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Showing 13 results for Polymerization


Volume 3, Issue 4 (3-2020)
Abstract

Research subject: Parkinson’s disease is a neurodegnerative disorder with no treatment due to the blood brain barrier (BBB) existence. The cure for this disease is Dopamine a chemical molecule.
Research approach: This study investigates biodegradable naoparticles (NPs) carrying dopamine (DA) across the blood–brain barrier. Ion polymerization and solvent methods were used to achieve this goal. Particle size, zeta potential, entrapment efficiency and in vitro drug release behavior, at pH 7 were examined.
Main results: The empty nanoparticles and drug-loaded nanoparticles were found to be spherical in shape and fluffy exterior, with mono-modal size distribution and negative zeta-potentials of increasing average sizes 90 to 120 nm simultaneously. Fourier transform infrared (FTIR) spectra demonstrated the polymerization of nBCA monomers and encapsulation of DA inside poly (butylcyanoacrylate) (PBCA).Thermal characteristics of the copolymer were investigated by Fourier-transform infrared spectroscopy (FTIR). Drug loading efficiency was around 25%.The in-vitro drug release profile of DA -loaded PBCA nanoparticles prepared from ion polymerization following solution techniques exhibited a gradual release; more than 20 ٪w/w of the drug was released after 51 h. The results showed that the DA–PBCA nanocapsules could be an effective carrier for hydrophilic agents. In this study, PBCA-NSPs were successfully generated as a delivery system for DA, providing a promising approach to improve the therapy of PDs.

 
 

Volume 5, Issue 2 (9-2021)
Abstract

Research subject: Expandable Poly Styrene (EPS) has many applications. This polymer prepared by the radical polymerization. This material has many uses in packaging and insulation industries Some of the properties of this polymer like low mechanical strength caused its applications to be limited. By adding some materials, these properties can be improved. Styrene Butadiene Styrene (SBS) is from the materials that which by adding it to the EPS it can improve its quality.
Research approach: In this research, EPS having different percentages of SBS (0, 0.01, 0.02, 0.03) in different conversion percentages (0.6, 0.63, 0.66, 0.69) has been prepared. Different tests like Impact Test, Modular Melt Flow test, Vicat Softening Temperature test, Tensile at Break test, K-value test, Rochwell Hardness test and Elongation at Break test are done on the prepared polymer. Laboratory gained data has been simulated by Multi-Layer Perceptron (MLP) method of artificial neural networks (ANN) and the simulated data covers the laboratory data perfectly.
Main Results: Investigating the tests show that in constant percentages of SBS in EPS with increase in conversion percentage of EPS, the numerical amount of the tests increases except MFI test (low MFI number means better quality). Increase in SBS percentage in the EPS, increases the properties of polymer. In addition, the results of simulation show that the laboratory data covers the the simulated data perfectly. The data obtained from the results of this reasearch can be used for predicting the data for the points which has not been tested. Adding SBS in different weight percentages of poly styrene in different conversion percentages in order to increase the properties of poly styrene has been used for the first time in this research and the laboratory data results in points which has not been tested has been acquired by applications of ANN.

Volume 6, Issue 1 (6-2022)
Abstract

Abstract
Research subject: In recent years, toner-based printers have found many applications for ease of use, economical, high speed and quality. Therefore, many attempts have been made to produce toner by various methods such as suspension polymerization and emulsion aggregation. But in all these methods, despite the proper color properties and particle size, the reaction conversion is low.
Research approach: In the present study, in situ emulsion polymerization method based on styrene and butyl acrylate monomers in the presence of carbon black has been used to produce toner with a conversion above 75%. In this regard, the effect of polymerization reaction temperature and stirrer speed on conversion at different times, particle size and particle size distribution, thermal and color properties of the final product were investigated. Color measurement was performed to evaluate the color characteristics. Also, the microstructure of the synthesized toners was evaluated using scanning electron microscopy.
Main results: The results show that in situ emulsion polymerization method while having the proper conversion of the reaction in the range of 75-90% is well able to create the suitable color characteristics and particle size distribution for the toner. All toners produced had a particle size distribution and a spherical shape that was unaffected by the reaction temperature and stirrer speed. By increasing the polymerization temperature from 70℃ to 80℃, resulted in a higher conversion, but the increase in stirrer speed had a dual effect on the conversion. Sticking of spherical particles with each other was observed by increasing the temperature to 90℃. The sudden addition of a monomers to the reaction media and using batch process resulted in the observation of two glass transition temperatures. This type of toner synthesis can be a guide for future research to produce toner with the highest conversion.


