جستجوی مقالات مرتبط با کلیدواژه « سنتز » در نشریات گروه « مهندسی شیمی، نفت و پلیمر »

Research subject: 

Electromagnetic heating is one of the new methods of upgrading and increasing heavy oil extraction. In this method, electromagnetic waves will increase temperature, break heavy compounds, reduce viscosity, and improve and increase oil recovery.

Research approach:

 In this research, magnetic iron oxide nanoparticles (Fe3O4) were synthesized by the co-precipitation method, and the efficiency of these nanoparticles in the process of electromagnetic heating and heavy oil upgrading was investigated. Also, a comparison was made between the effect of these nanoparticles in the process of electromagnetic heating and activated carbon. In this process, oil samples containing 0.1% of Fe3O4 nanoparticles or activated carbon were irradiated with microwave (frequency 2.54 GHz and power 400 W) for 0 to 8 minutes, and the temperature and viscosity variation were investigated.

The results showed that microwave radiation increased the temperature of the samples. The temperature of the sample of crude oil, crude oil with activated carbon, and crude oil with Fe3O4 nanoparticles increased from ambient temperature to 70, 82, and 90°C, respectively, under wave radiation for 8 minutes. Also, the most significant decrease in viscosity was reported in 4 minutes: the viscosity of crude oil sample, crude oil with activated carbon, and crude oil with Fe3O4 nanoparticles under wave irradiation for 4 minutes decreased 295 mP.a to 261, 254, and 223 mP.a, respectively. In other words, the viscosity of the samples under wave irradiation for 4 minutes for crude oil, crude oil with activated carbon, and crude oil with Fe3O4 nanoparticles decreased by 11.5, 13.9 and 24.4%, respectively.

Today, the specialists’ attention on polyurethanes is increasing day by day due to easy synthesis, available raw materials, favorable mechanical properties, biocompatibility, and the possibility of providing different products, such as water-based polyurethanes, foams, hydrogels and glues. Chitosan is a natural polymer that is extracted from the deacetylation of chitin and contains glucosamine and N-acetyl glucosamine units. This non-toxic natural polymer has very useful properties such as antimicrobial activity, biocompatibility, biodegradability, and tissue repair and regeneration effects. One of the weaknesses of chitosan is its poor solubility and processability due to its strong intra- and intermolecular hydrogen bonding. Therefore, chitosan has been used mainly in modified form or in combination with other polymers in various applications. The combination of synthetic polymers with natural polymers is of particular importance because natural polymers such as chitosan can show some properties such as biocompatibility, biodegradability, low toxicity, high cell viability, and internal tissue growth; while the synthetic polymers have other characteristics such as favorable processing, mechanical and physical properties, and appropriate chemical and thermal stability. Recently, chitosan has been used in combination with polyurethanes to improve its mechanical properties, thermal stability, biodegradability, antimicrobial properties and biological activity. During these studies, products in various forms such as composite, elastomer, fiber, foam, scaffold, and hydrogel have been prepared for different applications. In this review, polyurethanes containing chitosan and their synthesis methods for various applications are discussed. The products prepared in these studies have been suggested for various applications such as antibacterial coating, wound dressing, tissue engineering scaffold, fabric modification, fibers, hydrogels and foams.

Today, the prevalence of bacterial infections and their resulting human and financial losses has led scientists constantly to seek solutions to develop knowledge in controlling these pathogenic microorganisms. Bacterial adhesion and their growth on different surfaces cause the accumulation of these microorganisms and the formation of biofilms. These developed microcolonies can grow and detach from the surface and spread infections. Therefore, the best way to prevent spreading the infections and diseases is to prevent the formation of biofilms using antimicrobial surfaces. In this regard, one of the most important tools introduced is the use of antibacterial polymer coatings. Polyurethanes have received much attention due to their unique properties such as biocompatibility, the possibility of using various raw materials, and controllable properties. In recent years, waterborne polyurethanes have been extensively studied due to less frequent use of volatile organic compounds (VOCs) in their preparations, easy fabrication, low viscosity, the possibility of spraying, high adhesion to different surfaces, high abrasion resistance, ability to disperse a variety of additives, and rapid film formation in biomedical fields such as antibacterial coatings, wound dressings, and biological products. In this review article, first, the various methods of preparing antibacterial polymer coatings are described. These methods include the use of nanostructures, combined with antibacterial polymers, and the use of antibacterial monomers. As a result, polyurethanes and waterborne polyurethanes have been developed. The following is a review of studies on the preparation of antibacterial waterborne polyurethanes using different strategies such as the addition of nanostructures, blending with antibacterial polymers, drug loading, the use of antibacterial monomers, and polymer surface modification. The products developed during these studies have been proposed for a variety of applications such as medical equipment coating, wound dressings and packaging industry.

