نشریه پژوهش های کاربردی مهندسی شیمی - پلیمر
سال چهارم شماره 2 (پیاپی 12، تابستان 1399)

Research subject:

 The need to increase agricultural production in proportion to population growth and water crisis management requires initiatives that can increase the quantity and quality of crops by using soil moisture storage methods while preserving the environment. In this study, the effect of different wt. % of Thermoplastic starch (TPS) with maleic anhydride (MA) as compatibilizer and nanoclay (15A) on gel content and mechanical properties of Polylactic acid (PLA) and blends of  Linear low-density polyethylene/ Low-density polyethylene (LLDPE / LDPE) was evaluated.

Research approach: 

Here, 0, 10, 20 and 30 wt. % TPS were added to the blends of LLDPE/LDPE (20/80) and also PLA. Independent parameters in the experimental design were wt. % of TPS, basic polymer type that was PLA or TPS and aging test. For dependent parameters were considered gel content, tensile strength, elongation at break and elastic modulus. Experiments were designed in General Full Factorial Design and performed in three replications.

Gel content in LLDPE/LDPE blends increased with the addition of TPS and decreased for PLA blends. The gel content change range for experimental samples before and after the aging test was between 10 to 21 and 2 to 5 percent, respectively. Tensile strength and elongation at break were reduced by adding TPS in both series of compounds before aging test. But this reducing rate was less in the 20 wt. % of TPS. The values ​​of tensile strength and elongation at break were: 12 to 19 MPa and 50 to 350 percent, respectively. These values changed after the aging test between 7 and 11 MPa and from zero to 5 percent, respectively.
Keywords: biodegradability, low density polyethylene, poly lactic acid, thermoplastic starch.

Research subject: 

In water injection process, part of the surface active agents that are naturally present in oil can be dissolved in injected water. The presence of these substances affects the surface phenomena of the three phase water-oil-rock system. The effect of these substances on modification of the ionic composition of injected water has been less investigated in previous studies.

Research approach:

 In this paper, first, the effects of acidic compounds in crude oil and connate water composition on initial wettability of carbonate rock were investigated. Then to investigate the wettability changes of oil-wet calcite rock, single-salt aqueous solutions of MgCl2, CaCl2, KCl, and Na2SO4 having concentrations of 0.1 to 1 molar were used.Oil–water interfacial tension (IFT) for distilled water and salt waters in various concentrations were measured and compared. Variations of calcite rock surface properties were investigated by contact angle measurement after aging of thin sections in oil and salt waters.

Results indicated that by increasing ion concentration and ionic strength of salt waters, IFT decreases due to dissolution of acidic compounds of oil at the interface of oil and water. Moreover, for high content of acidic compounds in the oil, Magnesium ion has the most impact on reducing IFT and altering the rock wettability. So that by increasing the concentration up to 1 molar, IFT and contact angle decrease to 1 mN/m and 42 degrees, respectively.Contact angle measurements revealed that the composition of connate water is effective in changing the initial wettability of the rock, and formation of ionic-organic layer adjacent to the rock surface is one of the most important factors in wettability alteration. The presence of Magnesium ion in connate water decreases the contact angle to 145 degrees and causes the rock surface to become more water wet.Also, increasing solubility of oil-soluble acidic compounds in the aqueous phase has a significant effect on the rock wettability. The experimental results showed that the interaction between ions in the aqueous phase, especially the divalent ions, and surface active agents (carboxylic acid) determine the surface behavior of water in contact with oil and rock.

Research subject: 

In this research we studied the anti-corrosion properties of epoxy coating containing anti-corrosion pigment zinc phosphate with hydrophobic nano silica with different percentage also for determine the optimal conditions for preparation of nanocomposite Taguchi experimental design method was used.

Research approach: 

Anti-corrosion properties of epoxy coating under the influence of very important factors such as the percentage of nano silica, anticorrosive pigment and pigment to resin ratio according to model L9 taguchi method was studied and analyzed. Anti-corrosion properties of epoxy coatings were studied by electrochemical impedance spectroscopy test (EIS) in 3/5% NaCl aqueous solution and salt fog test (salt spray). To investigate the distribution of nano silica particles in epoxy resin were analyzed by transmion electron microscope (TEM) and scanning electron microscope (SEM). The results show that using from zinc phosphate and nano-silica was able to improve the corrosion resistances.

Results shows that addition of zinc phosphate and nano silica to epoxy resin caused a decrease in number of blisters and corrosion products after exposure to corrosion test based on the results in Nyquist and Bode plots, also the similarity in results was observed for the epoxy coating loaded according to the optimum conditions with 8% zinc phosphate, 3% nano silica and pigment to resin ratio of one according to salt spary. The significance levels of the experimental parameters, which indicate how the factors affect the compressive addition of zinc phosphate and nano silica to epoxy resin, were determined by using variance (Anova) method.

Research subject:

 In recent years, many efforts have been made to improve the performance of polymer membranes in oxygen-nitrogen separation due to the high cost and energy consumption of cryogenic distillation and adsorption methods. Increasing the performance of these types of membranes is still needed for industrial applications.

Research approach: 

In this research, novel magnetic mixed matrix membranes (MMMs) were prepared using polysulfone (PSf) as the main matrix, and also neodymium (Nd) as the magnetic particles for O2/N2 separation. To avoid the particle sedimentation and proper dispersion of particles across the membrane thickness, magnetic particle dispersion in the PSf was controlled by applying an external magnetic field (MF). The effect of Nd magnetic particle content on the microstructure, magnetic properties and thermal stability of the prepared MMMs were investigated using scanning electron microscopy, vibrating sample magnetometer and thermo-gravimetric analysis. In this reseach, a novel magnetic module was designed and constructed to investigate the performance of prepared membranes in the presence of various MFs.

