Sharif Digital Repository

In this project, modification of reverse osmosis membrane was investigated in order to reduce the biofouling in treatment of brackish water. Furthermore, the technique which is used to attain the favorable results is graft polymerization to modify the membrane’s surface with grafting acrylic acid as hydrophilic monomer onto polyamide exploited as last layer in reverse osmosis membrane. This technique is a free radical grafting, andfree radicals which are needed for grafting are provided by the redox system potassium persulfate-sodium metabisulfite which was used as initiator. To figure out the best concentration of acrylic acid, initiator and process time in order to achieve a new membrane... 

This thesis focuses on the preparation and super-swelling behavior of four highly porous hydrogels: 1. Firstly, we have developed a collagen-based highly porous hydrogel by neutralizing the grafted poly(acrylamide-co-acrylic acid) after gel formation. Systematically, the certain variables of the graft copolymerization were optimized to achieve maximum swelling capacity. Morphology of the samples was examined by scanning electron microscopy (SEM) and was shown the pores were induced into the hydrogel by water evaporation resulting from neutralization process. The absorbency under load (AUL) and centrifuge retention capacity (CRC) were measured. The synthesized hydrogel exhibited a... 

The high rate of energy consumption in the building sector has led the designers towards the construction methods that consume less energy during construction up to serviceability. One of these methods is rammed-earth (RE) structures due to the availability of its materials, ease of preparation, considerable decrease in energy consumption and environmentally-destructive consequences. Improving the thermal characteristics besides the mechanical parameters of RE structures develops the application of this method. In the current study, the dynamic thermal parameters of RE wall specimens were experimentally measured under simulated conditions and compared to those of masonry walls. Thereby, a... 

Today reverse osmosis (RO) is the dominant technology for desalination. Most of commercially available RO membranes are polyamide thin film composite (TFC) types which exhibit good performance. However, the major obstacle for application of polyamide TFC RO membranes is fouling which can be mitigate by surface modification.In this research, surface modification of fabricated aromatic polyamide TFC RO membranes was carried out using UV-initiated graft polymerization at different irradiation times (15, 30, 60, and 90 s) and various acrylamide concentrations (10, 20, and 30 g/L). Also, coating of membranes surface with various concentrations of TiO2 nanoparticles (10, 20, 30, and 50 ppm)... 

The use of super-swelling polymers is steadily increasing and the applications in industry are continuing to grow. With the authorization of the superabsorbents in food packaging by the Food and Drug Administration recently, demand may soon take off in the market. The worldwide production of SAPs is more than one million tons per year, representing a multibillion-dollar market. However, the increase in prices of petroleum products in recent years may be a drawback for these acrylic-based materials. Thus, there is now a need to develop natural-based super-swelling hydrogels which are more economical and environment friendly. In addition, the super-swelling gels are promising novel functions... 

In the present study, the acrylated polyurethane/nanohydroxyapatite (APU/n-HAp) nanocomposites were fabricated for use in bone tissue regeneration. The APU was synthesized based on poly(ε-caprolactone) diol (PCL), aliphatic 1,6- hexamethylene diisocyanate (HDI) and hydroxyethyl methyl acrylate (HEMA). The effect of HAp nanoparticles on the physicochemical properties of APU was evaluated. The APU/n-HAp nanocomposites were characterized using X-ray diffraction (XRD), dynamic mechanical thermal analyses (DMTA), scanning electron microscopy (SEM) and mechanical tests including tensile strength and elongation at break. The increase in physical properties achieved by incorporation of n-HAp... 

Bio-based shape memory polymers with fast-response have high potential for use in medical applications. In this study, biocompatible and biodegradable nanocomposites based on shape memory polyurethane acrylates (SMPUA)/cellulose nanocrystals (CNC), were synthesized by in-situ polymerization. CNC is a natural and renewable nanoparticle that has been considered for medical applications due to its excellent mechanical and biological properties and surface chemistry. At the first phase of this study, in order to synthesize UV-curable shape memory polyurethane acrylate, polycaprolactone diol (PCL-Diol), hexamethylene diisocyanate (HDI) and hydroxyethyl methacrylate (HEMA) were used as an reactive... 