This study used cellulosulfonic acid as a new catalyst for synthesizing azo dyes based on naphthol, xanthene, and hydroxycoumarin. Also, cellulosulfonic acid catalyst was recyclable and was used in five steps. The structure of the synthesized compounds was determined by comparing their physical properties with previously reported values using IR and HNMR spectroscopy data. The results showed that these synthetic reactions are elementary and produce azo dyes with good efficiencies. The advantages of the proposed method are the avoidance of environmentally harmful solvents, mild conditions, high speed and short reaction time, simplicity of working up process, high efficiency, and purity of synthesized derivatives.

Engineering and biological properties of pyrimidines have stimulated chemists to develop the chemistry of these compounds as dyes and organic-metal complexes. Metal complexes of monoazo compounds are principally useful as metal complexes for dyeing of protein, polyamide and engineering materials and Countless shades from greenish yellow to deep black can be generated, depending upon the metal, the dye ligands, and the combination of dye ligands in mixed complex dyes. In this research for the first time a number of new azo dyes were synthesized by coupling 4, 6- dihydroxy pyrimidine with diazotized heterocyclic aromatic and nonheterocyclic aromatic amines. Then one of the synthesized dyes and also 4, 6-dihydroxypyrimidine was used as ligands to preparing some new Azo and Azo-metal (Cupper (II), Nickel (II) and cobalt (II)) complexes. Studies have shown that some metals such as Copper (II) reacts with the other nitrogen and oxygen atoms in the pyrimidine ring at a ratio of (3: 2) in addition to the covalent coordination with the azo group and the hydroxy pyrimidine group. The structures of all synthesized compounds were confirmed by instrumental and elemental analysis (C.H.N.). The antibacterial activity of the selected products was examined. Some products contain donor group like methyl exhibit promising activities.

Due to the unique properties of shape memory polymers (SMPs) including low density, good price, high deformability, reproducibility, molecular tailoring and good processing many applications have found for these materials in different fields. Shape memory properties of the nanocomposite samples based on polyurethane/graphene nanoplatelet (GNp) were investigated. The improvement in performance of SMPs by adding graphene nanoplatelet is the main hypothesis of this study. At first, two types of polyurethane were synthesized using different formulations (for obtaining the samples with different hard segments) and then nanocomposites samples including GNp were produced through solution method.  Two different polyurethanes with hard segment contents of 23.9% and 24.4% were synthesized. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), shape fixity and shape recover values of the samples (as indices of shape memory properties) were employed to characterize the synthesis of polyurethane and performance of shape memory behavior of the nanocomposites.    The FTIR spectra showed that the formation of polyurethane was successfully accomplished. The SEM micrographs confirmed the good dispersion of nanoparticles in the matrix and there were no agglomerations and aggregation of particles. No characteristics peaks (crystallization and melting peaks) were observed in DSC thermograms for samples based on toluene di-isocyanate which means the synthesized polyurethane was fully amorphous without crystalline and regular regions. While the samples based on hexamethylene di-isocyanate showed the regular and crystalline regions. Shape fixity and shape recover values of the samples were in the range of 70-90%. These indices were increased by GNp addition.

The microwave-assisted has been regarded as a new strategy in the synthesis various organic compounds especially organic dye. The technique offers a lot of advantages as it is simple, rapid, economic and efficient. Dyes are effective molecules have pivotal effects in several fields. Organic dyes were endowed with a diverse of photophysical and photochemical and biomedical applications. Novel microwave synthetic method for many types of dyes including naphthalimides, phenothiazines, fluorescein, pyridinones, cyanines, quinolines, coumarins, triazoloquinoxalines and monoazo disperse dyes were demonstrated. Factors like temperature, type of solvent and power control microwave reactions. Microwaves possess the potential to transport energy from one medium to another in a small duration of 10−9 s with every run of electromagnetic energy. This review highlights microwave applications for the synthesis of dyes with fluorescence, luminescence and photophysical properties.