Volume 7, Issue 1 (7-2023)
Abstract

Research subject: The binder system based on of hydroxyl-terminated polybutadiene resin (HTPB), consist of dioctyl sebacate as a plasticizer (DOS), and toluene diisocyanate as the curing agent. Reaction between the HTPB hydroxyl resin group and the curing agent isocyanate group produces a polyurethane mesh to produce a rubber with the desired properties. In this research, the rheological and mechanical properties of the binder system were investigated and Physical properties compared in the presence of three chemicals retarder polymerization Polyurethane, oxalic acid, maleic acid and tetracycline.
Research approach: Oxalic acid, maleic acid and tetracycline alter the properties of the binder system by specific mechanisms. Oxalic acid and maleic acid react with the isocyanate group of the curing agent to produce amides and reduce the viscosity of the binder system. Due to its chemical structure, tetracycline reacts with the curing agent and prevents the development of the main reaction between the HTPB resin and the curing agent TDI and reduces the viscosity. Infrared Fourier transform (FT-IR) test was also used to investigate the functional mechanism of these compounds. In this test, the intensities of the spectra related to each sample were compared with each other and the type of function and mechanism of each of the oxalic and maleic substances and tetracycline were determined.
Main results: The structure of the reaction product between HTPB resin and oxalic acid, maleic acid and tetracycline with curing agent was determined and confirmed by FT-IR spectrum. In-situ FT-IR study showed reduction in isocyanate peak intensity after 60/90 min. Chemorheological investigation showed best performance at 0.05% concentration for all retardants, among them tetracycline, oxalic acid and maleic acid depicted 54%, 48% and 47% reduction in viscosity build-up; respectively. Adding 0.05% of tetracycline to binder system resulted in about 20% decrease in cross link density probably due to better interaction with curing agent which emphasized the best performance of 0.05%-tetracycline as retardant.
 
Seyedeh Maryam Hosseini, Sadegh Hasannia, Bijan Ranjbar,
Volume 11, Issue 3 (10-2020)
Abstract

Human alpha1-antitrypsin is a glycoprotein comprised of 394 amino acids and 52 kDa molecular weight, which is mostly synthesized and secreted by hepatocytes, diffuses to interstitial lung tissues, and has an essential function to protected tissues against neutrophil elastase. One of the significant challenges in dealing with alpha-1-antitrypsin is the structural instability of the folded form of protein and, consequently, the accumulation of polymers in lung tissue. This makes patients vulnerable to chronic obstructive pulmonary disease, severe asthma, and emphysema. Intravenous augmentation therapy of alpha 1-antitrypsin is one of the most prevalent therapies. Moreover, patients who are candidates for that have respiratory symptoms, and the use of bronchodilator (Salbutamol) is the first recommended standard treatment. In this study, protein purification was performed by using high-performance affinity chromatography and, its purity was confirmed by gel electrophoresis.  The effect of different concentrations of salbutamol on heat-induced polymerization at 60 ° C was investigated by non-denaturing polyacrylamide gel electrophoresis, dynamic light scattering (DLS), and circular dichroism (CD) techniques. Protein activity was measured by trypsin inhibitor capacity (TIC) assay. The results indicated that salbutamol decreases the rate of polymerization by reducing the flexibility of the reactive center loop, thus decelerate protein activity reduction. Therefore, salbutamol can be an appropriate supplementary for alpha 1-antitrypsin and a proper option for the treatment of protein polymerization associated diseases.

Volume 16, Issue 4 (7-2014)
Abstract

The aim of this study was to investigate the effect of steam treatment on nutritive value of date (Phoenix dactylifera) leaves. Date leaves were chopped and mixed with water or sulfuric acid solution to contain 50% moisture with or without 1% sulfuric acid. Steam treatment of the date leaves was carried out using three levels of steam pressure (14, 17 and 20 bar), three reaction times (120, 180, and 240 seconds) and two levels of acid (0 and 1 percent). The treated samples were analyzed for chemical composition including: cell wall components, ash, total extractable phenolics, water soluble sugars, and reducing sugars. Dry matter loss (DML), enzymic hydrolysis, and in vitro gas production of the samples were also measured. Results showed that steam treatment significantly affected (P< 0.05) cell wall components. An increasing trend was observed in DML by increasing harshness of treatment conditions. The lowest DML (12.7 g kg-1) was observed in the auto-hydrolyzed (steam treatment without addition of exogenous acid) sample treated at 14 bar pressure and 120 seconds reaction time and the highest DML (78.8 g kg-1) was observed in the acid-hydrolyzed (addition of 10 g kg-1acid prior to treatment) samples treated at 20 bar pressure and 180 and 240 seconds reaction times. Steam treatment significantly (P< 0.05) decreased neutral detergent fiber (NDF) content but increased acid detergent lignin (ADL). Maximum changes in hemicellulose and water soluble sugars were observed in acid-hydrolyzed samples, in which hemicellulose decreased from 264.6 g kg-1 in control to 72.2 g kg-1 in the sample treated at 20 bar and 240 seconds and water soluble sugars increased from 14.0 g kg-1 in the control to 101.8 g kg-1 in the sample treated at 17 bar and 240 seconds. Enzymic hydrolysis of date leaves was improved after steam treatment and higher improvement was observed in acid-hydrolyzed samples. Gas production was significantly increased (P< 0.05) in all incubation times after steam treatment. The maximum increase in metabolizable energy (ME) estimated by gas production was from acid-hydrolyzed sample treated at 20 bar and 240 seconds. In auto-hydrolyzed samples, the biggest increase in ME was observed in the sample treated at 20 bar and 180 seconds. The results suggest that steam treatment could be used for upgrading the nutritive value of date leaves in the regions where date is grown and animals are encountered with severe feed shortage.

