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Polymer resins based on acrylates obtained from Bis-GMA (Bisphenol A glycide methacrylate), which is suitable for photopolymerization, are used in dentistry for various purposes due to the ease of application and the possibility to influence their properties by adding reinforcements of different shapes, crystal structure and chemical compositions. Reinforcement in the form of particles based on MgAlLDH (layered double hydroxide) deposited on silica obtained from rice husks on two substrates. A metal base and glass were used. The adhesive properties are important in order to see the possibility of using these materials in applications. In order to measure the adhesive properties of the material, the composite microhardness measurement method is used by applying different loads in order to evaluate the adhesion parameter that shows the effect of the coating on the substrate. It was compared to how a pure photopolymerizing acrylate matrix bonds with a chromium-based dental alloy substrate that is used in the production of different parts of dentures by bonding to a glass substrate. Then, it was compared how composite materials are bonded to both substrates. Adhesion was monitored through the change in wetting angle between the composites, and the results were compared with the results of microindentation. It was shown that the addition of composite particles increases the adhesive properties of the composite compared to the pure matrix and that better adhesion is achieved between the composite and the metal substrate than between the composite and the glass substrate.

The paper shows the possibilities of increasing the hydrophobicity of the paper surface by applying layers of hydrophobic material to the surface. Various application techniques and the following substances were tested: stearic acid, shellac and zinc-hydroxide. Hydrophobicity was tested using the modified Cobb method, measuring the contact angle and drop retention time. The presence of hydrophobizing agents was confirmed by FTIR spectroscopy. It was found that the methods of applying the hydrophobizing agent, used in this work, give much better results with stearic acid, compared to shellac. This manuscript presents novel possibilities of increasing paper surface hydrophobicity by applying layers of hydrophobic material to the surface. Various layer application techniques were examined, as well as substances including: stearic acid, shellac and zinc-hydroxide. Hydrophobicity was tested using the modified Cobb method, measuring the contact angle and drop retention time. The presence of hydrophobizing agents was confirmed by FTIR spectroscopy. Based on the results achieved, it can be concluded that the methods of applying the hydrophobizing agent, used in this work, give much better results with stearic acid, compared to shellac.

Rice husk was used to produce silica particles, which were then used to reinforce the polymer matrix. The synthesized SiO2 particles were characterized using X-ray diffraction, Fourier transforms infrared spectroscopy (FTIR) and scanning electron microscopy with EDS. In a PMMA matrix, prepared SiO2 particles in amounts of 1, 3, and 5 wt.% were used as reinforcing agents. The goal of this research was to see if SiO2 particles had any effect on the mechanical properties of polymer composite materials. The morphology of the composites was examined using a field emission scanning electron microscope (FE-SEM). Vickers microindentation hardness and impact testing were used to determine the mechanical properties of the obtained composites. The indentation creep’s behavior of a polymethylmetacrylate (PMMA) composite material with varying amounts of nanoparticles (SiO2) was investigated and analyzed.

The subject of this study is the synthesis of glycolysates from recycled poly (ethylene terephthalate) (PET) by depolymerization using diethylene glycol (DEG) in the presence of catalyst FASCAT 4100. The resulting glycolysate was then treated with maleic anhydride and finally with 2-octanol to obtain a 2-EtHex/MA/DEG/PET/EG/MA/2-EtHex plasticizer. The characterization of the obtained plasticizer was performed by infrared spectroscopy with Fourier transform (FTIR) and NMR spectroscopy. The obtained plasticizers were mixed into bitumen with 10 wt. % and tests of mechanical properties of obtained products were performed.

Adsorption of anthraquinone dye Acid Blue 111 by alumina-iron oxide doped particles prepared by sol-gel method from aqueous solutions was studied. The adsorbent morphology was revealed by FESEM and the crystallographic phase is analyzed by the XRD technique. The effect of adsorbate and adsorbent concentrations, pH value, type of adsorbent and thermodynamic parameters on dye removal by adsorption was studied. The change of dye concentration during the adsorbtion was followed using the UV-Visible spectrophotometer. The change of the adsorbent surface before and after dye removal was observed using the Fourier Transformation-infrared spectroscopy (FT-IR). The adsorption kinetics is in accordance with the pseudo-second-order kinetics model. The Langmuir and Freundlich adsorption isotherm models were used to describe the adsorption process. The thermodynamic study of dye adsorption proves the process is spontaneous with exothermic nature.

