques, in order to do it. It has been established that structure and custom properties development of polymer-mineral tanning leather products has been improved as compared with pickle-chrome tanning ones.
Abstract: In this study, the Interlaminar shear strength (ILSS) and flexural properties for five different laminate orientations [0°, 45°, [45°/-45°/45°]s, [±45°/0°/90°]s and 90°] of unidirectional carbon fiber reinforced plastic (CRP) and glass fiber reinforced plastic (GRP) composites are investigated. The different approach is used by applying the tensile load on notched specimens for measuring the inter-laminar shear strength. The theoretical flexural properties are obtained using the classical laminate theory [CLT]. The good agreement is obtained between the theoretical model and experimental results. The results indicate that the flexural strength and stiffness are higher for 0° laminate whereas flexural strain is higher for [45°/-45°/45°]s laminates as compared to other laminates. The scanning electron microscopy is used to observe the fracture surface of all laminate orientations of CRP and GRP composites.