The obtained results indicated that the permeability of O2 and N2 gases was improved by adding Nd magnetic particles into PSf matrix regardless of the amount of MF due to the chain packing of polymers disruption and free volume enhancement. The permeability of O2 and N2 in the MMMs containing 5 wt.% Nd in the absence of MF was about 182 % and 443%, respectively, higher than those of neat PSf membranes. Furthermore, the permeability and selectivity of PSf and PSf-Nd membranes were considerably improved by applying the MF during the permeation experiments. In the MMMs containing 5 wt.% Nd, O2/N2 selectivity was increased from 2.73 to 3.77 upon an increase in the intensity of MF from 0 to 570 mT. Considering the findings, the application of Nd particles and MF during the membrane preparation and separation processes can be facile methods for enhancement of membrane performance.

In the present study, the agglomeration and fragmentation of asphaltene particles have been simulated in laminar using the simultaneous coupling of Discrete Element method and Computational Fluid Dynamics. A new coalescence model according to the nature of asphaltene has been proposed. Asphaltene flocs have been considered as irregular shape rigid object. Particle collisions and collision efficiency as well as the fragmentation of asphaltene flocs have been studied in details. Furthermore, the asphaltene particles growth and change in particle size distribution along with average fractal dimension changes have been investigated. During the flocculation of the asphaltene particles, the asphaltene particles grow slowly in the initial times. It can be explained by the agglomeration of primary particles and the formation of asphaltene flocs. In the middle time period, due to the collision of the flocs and the formation of large flocs, the growth of the asphaltene particles increase. At the late times, the fragmentations limit the floc growth, and eventually asphaltene particle size approximately reaches a constant value in the steady state. The lognormal distribution provides the best fit for the asphaltene PSDs which, according to previous studies, is also consistent with the nature of asphaltene. The results of proposed collision and fragmentation kernels based on simulation results are agreed well with previous studies.

Research Subject: 

One of the important methods in the treatment of skin wounds is the use of wound dressings. Recently, the use of polymer-based wound dressings has become increasingly common. The use of natural polymers is very important in wound dressings. The aim of the present study is to design and manufacture a polyvinyl alcohol/aloe vera wound dressing with the capability of healing skin wounds.

Research Approach:

 The electrospinning method was applied to prepare the samples. Aloe vera gel was first extracted, purified, and powdered by freeze-drying. In all samples, the amount of polyvinyl alcohol and aloe vera powder was fixed at 8 wt.%. This value was selected empirically based on the quality of the produced fibers. Different samples including different amounts of polyvinyl alcohol and aloe vera were produced and their properties including morphology, tensile strength, swelling, degradability, and antimicrobial properties were investigated.

The results showed that the dropless random oriented fibers with uniform diameter were produced. The diameter increased with increasing aloe vera contribution, which was attributed to an increase in viscosity due to the presence of aloe vera. With increasing aloe vera contribution in the samples, tensile strength decreased and the elongation percentage increased. The swelling behavior of the specimens was evaluated by measuring the weight of the specimens in a simulated skin environment and the results showed that the presence of aloe vera increased the hydrophilic properties of the specimens. Antimicrobial activity of the samples against two gram-positive Staphylococcus aureus and Gram-negative Pseudomonas aeruginosa was investigated using the disk diffusion method and it was found that the presence of Aloe vera in the samples brought antimicrobial activity against Pseudomonas aeruginosa. Finally, the findings of this study confirm the feasibility of using polyvinyl alcohol /aloe vera for the production of the electrospun wound dressing.

The porosity of electrospun nanofibers web is a significant parameter affecting various areas of nanofibers applications. Thus, at first, the effect of most effective parameters, the concentration of polymer solution and flow rate, on the diameter of polyvinyl alcohol nanofibers, as a dissolving component, were investigated. Afterward, the hybrid web of polyamide 6/polyvinyl alcohol (PA/P) was prepared via a two-sided dual-nozzles electrospinning method. The morphology, diameter, pore size of nanofibers web and the effect of dissolving constituent were studied based on images of the scanning electron microscope. To measuring the porosity of nanofibrous webs, three practical and straightforward methods that have been proposed in the literature were utilized. It was observed that when one component was dissolved, the diameter of the resultant web was decreased, and the porosity has been reduced to about 70% based on the best selected method of porosity. Additionally, the average pore size of electrospun PA6 webs has been decreased about 30-58% relative to the original hybrid webs.

Research subject: 

Regarding to temperature effect on the rate of corrosion in absorption tower of gas refineries, it is very useful to examine and invest on new methods to decrease the temperature in mentioned towers.

Research approach:

 By studying different types of corrosion in amine processes and the influence of different variables on them, the dominant effect of temperature on the rate of corrosion in absorption towers was determined. Due to decreasing temperature in the absorption tower the surface tension of amine solvent and corrosion rate decrease. The reduction in surface tension reduces the foaming and flooding in the tower, which reduces the concentration of sour gases CO2 and H2S from the natural gas outlet. Various methods of reducing temperature in the absorption tower such as increasing flow rate of circulation amine solvent, opening the insulated tower wall and injecting amines into the middle of the tower have been studied. Aspen- HYSYS software was used to investigate the effects of amine injection into the middle of the tower.

According to the simulation results, the maximum temperature in the two-feed absorption tower was reduced to about 3°C and in the three feedstocks the maximum temperature was reduced to about 10°C. Also, as the CO2 and H2S concentration of the gas outlet decreases, the amount of Spent Caustic and catalyst in the lower part of the tower will decrease. Finally, it was found that among the above methods, injection of amine into the middle of the tower had the highest efficiency in decreasing the temperature of it. However, a combination of the above methods can be used to further reduce the temperature in the tower.