Thermal properties of acrylate-based composite combined with alumina-based particles were investigated. The composites were made of poly (methyl methacrylate) (PMMA) modified with dimethyl itaconate (DMI) as a matrix. Neat alumina particles (Al2O3) and alumina doped with iron oxide (Al2O3-Fe) modified with 3-aminopropyl-trimethoxylane (AM) and flax oil fatty acid methyl esters (biodiesel - BD) were used as reinforcement. Thermal conductivity measurements showed that composite with alumina particles with the highest alpha phase content had the highest thermal conductivity values. Mechanical properties (tensile strength, modulus of elasticity and elongation at break) were improved by the addition of modified alumina particles to PMMA/DMI matrix. The thermal properties are the most improved for composite with 3 wt.% Al2O3-Fe-AM particles that had the lowest temperature in a crack zone was noticed (10.28 %) compared to PMMA added due to the better stiffness and highest thermal conductivity.

Composite materials based on acrylate UV-cured polymers (Bis-GMA/TEGDMA) as a matrix and reinforcements that can be selected in order to adjust the properties of the obtained composite are used in the field of dental technology. The role of reinforcement is to adjust the mechanical properties, but also to control the shrinkage during curing. As reinforcement, alumina particles doped with iron oxide (Al2O3 Fe) synthesized using the sol-gel technique were selected. In order to simulate the process of adhesive application in real conditions, in vitro testing technique and adhesion properties of synthesized adhesive were used, where tooth tissue was used as a substrate. Comparison with standard adhesives used in dentistry was used to compare adhesion. The quality of the adhesive joint was evaluated using the microhardness testing method using different loads where it is estimated how the adhesive makes a connection with the substrate. It was shown that the synthesized adhesive showed significantly enhanced adhesion compared to the standard adhesive used in dentistry (836%).

Basalt as a filler in a polymer-based composite material fulfils the demand of being natural, environment-friendly material for the production of various composite materials. The material could be used as protective layer and the abrasion should be tested in order to evaluate the properties of the material. The cavitation test enables the evaluation of the possible service in conditions that simulate the extensive erosion. The presence of basalt in the matrix improves the resistance to cavitation. The possibility to further improve the material could be obtained using the reinforcement of the matrix itself by incorporation of submicron ceramic particles into the composite. The obtained hybrid composite material with the addition of reinforcement in the matrix further improves the cavitation resistance. [Projects of the Serbian Ministry of Education, Science and Technological Development, Grant no. TR34011 and Grant no. OI 176016]

Two-step synthesis of Fe2O3 particles, performed by precipitation from iron(III) chloride (FeCl3•6H2O) using ammonium hydroxide in first step and calcination at 400 and 700°C during 4 h, provided Fe2O3 400°C and Fe2O3 700°C photocatalysts, respectively. The electrospinning process was used to prepare iron oxide fibers, named Fe2O3 fiber. Morphological and structural properties of samples were determined by Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Fourier Transform Infra-Red (FT-IR) and BET/BJH analysis. It was found that the α-Fe2O3 phase (hematite) has shown the compaction of the structure at 700°C, i.e. lower textural properties. Hematite particles and fibers are used for bisphenol A (BPA) removal by photocatalytic decomposition and the enhanced catalytic performance was found with the use of Fe2O3 400°C particles. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. TR34011]

This study presents preparation and characterization of ethyl cellulose based nanocomposites. Successful use of simple solvent casting technique provided nanocomposites with high loads of barium ferrite magnetic nanopowder in the polymer matrix, promising significant improvement of mechanical properties. Investigation of morphology revealed formation of agglomerates that are still on nanoscopic level. Nanocomposite thin films with a higher content of the magnetic powder showed substantial enhancement of break strength, elongation and microhardness compared to the pure ethyl cellulose, which was the primary aim of this research. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. TR34011, Grant no. III 45019 and Grant no. ON172037]

Hybrid composite panels of Wood-Plastic Composites (WPC) consisting of wood and poly (methyl methacrylate) (PMMA) were reinforced with alumina particles and made by “hot pressing” method. Alumina-based particles were made by sol-gel technique. The particles were characterized by the X-ray diffraction (XRD). The resulting alumina particles were modified with (3mercaptopropyl) trimethoxysilane (MPTMS), in order to obtain better mechanical properties of the composite relative to the composite with unmodified alumina particles. The aim of this work was to study the influence of composite structure and the moisture absorption on bending and the impact properties of the hybrid composite. The bending and impact tests revealed that modulus of elasticity and absorbed energy of deformation increased with modification of alumina and slightly decrease after moisture absorption. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. TR34011]

