Sharif Digital Repository

Plasticizers in cementitious systems are additives that upon addition at a low dosage can change the workability, mechanical strength and other properties of cement paste effectively. In this study, tri-block copolymers based on poly ethylene glycol (PEG) was synthesised and their applications in the cementitious systems investigated. The main purpose is the verification of plasticizing effects of these copolymers in the cement paste. ABA tri-block copolymers with PEG (1000 and 1500 g/mol) as B block, poly caprolactone, poly caprolactam, poly lactide and poly glycolide (with different weight ratio) as A block were synthesised via ring opening polymerization with stannous octanoate as... 

Polypropylene block copolymer is used in different industries like pipe productions. This copolymer has proper mechanical properties, specially it has good impact strength, but in some applications it’s elastic modulus (stiffness) is not enough and that leads to some problemes in servise. Nucleating agents influence crystalline structure and properties and also the mechanical properties by controlling the crystallization process. Nanoparticles also have a beneficial effects on physical and mechanical properties. In this study, the effect of adding two types of α-phase nucleating agents (commercial names NA11 and DMDBS) in the form of masterbatch wt 5% with a carrier of polypropylene block... 

In today’s world the growth in population make food production and also the packaging industry increase. Finding new ways to enhance the efficiency of packaging is become so important beyond researchers. As the randomized co-polypropylene is the most suitable materials for this industry many attempts have been made to control its melting behavior with the aim of expanding their application in the packaging industry. The study in this field indicate the dependence of the melting behavior on the structural characteristics of the material such as molecular mass, chain structure, type of crystalline structure, and the amount of dispersion of the crystals thickness. Due to the lack of proper... 

Polypropylene (PP) is one of the most widely used commercial plastics in various industrial applications due to its desirable physical and mechanical properties and low cost. Engineering properties of this polymer depend very much on its crystalline structure. It is a common practice in polymer industry to modify crystalline structure by means of nucleating agents. Since nucleating agents are added in a rather low level to polymers, some investigators have tried this task in modifying crystalline structure of polypropylene by incorporating nucleating agent masterbatches. However, none have looked at the possible influence of the carrier resin in such masterbatches on the performance of... 

Today, current methods are used for treatment of cancers. Patient experiences a period of hard treatment during destruction of both healthy and diseased cells. Researchers are following stimulus- response drug delivery systems that they control time and position of drug release. Meanwhile, micellar nanoparticles are important, because it can transport the hydrophobic anticancer drugs from body's physiological barriers. On the other hand, tumour tissue has low pH and high temperature as compared to health tissue. Therefore, using pH and thermosensitive polymer coating could be effective in triggered drug release. In the first study, micellar systems were synthesized which were responsive to... 

Ethylene vinyl acetate copolymer produces flexible products and is compatible with many polymers and additives, the reason is that it has Vinyl group which is polar and Ethylene group which is nonpolar. In fact, it consists of two parts. One is a hard and semi-crystalline Polyethylene region and the other is soft, flexible, polar, and amorphous Vinyl Acetate. Improving the properties of this copolymer can broaden its application. For this purpose, Ethylene Vinyl Acetate with 18 and 28% Vinyl Acetate was used as a matrix and nano-alumina as reinforcement in this project. The spherical structure and chemicallu active surface, along with significant mechanical properties, suggeats Alumina... 

With the decline in oil discoveries during the last decades, it is believed that enhanced oil recovery (EOR) technologies will play a key role to meet the energy demand in coming years. Polymer flooding has been commonly used worldwide as one of the EOR processes. Literature reviews show that the active water-soluble polymers have a number of limitations related to their surface absorption, undesirable plugging, polymer concentration limitation,expensive, and low thermal, mechanical, bacterial, and salt tolerance. Up to now, five different polymer categories (i.e. polyacrylamide, hydrolyzed polyacrylamide, acrylamidebased resistant copolymers, associative copolymers, and thermoassociative... 

