نشریه پژوهش های کاربردی مهندسی شیمی - پلیمر
سال چهارم شماره 1 (پیاپی 11، بهار 1399)

The use of nanoparticles, especially nano-antibiotics, increases their efficacy. More uniform release of antibiotics is one of the benefits of being nano. They can also be made using ointment or banderol to absorb through the skin to the infection, thereby reducing its side effects. Amoxicillin is one of the most widely used antibiotics in the world which can be prevented by increasing the use of other strong antibiotics if promoted as nanoparticles. Determining the mechanism of nanoparticle formation of this drug is an important factor for its commercial production.

The purpose of this study was to determine the nucleation mechanism and time of induction of crystallization of amoxicillin nanoparticles in the presence of surface active agents ‘CTAB’ and ‘SDS’. Therefore, the effect of amoxicillin concentration and stabilizing concentration on the crystallization process was investigated. In this project, a combination of inductive-reactive crystallization was used. In this method, amoxicillin sodium was produced with sodium hydroxide, amoxicillin sodium, has a much higher solubility in water. Then, by adding hydrochloric acid, amoxicillin will be recovered and supersaturated. SEM and DLS analyzes were used to determine the properties of amoxicillin nanoparticles. All the experiments were repeated twice.

The results show that particles with a mean size of 50 nm were formed, and the particle stability was confirmed up to one week after formation. The results of the experiments show that the nucleation mechanism is the primary type with an average explanatory factor (R2) equal to 0.9887 and adding a stabilizing agent has no effect on the nucleation mechanism.

 In recent years, the use of graphene nanoplatelets (GnPs) in polymer nanocomposites has attracted considerable attention. Dispersion state of GnPs in the polymer matrix has a great importance which can affect microstructure and final properties of nanocomposite. Therefore, in the present work, the effect of compatibilizer on the dispersion state of GnPs and also on internal structure, orientation, and tensile properties of polypropylene (PP)/GnPs nanocomposite fibers are investigated.

 PP/GnPs nanocomposite fibers containing 0.1% and 0.5% GnPs with and without maleic anhydride-grafted polypropylene (PP-g-MA) were melt spun. Dispersion state and location of GnPs in the nanocomposite fibers were investigated by transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS). Fiber orientation and crystallinity were studied by polarized Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC), respectively. Moreover, fracture behaviour of PP/GnPs nanocomposite fibers was investigated by cross-sectional scanning electron microscopy (SEM) images of tensile fractured samples. Using Halpin-Tsai model, experimental tensile moduli of fibers were compared with the predicted values. 

TEM images show that in the compatibilized PP/MA/GnPs nanocomposite fibers, GnPs aggregates decrease and their size also reduces, suggesting that GnPs dispersion improved. An increase in Lp of the compatibilized sample recorded from SAXS analysis indicates that the more GnPs are located in the intrafibrillar region. Based on polarized FTIR and DSC results, orientation and crystallinity of PP/G0.5 nanocomposite fiber are found to significantly increase after inclusion of PP-g-MA. Moreover, reinforcing effect of GnPs in PP/MA/GnPs nanocomposite fibers could be explained by better GnPs dispersion and changes in internal structure of fiber. Furthermore, the tensile fracture behavior of PP/GnPs nanocomposite fiber changes from ductile to brittle in the presence of PP-g-MA.

Methane hydrate reservoirs as an unconventional resource of natural gas can secure demand of energy in the world for many years. Efficient production prom this resources is the subject of concern. CO2-Methane replacement is a novel method for production from naturally occurring methane hydrate deposits such that methane production and CO2 storage take occur simultaneously.

 In this study a new kinetic model is proposed for CO2-Methane replacement in hydrate structure. This kinetic model is developed based on the mechanism proposed for replacement in the hydrate structure in the presence of excess water in a slurry phase of methane hydrate. According to this mechanism partial breakage of methane hydrate cages, methane-CO2 substitution and formation of CO2 hydrate proceed simultaneously. Methane hydrate dissociation and CO2 hydrate formation kinetic parameters are evaluated experimentally and fitted on polynomials as function of pressure and temperature.

Evaluation of the effects of pressure and temperature on the replacement efficiency show that higher replacement efficiency is obtained at higher temperatures and lower pressures. It means that replacement kinetic is controlled by methane hydrate dissociation step. Since, higher temperature and lower pressure favor dissociation of methane hydrate. At 278.15 K the replacement efficiency decreased from 15.78 to 8.80 as total pressure increased from 55 bar to 65 bar, at 280.15 K it decreased from 26.98 to 15.91 by decreasing total pressure from 60 bar to 70 bar. At same pressure 60 bar for 280.15 K and 278.15 K the replacement efficiency is 20.96 and 11.59 respectively.

Zinc is one of the most dangerous organic components in industrial wastewaters, which pollutes the environment as a result of human activities and various industrial operations. In the present study, the adsorbent prepared from Gracilaria Corticata algae was used for the first time to recover and remove heavy metal zinc and equilibrium study of the process were done.

In the current work, the effect of important parameters such as initial pH of solution, adsorbent dosage and contact time were investigated on the adsorption efficiency of the process. Additionally, Langmuir and Freundlich two-parameter adsorption isotherm models were used to model the equilibrium of zinc adsorption.