Composite materials based on UV-curing acrylates and various alumina-based reinforcements represent material that is suitable for the use in dentistry, but also in other areas. Composites were made using four different types of reinforcement of chemically very similar compositions, but different size and morphologies. In order to monitor the mechanical properties of the composite material, samples were made in the form of discs of defined dimensions suitable for polymerization under UV light. The subject of this study is the examination of the mechanical properties of the Bis-GMA (Bisphenol A glycidyl methacrylate)/TEGDMA (trimethylene glycol dimethacrylate) photopolymer composite material as a matrix. The reinforcements were in the form of commercial nanoparticles and alumina whiskers and their influence on mechanical properties were compared with the influence of synthesized alumina particles doped with iron oxide synthesized sol-gel technique. In order to test the mechanical properties of composite materials, the Brazilian Tests and the testing of the microhardness of samples were employed.

The subject of this study is the quantitative adhesion of a UV-curing composite film based on Bis-GMA (Bisphenol A glycidylmethacrylate) / TEGDMA (triethylene glycol dimethacrylate) as a matrix and particles doped with ferrous oxide on a metal substrate. Two different metal substrates: silver and gold-spattered brass with nickel intermediate coating were used in adhesion evaluating. Adhesion was measured using micro-identation and it was compared with the measured wetting angle of composites to the substrate. It has been shown that the substrates, although with similar mechanical properties that are reflected in very close hardness values, differ by achieved adhesive bonding with the polymer UV-cured polymer film. The addition of ceramic particles in the polymer matrix increased the adhesion of the composite film to both substrates, but the adhesion trend was dependent on the substrate type.

The aim of this paper is to investigate the mechanical properties of hybrid composites with the polymer matrix of the copolymer of ethylene and vinyl acetate (EVA), ultra high molecular weight polyethylene fibers (UHMWPE) and particles based on aluminum oxide. Commercial aluminum oxide nanoparticles and aluminum oxide particles obtained by sol-gel technique were used as fillers in a proportion of 1, 3 and 5 wt. %. Infrared spectroscopy with Fourier Transformation (FTIR) and Scanning Electron Microscopy (SEM) were used to test the chemical structure and microstructure of hybrid composites, respectively. The tensile test showed an increase in the modulus of elasticity and the tensile strength of the obtained hybrid composites. The results of the sample testing showed that the best mechanical properties and toughness of the material shows hybrid composites with 1 mass. % micron particles of aluminum oxide.

In the processes of preservation and restoration of sculptures and archaeological objects, copolymer materials of acrylate type are used because they have proved useful in conservation practice. The main disadvantage of acrylic resins is that they do not meet a more demanding conservation intervention. Because of this, composites are reinforced with particles to improve mechanical properties. Particle composites are made of 5 wt. %, 10 wt. %, and 15 wt. % of alumina based particles doped with ferrous oxide. The materials are determined by microhardness with a micro-Vickers mold suitable for composites. The results showed a significant improvement in microhardness of 7, 8.2 and 9.3 times compared to the polymer matrix without any filler. Examination of the behavior of the material under conditions that can be characterized as very aggressive was performed using cavitation. Cavitation damage of composite materials was tested with modified vibration cavitation. Surface erosion was determined during the experiment by measuring the loss of mass. The results show that the test material exhibits excellent mechanical properties and very good resistance to cavitation erosion.

Alumina (Al2O3) nano fibers are prepared from an aqueous solution of aluminum hydroxy chloride/poly (vinyl alcohol) (PVA)/water using the electrospinning technique. The weight ratio of aluminum hydroxy chloride/PVA was 5: 1. After calcification of fibers at 1100 ° C, continuous aluminum oxide fibers were obtained from 200 to 800 nm. The fiber morphology is characterized by a scanning electron microscope (SEM). Image analysis software (Image Pro Plus) was used to measure the diameter of the obtained aluminum oxide (Al2O3) fibers. The aim of this paper is to examine the mechanical properties of the hybrid composite, consisting of a polymer matrix (ethylene and vinyl acetate copolymer (EVA)), ultrahigh molecular weight polyethylene fibers (UHMWPE) and Al2O3 fibers obtained by electrospinning. Al2O3 fibers were added in an amount of 1 wt. % as shown by the improvement of the mechanical properties of the matrix and the hybrid composite.