Volume 18, Issue 118 (12-2021)
Abstract

This study was aimed to investigate the effect of Maillard reaction polymerization degree (PD) on functional properties of whey protein isolate. The whey protein isolate-gellan gum conjugate was synthesized by the Maillard reaction and the intermediate-to-final products absorption ratio (A294nm/A420nm), as the index of Maillard reaction PD, was evaluated. The whey protein isolate-gellan gum conjugates were then classified into three low, medium, and high PD using K-means clustering method, and their interfacial activity (interfacial tension reduction ability, emulsifying activity, and emulsion stability) and surface activity (foaming capacity and foam stability) were investigated. Interfacial tension at oil/water interface was reduced more efficiently by the medium PD whey protein isolate-gellan conjugate, indicating its higher adsorption rate to the interface (higher emulsifying activity), ability to form a viscoelastic thick layer at interface, and consequently increase the emulsion stability through steric repulsion. Although, foaming capacity was not significantly influenced by the PD (p>0.05), the foam stability in the presence of medium PD conjugate was significantly higher than the foams stabilized by other conjugates (p<0.05). Therefore, a medium PD is needed to improve the functional properties of whey protein and increase its industrial applications.

Volume 18, Issue 120 (12-2021)
Abstract

Vitamin B3 (Nicotinamide) is involved in many vital reactions in the human body as the precursor of NAD and NADP. NAM deficiency can lead to pellagra thus foods are fortified with this vitamin. On the other hand, high intakes of NAM can cause some symptoms.  Hence, a cheap, rapid, selective and sensitive determination of NAM concentration in foods is crucial. The present study propose a NAM analysis method for beef and wheat flour by employing a molecularly imprinted polymer based solid phase extraction clean-up coupled with HPLC-UV. Precipitating polymerization technique for fabrication of NAM molecularly imprinted microspheres was utilized. The effects of polymer ingredients including functional monomer, cross-linker monomers, template and solvent were investigated on binding characteristics.The binding behaviour of the polymer well modeled through Freundlich equation and the polymer showed high selectivity of NAM over nicotinic acid (NA). In a kinetic study, 79% of NAM binding and 96.5% of NAM release occurred immediately. The NAM imprinted microspheres were packed into SPE for NAM extraction, food samples injected and the output analysed with HPLC-UV. Good linearity was obtained for solid phase extraction of NAM in the range 148–5000 μg L-1 (R2 = 0.999) and high extraction recoveries of 77–102% and 81–87% were obtained for NAM in beef and wheat flour samples, respectively. The limit of detection (LOD) and limit of quantification (LOQ) for nicotinamide  were 44 μg L-1 and 148 μg L-1, respectively. The overall inter-day and intra-day relative standard deviations of  2.13% to 5.31% for wheat flour (n=4), and 1.89% to 5.22% for beef samples were obtained, demonstrating good precision of the proposed method in its application for real sample analysis.

Volume 19, Issue 3 (5-2017)
Abstract

This experiment was conducted to determine the potential synergistic relationship between Enterococcus faecium and fructans with different average Degree of Polymerization (DPav) including OligoFructose (OF, DPav 4), Standard-inulin (ST-inulin, DPav 10), Synergy1-Inulin (SYN1-inulin, DPav 15) and High-Polymer inulin (HP-inulin, DPav 25). A sterilized minimal MRS broth media was prepared by omission of glucose. The media pH was adjusted to a constant initial value of 5.8±0.1 and the temperature was maintained at 41°C. Sterilized fructans were added (1% wt⁄vol) to the broths, as experimental treatments with 3 replications each, and the medium with no added prebiotic was considered as the control. The same starting density of 108 E. faecium cells per ml was introduced to all media. The media pH, viable cells count, as well as growth of the latter were determined during 24 hours of incubation. The lowest pH and best growth rates were observed in the media enriched with OF and ST-inulin. Unlike aerobic, the anaerobic conditions produced no significant differences in growth of the bacteria among SYN1-inulin and HP-inulin treatments compared to the control. The viable cells count in the media containing OF was significantly higher than in the control and other treatments. The significant differences were also found among the control and treatments supplemented with ST-inulin and SYN1-inulin. In conclusion, the fructans with lower DP were preferentially metabolized by E. faecium, and hence it follows that a synbiotic blend of E. faecium and OF has the potential to be used in poultry nutrition.