Black titanium dioxideNano pigments can retain daylight from UV to infrared wavelengths, since its optical absorption properties, and is presented as a good light absorber contrasted with titanium dioxide. Ongoing improvements in the field of black titanium dioxide have plainly shown that these materials are generally utilized in innovative work, because of their exclusive structural properties, for instance, surface disordered, oxygen vacancy and Ti3+ ions and their appropriate electronic properties, which are because of their narrow band gap, have been utilized in different applications, for example, photodegradation of dyes, photocatalytic and photoelectrochemical water splitting, batteries, super capacitors, fuel cell, hydrothermal treatment of cancer, and solar cells. Various approaches have been reported to prepare black TiO2 such as hydrogenation, chemical reduction with different metal like Al, Zn and Mn, chemical oxidation, ultrasonication, anodization-anilling and laser modification. This paper focused on the synthesis method, properties and applications of these Nano pigments briefly.

Gel treatment is one of the most promising remedy methods to improve conformance in heterogeneous reservoirs for better sweep efficiency. In this paper, new enhanced preformed particle gels (PPGs) for conformance control at the Balal reservoir are introduced. In these PPGs, three species of 2-acrylamido-2-methylpropane sulfonic sodium salt (AMPSNa), acrylamide (AM) and N-vinylpyrrolidone (NVP) monomers have been used to synthesize via free radical crosslinking polymerization at room temperature using N,N-methylenebis (acrylamide) (MBA) as a cross linker. The swelling properties of the PPGs were enhanced by adding the Nano clay Montmorillonite Na+. A temperature stability agent was also used to make these special PPGs compatible with high temperature and salinity reservoir conditions. Then, PPGs were kept in Balal reservoir conditions in order to study their stability in harsh reservoir conditions. To this end, combination of 50 samples of the preformed particle gel has already been constructed by design of experiment using response surface method, and finally a new model for predicting the swelling ratio of the preformed particle gel based on the weight percentage of material and in different salinity is provided. The results of this research show that the crosslink has more influence on the swelling ratio, and PPG with the optimal formulation will able to guarantee the hard reservoir conditions (temperature 82˚C & salinity 260000ppm).

Polymeric materials carrying positive and/or negative charges at neutral pH are referred as "polyelectrolytes". Many kinds of materials are considered as polyelectrolytes because they bear ionic groups of positive or negative charges on their surfaces. The interaction between two or more opposite charged polyelectrolytes in solution forms a polyelectrolyte complex (PEC). Polymers used for PEC formation are classified on the basis of origin as natural and synthetic. The worldwide agreement among investigators is that the PEC formation is an entropy-driven phenomenon. The contributing force for the formation of PECs in aqueous solutions is the release of low molecular weight counter ions (which were previously associated with the charged groups on polymer chains) that result in an increase in entropy of the system. PECs have many advantages such as high biodegradability, excellent biocompatibility, non-toxicity, low cost, low energy requirement for their production. There are numerous parameters affecting PEC formation including charge density, molecular weight, and salt concentration, pH of the reaction medium, ionic strength and mixing ratio. This article presents the properties of PEC, mechanism of PEC formation, factors affecting the formation of PEC, different methods for PEC synthesis and application of PECs. PEC is an emerging system for drug delivery to target sites, sustained and thereby prolonging the therapeutic action. They are also used in gene, protein and vaccine delivery, tissue engineering and fabrication of membranes.

Poly (N- vinylpyrrolidone -co- maleic anhydride) @ eggshell @ Fe3O4 (PNVPMA@ES@Fe3O4) eco-friendly nanocomposite was synthesized by a two-step method. In the first step, the PNVPMA copolymer was synthesized via radical polymerization method. In the second step, the PNVPMA@ES@Fe3O4 nanocomposite was synthesized through an in-situ co-precipitation technique. The PNVPMA@ES@Fe3O4 nanocomposite was used as high performance eco-friendly adsorbent to remove Congo red (CR) dye from aqueous solutions at various conditions, such as pH effect, contact time, adsorbent dosage and dye concentration. Results showed that the percentage removal of CR by synthesized magnetic nanocomposite was more than 95% at pH=6 and contact time 30 min. The results showed that the interactions between CR and the PNVPMA@ES@Fe3O4 nanocomposite were in agreement with the Langmuir isotherm and pseudo second order kinetic model. Also, thermodynamic model showed that the CR adsorption on the synthesized nanocomposite was spontaneous.