Composite films having the UV cured Bis-GMA (Bisphenol A glycidylmethacrylate)/TEGDMA (triethylene glycol dimethacrylate) as a matrix and the ferrous oxide doped alumina (Al2O3 Fe) based particles were prepared and subjected to cavitation. In order to improve the mechanical and adhesion properties of composites, four different surface modifications of filler particles were performed: 3-methacryloxypropyltrimethoxysilane (MEMO), vinyl-tris(2-methoxyethoxy)silane (VTMOEO), (3-aminopropyl)trimethoxysilane (APTMS) and biodiesel (BD). Composite films were made with 0.5, 1.5, and 3 wt.% of ferrous oxide doped alumina particles with each of the mentioned surface modifications. Composite films were prepared on brass substrates and exposed to cavitation erosion. The erosion was monitored using the mass loss while image analysis was used to observe surface defects. The composite film reinforced with Al2O3 Fe having VTMOEO as a surface modifier was the most resistant one in terms of mass loss, as well as the level of surface destruction. Results were compared to the same polymer matrix film and composite films prepared with fillers without surface modifications revealing that all composites with surface modified fillers exhibited some improvement in resistance to cavitation. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. TR34011 and Grant no. III45012]

This paper presents the results of the laser cleaning effects on textile samples with corroded metallic threads. In many museum collections, there are textile exhibits like uniforms, national costumes, flags and home textile, embroidered with metallic threads. Corrosion of metal threads is one of the most common problems that damage embroidered items. In the practice, the application of conventional cleaning methods rarely gives the expected results, and the implementation of laser technology was the next step for corrosion products cleaning. The Nd: YAG laser was used to clean the corrosion of embroidered items from a museum study collection. The effects on the laser irradiated zones were investigated by optical and SEM microscopy and the EDX analysis. The laser irradiation process parameters of the metal threads corrosion.

Composites with the addition of alumina nanofillers show improvement in mechanical properties. The PMMA polymer was used as a matrix and two different types of nanofillers, having extremely different shapes were added in the matrix to form the composite. Reinforcements were based on alumina nanoparticles having either spherical shape or whiskers having the length to diameter ratio of 100. The influence of alumina fillers size, shape and fillers loading on mechanical properties of prepared composite were studied using the nanoindentation measurements and dynamic mechanical analysis. It was observed that both alumina whiskers and alumina spherical nanoparticles added in the PMMA matrix improved the mechanical properties of the composite but the improvement was significantly higher with alumina whisker reinforcement. The concentration of the reinforcing alumina spherical nanoparticles and alumina whiskers in PMMA matrix varied up to 5 wt. %. The best performance was obtained by the addition of 3 wt. % of alumina whiskers in the PMMA matrix with regard to mechanical properties of the obtained composite.

Modeling of the mechanical behavior of fiber-reinforced ceramic matrix composites (CMC) is presented by the example of Al2O3 fibers in an alumina based matrix. The starting point of the modeling is a substructure (elementary cell) which includes on a micromechanical scale the statistical properties of the fiber, matrix and fiber-matrix interface and their interactions. The numerical evaluation of the model is accomplished by means of the finite element method. The numerical results of calculating the elastic modulus of the composite dependance on the quantity of the fibers added and porosity was compared to experimental values of specimens having the same composition. [Projekat Ministarstva nauke Republike Srbije, br. ON174004 i TVH to project III45012]

Alumina based specimens having different content of alumina based fibers were investigated for possible application as cavitation resistant material. Cavitation damages of the alumina based specimens were tested by the modified vibratory cavitation set up. Erosion rates were measured based on the method developed for metallic samples, mass loss was measured during the experiment. Surface erosion was determined during the experiment simultaneously to mass loss measurements. Image Pro Plus Program was applied for surface analysis during testing. Results indicate that investigated material exhibit excellent mechanical properties and very good resistance to cavitation erosion. [Projekat Ministarstva nauke Republike Srbije, br. TR34011, br. TR35002 i br. III 45012]

Alumina based refractories are usually used in metallurgical furnaces and their thermal shock resistance is of great importance. In order to improve thermal shock resistance and mechanical properties of alumina based refractories short ceramic fibers were added to the material. SEM technique was used to compare the microstructure of specimens and the observed images gave the porosity and morphological characteristics of pores in the specimens. Standard compression test was used to determine the modulus of elasticity and compression strength. Results obtained from thermal shock testing and mechanical properties measurements were used to establish regression models that correlated specimen properties to process parameters.