Smart bio-based shape memory polymers with high performance and fast response have the exciting potential to meet the growing need in biomedical applications. A fascinating approach in SMP categories in biomedical field is the development of noncontact activation without increasing the environmental temperature through remote triggering methods, such as magnetic triggering. Magnetically responsive SMPs have received lots of attention in the biomedical applications, especially the non-contact triggering of medical equipment and implants inside the body. In this study, the biocompatible nanocomposite based on shape memory polyurethane acrylates (SMPUAs)/ hybrid carbon-magnetic nanoparticles,... 

Shape memory polymers have the potential to use in the field of biomedical applications. In this research, polyurethane structures have been synthesized based on the Diol mixtures, consisting of polycaprolactane diol (PCL-diol) and poly (lactic acid) diol (PLA-diol). Aim of reasearch is about evaluating poly (lactic acid) effect in structure of the polyurethane. At the same time, cellulose nanocrystals (CNC) have been added to polymer matrix to improve properties. The synthesis of acrylated polyurethane, included the synthesis of polyurethane acrylate prepolymer. Next, this prepolymer has been cured by adding the reactive diluent and some polyol. The cured systems were investigated, finally,... 

The natural tissue of the bones consists of organic and inorganic parts. The bone mineral part contains calcium phosphate and its organic part is mainly of collagen fibers. The combination of these fibers and calcium phosphate makes the bone flexible and resistant to stresses. Many conditions, including osteoporosis and crashes, lead to fractures and cavities in bone. Bone cements are the most used materials used in orthopedic surgeries and spinal cord.The purpose of this study was to synthesis acrylic bone cement with properties determined by ASTM F 451 and Iso5833 for orthopedic applications, including joint replacement. Polymethyl methacrylate polymer was synthesized as the main component... 

In this thesis, a novel graphene oxide (GO)/sodium alginate (SA)/polyacrylamide (PAM) ternary nanocomposite hydrogel with excellent mechanical performance has been fabricated through freeradical polymerization of acrylamide (AAm) and SA in the presence of GO in an aqueous system followed with ionically crosslinking of calcium ions. Physical and chemical characteristics of the composite were investigated by Fourier transform infrared spectroscopy and scanning electron microscopy. The swelling behaviors of the composite hydrogels were investigated under varying conditions of time and pH. The optimized swelling capacity in standard conditions was found to be 1711% per gram of the hydrogel. The... 

In recent year's acrylamide as a suspected substance for tumor growth has been studied. In some researches this topic is mentioned that acrylamide is produced by the reaction of asparagine and natural sugars. This reaction takes place only at very high temperatures during the heating process. The maximum amount of this substance is determined in fried potato products. In this study, a response surface methodology (RSM) 5-level-3-factor face centre central-composite design (FCCCD) was applied to envestigate the effects of asparaginase (300-900 U/kg of flour), baking temperature (230-280 °c) and baking time (13-16 min) on acrylamide (AA) formation in yeast-leavened wheat bread and... 

Nowadays, water pollution and water sources decreasion, is one of the important issues of our world. Treatment of polluted water and wastewater and recycling of those to industries and common uses, is very necessary. Dyes, is one of the biggest parts of water pollutants, especially, in textile plants. There are some ways for dye removal, in the industries; including biological, chemical and physical methods. Among of these methods, physical removal of dyes through adsorption (with Activated Carbon or other adsorbents), is very popular. Hydrogels are three-dimensional hydrophilic polymer networks, introducing very good swelling rate, mechanical properties and pollutants adsorption. In this... 