Different macromonomers having polyethylene glycol branches were synthesized via esterification reactions in various conditions. Quaternary polymers were prepared using synthesized macromonomers of polyoxyethylene acrylate and methacrylate with a PEG molecular weight of 600-3000 g/mol, and sodium acrylate, sodium methacrylate and sodium maleate. The superplasticizers were synthesized by free radical polymerization in water medium at 65-80oC. The recipe and polymerization conditions have a direct effect on the structure of superplasticizers. The structures of the synthesized quaternary polymers were characterized by 1H NMR, Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC) analyses. The efficiency of a superplasticizer depends on the size of main chain, the chemical structure of repeating unit, molar ratio of monomers, chain-to-ion molar ratio (B/I) and size of the branches. These structural parameters affect the geometrical restriction, adsorption and the interaction between the superplasticizer chains and cement particles. FTIR, thermal gravimetric analysis (TGA) and X-ray powder diffraction (XRD) methods were also used to characterize the effect of superplasticizer structure on the hydration reaction of the cement pastes. FTIR spectroscopy was used to explore the effect of superplasticizer structure such as branch length and chain-to-ion molar ratios on the structure of the hydrated calcium silicate gels, polysilicate (SiO4-2) and calcium hydroxide generated during 7 days hydration. The results of XRD indicated that the structure of superplasticizer affects the content of anhydrous phase and hydrated products during hydration. The increase of PEG branch length slightly increased the decomposition temperatures of the hydrated calcium silicate gels and calcium hydroxide crystals. Furthermore, the size of calcium hydroxide crystals changed with the superplasticizer branch size.

Making polymer alloys, copolymerization, functionalization, preparing polymeric composites using inorganic components or adding additives such as plasticizers and stabilizers to polymers are new strategies to modify polymers suitable in new applications. Among these methods, functionalization of polyolefins counts as a useful strategy for synthesis of new materials with improved properties. Functional groups change the important properties of polyolefins such as adhesion, penetration, compatibility, resistance to solvents, rheological and surface properties like colorability and printability, therefore, the functionalization can extend their application to other fields including adhesives, colors and insulators.To obtain a polymer with some particular properties, besides the type of functional groups, it is necessary to control their contents. Therefore, development of methods for controlled synthesis of functionalized polyolefins by conventional industrial monomers has achieved great interest in academic and industrial research. In this paper, several different methods for synthesis of functional polyolefins, their properties and applications are discussed in brief.

Despite the widespread applications of conductive polymers, their usage has been limited due to their poor processability. Emulsion polymerization to produce stable nanoparticles in water, solve to some extent the difficult process of these polymers. In this study, synthesis of polyaniline by inverse emulsion polymerization method along with chemical, physical and structural aspects is discussed. Synthesize of conductive polyaniline is carried out using oxidizing agent of benzoyl peroxide in a non-polar solvent, a functionalized protonic acid as dopant/ emulsifier and hydrochloric acid to improve the product conductivity. In order to optimize efficiency and conductivity of synthesized polyaniline, the effect of synthesis conditions such as reaction time, type and concentration of reactants were investigated. Synthesizing in optimum condition, minimum resistance value for a produced polyaniline was about 8.29 Ω. Beside conductivity, morphology and other properties of polyaniline has been investigated by FT-IR, SEM, DSC and DLS analysis.

In this research polyethylene glycol urethane acrylate was synthesized as a nonionic linear polymeric dispersant based on polyethylene glycol (PEG)، isophorone diisocyanate (IPDI)، hydroxyethyl methacrylate (HEMA) in presence of dibutyltin dilaurate (DBTDL) as catalyst and acetone as a solvent. The nonionic polyethylene glycol urethane acrylate dispersant was characterized by Fourier Transform Infrared (FT-IR) and Proton Nuclear Magnetic Resonance (1H-NMR) and molecular weight was measured by Gel Permeation Chromatography (GPC). Besides، the dispersants were used for dispersing of TiO2 and dispersion quality and distribution was determined by Grindometer. The results indicated that because of steric protect dispersant، suspension particle size decreased. Also dispersant with the medium molecular weight and chain length، showed a better performance on the stabilization of particles of TiO2. J. Color Sci. Tech. 9 (2015)، 217-223©. Institute for Color Science and Technology.