The results showed that according to the calculated correlation coefficient, Freundlich isotherm was better than the Langmuir in fitting the experimental data. The highest point-to-point correlation coefficient for adsorbent percentage was achieved at 3 g/ml adsorbent dosage with contact time of min 360 and pH=7 and the lowest one was at 4 g/ml adsorbent dose with contact time of min PH=360 and 7. However, the highest adsorption rate was observed for the adsorbent dosage of 4 g/ml with contact time of 420 min at pH=9 and the lowest adsorption percentage was achieved at the adsorbent dosage of 2 g/ml with contact time of 300 min and pH=5. The maximum and minimum adsorption percentages were 76.88 mg/g and 49.25 mg/g, respectively

 Increasing plastic wastes of the packaging industry and concerns about their environmental problems, have attracted many researchers to use biopolymers. Therefore, the preparation of cheap biodegradable films with desirable properties for using in the packaging industry can be an attractive challenge.

In this study, poly (lactic acid) (PLA) based ternary blends were prepared by experimental design (mixture method). For this purpose, thermoplastic starch (TPS) was first prepared using 28 wt% sorbitol and 14 wt% glycerol. Then, PLA / PCL (poly (caprolactone), PCL) / TPS ternary blends at different concentrations were prepared using the melt mixing method. Morphological, physical (tensile, water vapor permeability), biodegradability, and rheological tests were also carried out. Finally, the optimum sample was determined using Minitab software.

Scanning electron microscope (SEM) images revealed incompatibility and phase separation in the blends. Moreover, with increasing PCL and TPS contents, flexibility enhanced due to the plasticization effect of PCL and mechanical properties declined, respectively. The permeability test results showed that the samples containing less TPS due to its hydrophilic nature and more PCL leads to increase the crystallinity of the matrix, had lower water vapor permeability. The effect of TPS on the biodegradability test was also well established. In this way, the sample containing 35 wt% TPS loses about 50% of its weight within 14 weeks. Finally, the sample with 50/25/25 (PLA / PCL / TPS) composition was selected as the optimum sample by Minitab software. The results showed that the formulated films in this study have the potential to be used in biodegradable packaging materials with good mechanical and barrier properties.

 In recent years, researchers have proposed various methods for gas separation because of rising greenhouse gases in the atmosphere and causing enormous environmental problems. One of the newest and emerging methods is membrane gas separation. In the last decade, mixed matrix membranes (MMMs) have received much attention due to their ability to successful separation of polar gases from mixtures.

In this study, a novel two-component mixed matrix membrane was prepared by incorporating the nickel zinc iron oxide nanoparticles into the Pebox polymer matrix. This is owing to combination the unique features of Pebax copolymer such as high mechanical strength and gas permeability, with nanoparticle properties as considerable permeability and selectivity, and appropriate mechanical and thermal stability. The gas permeability test was performed for pristine membrane and MMMs at 35 °C and pressure range from 2 to 10 bar. Fabricated membranes were also evaluated by FESEM, FTIR-ATR, DSC and XRD tests

Results demonstrated that in the case of the optimum membrane with 1 wt.% of filler loading and at 10 bar, the CO2 permeability was increased about 128% and reached to 278 Barrer, compared to pristine membrane. However, the CO2/CH4 and CO2/N2 selectivities were improved by 175 and 183 percent, respectively. This superior results was due to the presence of iron, nickel, and zinc atoms in the filler structure, which resulted in a better interaction with CO2. On the other hand, the presence of CO2-friendly segments in the Pebax structure caused much higher CO2 permeability in comparison with other light gases.

 The rubber Springs with spong structure must have acceptable tear resistance in addition to desirable compression set. Usually enhancing each of these properties leads to the weakening of the other property.

 Simultaneously providing the optimum value of these two properties in the rubber spring compound requires consideration of the effective factors by performing several tests. Therefore, in this study, a test plan based on the Taguchi statistical analysis technique was presented to design the optimal formulation in exchange for reducing the number of tests required. Thus, the impact of four factors: weight percent of Natural rubber (NR), concentration of zinc oxide (ZnO), dicumyl peroxide (DCP) and ethylene glycol dimethacrylate (EDMA) on the ratio of tear resistance to compression set (design criterion, Q) was determined.

Data given of ANOVA showed that the amount of DCP with 66.93% has the highest influence on the design of the rubber spring compound. In addition, it was revealed that the curing system is a solution for the simultaneous optimization to maximum tear energy and minimum compression set of the compound. Statistical analysis predicted that the optimal formulation contained 60 weight percent of NR and 1, 4 and 2 phr of DCP, ZnO and EDMA, respectively. Experimental test results confirmed the predicted Q value for optimal conditions.

Nanocomposites are a new class of materials that have at least one of their major constituents, at least in one dimension, in the range of one to one hundred nanometers. Typically, nanocomposites have different and superior properties in terms of mechanical and physical properties than conventional composites.

In this study, polyvinyl acetate was prepared by emulsion polymerization for polymer matrix. Then the diamond nanoparticles were modified with silane agent. Finally, polyvinyl acetate / diamond nanocomposite was prepared and analyzed with 0.5, 1, 1.5 and 2 wt% of modified diamond nanoparticles. To determine the properties and structure of the nanocomposite, FTIR, TGA, RMS, FESEM, oxygen permeation analysis was used in the films produced and contact angle measurements.

FTIR Analysis revealed that the modification of the diamond nanoparticles with the silane agent was well performed. FESEM images show that homogeneous nanocomposites were created. Oxygen permeability in polyvinyl acetate / diamond nanocomposite film decreases with increasing percentage of modified nanoparticles in nanocomposite. This is a valuable property if this nanocomposite is used as a fruit preservative coating. Contact angle measurement of polyvinyl acetate / diamond nanocomposite showed that by increasing the amount of modified diamond nanoparticles from 0.5 to 2 wt %, the hydrophobicity of nanocomposite film increased. Therefore, by increasing the specific amount of nanoparticles to the polymer matrix, the polymer properties such as heat resistance and tensile strength are increased which increases the efficiency of the polymer.