Composite membranes are one of the promising membranes for overcoming the limitations of conventional membranes in gas separation application by improving the permeability and selectivity. However, it is still very challenging to achieve adhesion interface between the top selective layer and the bottom support layer. The present study demonstrates that this challenge can be overcome appropriately by utilizing a series of adhesive polymer as selective layer to prepare composite membrane. To this end, in the first section a series of acrylate-terminated polyurethanes (APUs) based on poly(ethylene glycol) (PEG) with different molecular weights (Mn) of 600, 1000, 1500, 2000 and 4000 g/mol,... 

This thesis focuses on the preparation and super-swelling behavior of a superabsorbent hydrogel based on natural macro-molecules and loading potassium nitrite as an agro-chemical onto it. 1-In this investigation a new type of superabsorbent hydrogel based on Gelatin and k-Carrageenan was prepared and the effect of the feed ratio of some components (acrylic acid, MBA, APS, and agar) on the swelling capacity of the hydrogel was systematically studied. The structure of the hydrogel optimized final product was found to be 1064 g/g in distilled water. The structure of the hydrogel was characterized by FT_IR method and morphology of the samples was examined by scamming electron microscopy (SEM).... 

This thesis focouses on the preparation and super-swelling behavior of two superabsorbent hydrogel. In the first section, a new superabsorbent hydrogel based on agar was prepared and the effect of the ratio of some components(AA, AAM, MBA, APS and agar) on the swelling capasity of the hydrogel was studied. Maximum water absorbency of the optimized final product was found to be 614.5 g/g in distilled water. The structure of the hydrogel was characterized by FT-IR method and morphology of the samples was examined by scanning electron microscopy(SEM). Swelling behavior properties of optimized hydrogel sample in different swelling medium were investigated. In the second section, we report the... 

In recent year's acrylamide as a suspected substance for tumor growth has been studied. In some researches this topic is mentioned that acrylamide is produced by the reaction of asparagine and natural sugars. This reaction takes place only at very high temperatures during the heating process. The maximum amount of this substance is determined in fried potato products. The purpose of this study was determined to remove and reduce acrylamide formation during frying of potato. Acrylamide production when it was blanching and when it was dipped in the enzyme solution of asparaginase was examined. When potato pieces were placed in a commercial enzyme solution 200 lU/ml, acrylamide formation was... 

L-asparaginase enzyme is a well known enzyme due to itschemotherapeutic properties. However, this is not the only feature of the enzyme. L- asparaginase can be also used in food processing to reduce of acrylamide which is a carcinogenic substance. furthermore, acrylamide formation, is prevented by addition of the enzyme before cooking process of some foods such as chips, which contains sugar and asparagine amino acid. Due to use of the enzyme in food industry, we need to produce enzyme with high activity and cheaper raw material. In the present study, Candida utilis ATCC 9950 was used to produce asparaginase enzyme, and beet molasses and yeast extract was used as a carbohydrate and... 

Atom transfer radical polymerization (ATRP) is a convenient approach to synthesis of polymer with narrow molecular weight distribution. ATRP of acrylamide (AAm) is taken into consideration because of the intrinsic properties of acrylamide such as water solubility and biocompatibility. As reported in many recent works, polymerization of acrylamide by this method didn’t provide monomodal molecular weight distributions. In best condition with strong ligands such as Me4Cyclam, polymerization was carried out in a short time with high yield but polymerization was not highly controlled. It was shown that polymerization of acrylamide under typical ATRP condition displayed a much lower ATRP... 

Plants and aquatic creatures growth on the surface of human made structures is a typical phenomena. One of the approaches to prevent algae and moss to grow is using paint coatings including biocides. In this research project, anti-moss paints containing Copper Oxide as the major biocide and Zinc Oxide as the minor biocide have been synthesized. The effects of different parameters like the type of resin, biocide concentration, biocide grain sizes, dip time, and the coating layer thickness on the release rate which is the most important factor to prevent moss growth, have been investigated. Then, the experiment has been conducted on the specimens in algae growth and flustered sea water...