Volume 20, Issue 144 (1-2024)
Abstract

Native starches have limited use in the food industry owing to their insolubility in cold water and lack of reactivity. Native starches are susceptible to chemical, physical, and enzymatic modification. This article examines cold plasma as one of the physical mechanisms of starch modification. The structure of each system is analyzed, and the effects of cold plasma at atmospheric pressure on the functional, thermal, molecular, morphological, and physicochemical aspects of various starches researched by different researchers are described. Changes in the characteristics of DBD plasma-modified starch are primarily caused by the depolymerization and cross-linking of amylose and amylopectin side chains. The molecular weight, viscosity, and gelatinization temperature decrease after DBD plasma treatment. The plasma etching of starch granules improves their surface energy and hydrophilicity. Cold plasma is an alternate approach for changing starch characteristics; it may be inferred.

Volume 23, Issue 3 (3-2023)
Abstract

The additive manufacturing system using the continuous liquid interface production (CLIP) method, which was designed and constructed by the researchers of this article, was utilized in this research to examine the impacts of the oxygen control area's thickness on the speed of producing parts. The main goal of this research is to produce porous parts 10 times faster compared to the digital light processing (DLP) method. However, it's crucial to look at the printing height, the part failure rate, as well as the part curing depth in order to achieve this speed increase. One of the most crucial factors affecting the aforementioned circumstances is undoubtedly the oxygen control zone. Therefore, two window-shaped (island and microchannel) special gas-permeable membranes were utilized as the bed of the liquid resin container to generate this zone. Furthermore, employing each of the aforementioned windows, parts with a porous and complex structure were manufactured and evaluated. The usage of an island-like container increased the duration of continuous printing by 107% before the separation force begins, reduced maximum separation force by 4.7 times, and increased the height of the printed component by 30%, according to the study's findings. It also improved the part's visual quality.
 


Volume 23, Issue 6 (11-2021)
Abstract

The two-spotted spider mite, Tetranychus urticae Koch, is a highly polyphagous pest that is considered a serious pest worldwide. Due to problems associated with chemical pesticides such as resistance to pesticides and environmental contamination, plant oils have been considered for use against mites’ control. However, their low solubility in water and phytotoxicity are the major constraints that limit their application. In this research, a developmental screening process was carried out on some commercial emulsifiers and stabilizers to obtain a safe acaricide from suitable vegetable oils including castor and soybean. Among eight emulsifiers, Nonylphenol Ethoxylate 6M (NPE6) had far more excellent emulsification ability and less phytotoxicity with some level of mite toxicity. Among vegetable oils, castor oil had greater toxicity in comparison with soybean oil. Also, Polyethylene Glycol 400 (PEG 400) had more thermal stability in the formulation. In the last step, the best ratios of NPE6, castor oil, and PEG 400 were evaluated for their toxicity, stability, and phytotoxicity. Finally, the ratios of 1:8:1 or 2:6:2 (NPE6: Castor oil: PEG 400) were found as the best end product that could be potent for use in a large scale rose greenhouse. Also, the efficacy of emulsifier-oil-stabilizer mixtures was investigated against T. urticae by two different methods. The results indicated that the petri dish test method caused overestimating in mortality rates compared to the standing leaf test method. New methods such as polymerization can show a new insight for pest control without chemical pesticides.

Volume 24, Issue 3 (7-2021)
Abstract

Myelination refers to the formation of the myelin sheath around axons to guarantee rapid action potential conduction and provide trophic support to axons. It is a highly orchestrated process, which occurs in a regulated and stepwise manner. During development, oligodendrocytes progenitor cells (OPCs) proliferate and migrate to the different areas of the central nervous system (CNS). These cells then differentiate to mature oligodendrocytes, which extend their process toward axons and wrap around them. Many studies have examined the intracellular signaling pathways underlying the myelination process. PI3K/Akt pathway is one of the critical regulators of the oligodendrocyte maturation and CNS myelination. The mammalian target of rapamycin (mTOR) is the main downstream target of the PI3K/Akt pathway and its role in oligodendrocyte differentiation and developmental myelination has been previously identified. Here we summarized the current knowledge of the mTOR signaling pathway during developmental myelination and possible applications in remyelination. Details of the intracellular signaling mechanisms that regulate myelination might provide insight into pharmacological approaches to manipulate this process to enhance therapeutic approaches toward remyelination in demyelinating disorders.

 

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