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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.

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 subject of this research is the production process of polyvinyl chloride (PVC) regranulate using a plasticizer synthesized from recycled poly(ethylene terephthalate) (PET). In this way, a plasticizer was synthesized that does not pose a risk to human health and the environment in accordance with the principles of chemical leasing and green chemistry. The obtained plasticizer was characterized using elemental analysis, FTIR, and NMR spectroscopy and determination of hydroxyl and acid number. The mechanical properties of materials obtained on the basis of recycled PVC and plasticizers from PET were tested according to standard methods.

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.

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.

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]

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.

It is well known that alumina possesses good mechanical and chemical properties. Nanofibers having α - alumina structure was used as reinforcement for metal, polymer and ceramic matrix composites. In this study, three series of nanofibers were prepared. The first series was made from 10 % water solution of the aluminium chloride hydroxide/polyvinyl alcohol with a mass ratio of 5:1. The other two series were made with the addition of 1 wt.% of MgCl2 or 1 wt.% of FeCl3 regarding the aluminium chloride hydroxide content. Nanofibers were prepared using the electrospinning technique and they were characterized by the TGA/DTA, XRD and FESEM methods. It was proven that addition of FeCl3 into the initial spinning solution lowers the temperature for the corundum structure formation while the addition of MgCl2 results if the formation of mixed oxides that eases the sintering process. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. TR34011]

Commercial alumina wiskers (Al2O3 w) and synthesized alumina particles via sol-gel technique (Al2O3 m) were used as reinforcement in unsaturated polyester resins (UPR). Composite materials with the addition of 0.1 wt. %, 0.25 wt. %, 0.5 wt. %, 1.0 wt. %. i 2.5 wt. % of alumina based particles were obtained. Structural analysis of used alumina reinforcement and obtained UPR/Al2O3 composites was performed by FTIR spectroscopy. Morphology was studied by scanning electron microscopy (SEM). The microhardness test was done using the Vikers method. Obtained results showed an increase of microhardness of UPR/Al2O3 w composites up to 66.4%, while the increase of microhardness of UPR/Al2O3 m composite was up to 52.3% compared to UPR matrix.

Ferric oxide doped alumina particles were prepared via the sol-gel method and their performance as Reactive Orange 16 adsorbent was evaluated. The concentrations of the Reactive Orange 16 were monitored using a UV-Vis spectrophotometer. The effect of Reactive Orange 16 concentration, adsorbent quantity and pH on the solution decolorization efficiency was analyzed. The efficiency of the Reactive Orange 16 removal using ferric oxide alumina doped exceeded 98 % in 20 min at pH=3. The experimental data were fitted to the Langmuir equation better than to the Freundlich one. The pseudo-first-order model fits well with the experimental data for adsorption kinetics. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. TR34011]

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.

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.

This paper presents the optimized technological process for obtaining stable calcium carbonate dispersion (CaCO3) in accordance to the standard prescribed in the paper industry. The reason for using CaCO3 in paper production is their low price when compared to the cellulose fibers and its ability to improve the properties of the final product. However, CaCO3 is alkaline filler that has relatively poor chemical stability that may affect the characteristics of the paper. For this reasons it is necessary to optimize the technology for obtaining a stable dispersion of CaCO3 with particles diameter in range 1 mm

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]

Dental materials have specific requirements regarding behavior in exploitation conditions. Poly (methyl methacrylate) (PMMA) is one of the most commonly used prosthetic materials. It is of interest to improve the mechanical properties of the polymer matrix by adding reinforcements in the form of ceramic particles. It has been shown that adding very small amounts of particles to the material, substantially improved mechanical properties of PMMA modified by dimethyl itaconate (PMMA/DMI). In this paper, different sorts of alumina fillers will be examined. Commercial alumina particles and micro particles of alumina obtained from the sol-gel technique influence the mechanical properties of the composite material obtained. Sol-gel techniques was the mean to synthesize pure alumina particles and ferrous oxide doped alumina particles. Composites are prepared with 1 wt. %, 3 wt. % and 5 wt. % of alumina based particles. It has been shown that all the tested fillers improve the flexular properties of the material relative to the pure matrix PMMA/DMI and the most suitable concentration of fillers was 1 wt. %. Among the types of fillers tested alumina particles obtained by sol-gel technique, perfomed in the best way in improving the flexural strength and modulus.