In the framework of this research, the program Image Pro Plus was applied for determining the polymer-oxidizer interactions in HTPB-based composite propellants. In order to improve the interactions, different bonding agents were used, and their efficiency was analyzed. The determination of the quantity, area and radius of non-bonded oxidizer crystals is presented. The position of formed cracks in the specimen and their area have a great influence on the mechanical properties of composite propellant. The preparation of the composite propellant in order to enable the photographing of their structure by means of stereoscopic and metallographic microscopes with the digital camera is also described as well. .

Composite propellants are non-homogenous propellants and comprise primarily crystalline oxidizer and metal fuels uniformly suspended in a resin binder. The strength of the bonds between the polymer matrix and the oxidizer determine the mechanical properties of composite propellants. In order to achieve good mechanical properties of the fuel, bonding agents are added to the mixture. The role of the bonding agents is to enable good interactions (interphase) between the polymer matrix and the oxidizer grains. The level of interconnection between the phases could be measured by using the surface obtained by cutting the composite material and observing the resulting surface. A problem in the visualization of such a material is to enable the visibility of the polymer matrix and the grains in the image as both phases are white. There are two possible ways to overcome this problem: to add a pigment into the matrix polymer and to color the matrix and make it different from the grain color. Another possibility is to find a solvent for one of the phases and to dissolve one of the phases in an appropriate solvent so that the remaining phase could be stained, photographed and analyzed using the image analysis program. The morphological characteristics of the image could be established and analyzed. The topic of this study was to establish the conditions of preparation of composite propellants containing ammonium per chlorate and HMX and RDX as oxidizers, and polymer of the polybutadiene type and 1,3,5-trisubstituted isocyanurates as bonding agents. The bonding phenomenon was investigated by optical microscopy. The established procedure of preparation will enable the visualization of the composite structure and the morphological characteristics of the surface will be obtained. From the morphological properties of the obtained composite, it will be possible to select a suitable polymer for the preparation of uniformly distributed composite propellant.

Abstract Background Portable energy dispersive X-ray fluorescence (pEDXRF) spectrometry analysis was applied for the characterisation of archaeological ceramic findings from three Neolithic sites in Serbia. Two dimension reduction techniques, principal component analysis (PCA) and scattering matrices-based dimension reduction were used to examine the possible classification of those findings, and to extract the most discriminant features. Results A decision-making procedure is proposed, whose goal is to classify unknown ceramic findings based on their elemental compositions derived by pEDXRF spectrometry. As a major part of decision-making procedure, the possibilities of two dimension reduction methods were tested. Scattering matrices-based dimension reduction was found to be the more efficient method for the purpose. Linear classifiers designed based on the desired output allowed for 7 of 8 unknown samples from the test set to be correctly classified. Conclusions Based on the results, the conclusion is that despite the constraints typical of the applied analytical technique, the elemental composition can be considered as viable information in provenience studies. With a fully-developed procedure, ceramic artefacts can be classified based on their elemental composition and well-known provenance.

The most common scientific analysis of archaeological ceramics aims to determine the raw material source and/or production technology. Scientists and archaeologists widely use XRF-based techniques as a tool in a provenance study. After conducting XRF analysis, the results are often analyzed using multivariate analysis in addition to interpretation and conclusions. Various multivariate techniques have already been applied in archaeological ceramics provenance studies to reveal different raw material sources, identify imported pieces, or determine different production recipes. This study aims to evaluate the results of multivariate analysis in the provenance study of ceramics that belong to three cultures that settled in the same area during various prehistoric periods. Portable energy-dispersive X-ray fluorescence spectrometry (pEDXRF) was used to determine the elemental composition of the ceramic material. The ceramic material was prepared in two different ways. The ceramic body material was ground into powder, homogenized, and then pressed into tablets. After that, the same fragments are polished in suitable places. Quantitative and qualitative analyses were performed on the tablets and polished pieces. The results were subjected to both unsupervised and supervised multivariate analysis. Based on the results, it was concluded that qualitative analysis of the well-prepared shards' surface using EDXRF spectrometry could be utilized in provenance studies, even when the ceramic assemblages were made of similar raw materials.