Propylene Copolymers and terpolymers with small amount of 1-butene& ethylene can greatly improve the properties of polypropylene material such as low temperature toughness, printing performance, transparency, process ability and so on, leading to expanding of its application. Poly(propylene-co-1-butene) performance intensely relies on its composition and chain structure. The copolymerization catalyzed by Ziegler-Natta catalyst, which is a multy-active central system. The Ziegler-Natta catalyst TiCl4/ Mg(OEt)2/ DIBP was used for copolymerization. The microstructure of copolymers were characterized by FTIR. The influence of different comonomer ratios on the copolymerization has been... 

This study has concentrated on preparation of mixed matrix membranes (MMMs) in order to improve the separation performance of the neat poly(amide-12-b-ethylene oxide)(Pebax1074) membrane. Pebax1074 and zeolite SAPO-34 were used to fabricate MMM for the first time. Micro-size SAPO-34 was added to polymer matrix up to 35wt% based on polymer weight; even though at this high loading percentage the prepared membranes were not stable enough to be tested for characterization and gas permeation. The obtained results showed more than 30% increment in CO2 permeability, along with slight growth and reduction in N2 and CH4 permeabilities, respectively for 30wt% zeolite content membranes. Permeability... 

In recent years, mesoporous nanocrystalline TiO2 films have been regarded extensively. This kind of materials due to having unique surface area, structural and bulk properties, is used in many technological applications. In this work, a stable TiO2 sol was prepared using F127 Copolymer template and evaporation induced self-assembly method (EISA). The mesoporous TiO2 powders and thin films were then prepared. The as-deposited thin films were aged under five different conditions for 72h. Finally the samples were heat treated at 350°C, 400°C and 450°C. N2 adsorption/desorption results verified formation of mesoporous structure. Moreover, x-Ray diffraction patterns exhibited that the synthesized... 

Acidic gases separation from hydrocarbon mixtures is very important in natural gas industry. In this study, the separation of CO2 and H2S from CH4 investigates by experimental and molecular dynamics simulation approaches. For achievement to this goal, it is used two polymeric families, as be divided to polyurethanes and PEBAX copolymers. It is used 4 polyurethane membranes as are named PU-1, PU-2, PU-Ether, and PU-Ester from polyurethanes group. Also, it is applied 5 PEBAX commercial membranes have be known PEBAX-2533, PEBAX-4033, PEBAX-5533, PEBAX-4011, and PEBAX-1074. It is compared between simulation and experimental works and found that there is good agreement between... 

The present work investigates a novel approach for improving the oxygen-barrier property of PLA-based film using vinyl acetate-vinyl alcohol copolymer [Poly(VAc-co-VA)] and the nanoclay Nanolin DK4. The permeability, thermal and mechanical properties are studied. To synthesize poly(VAc-co-VA), the hydrolysis of PVAc was done. The nanocomposite blend of PLA/Poly(VAc-co-VA)/Nanolin DK4 was prepared by the solution casting method. The prepared nanocomposite films were optically transparent regardless of poly(Vac-co-VA) and Nanolin DK4 concentrations. The gamma irradiated Poly(VAc-co-VA) was incorporated in the PLA films to probe the effect of cross-linked copolymer on the permeability of the... 

In this project an enzymatic peroxidase biosensor based on two naono structured material 1-Polyaniline nananofibers 2-Polyethylene glycol-Poly citric acid copolymer was studied for phenol detection.Polyaniline nanofibers and poly ethylene glycol-poly citric acid copolymer were synthetized by chemical polymerization.Electrochemical behaviors of these biosensors were studied using cyclic voltammetry (CV) and amperometric techniques. The amperometric response of the coated electrodes is highly stable with 92% of the initial activity remaining after 5 determinations. These phenol biosensors show an oxidation peak at 0.55V. The amperometric response for phenol biosensor based on Polyaniline... 

In this research, polypropylene and propylene- ethylene copolymers were synthesized and propylene- ethylene copolymer Graphene Oxide Nano composites were prepared via solution mixing method. Nano Graphene Oxide sheets were synthesized utilizing modified hummer’s method. Ziegler Natta catalyst system was a complex of Magnesium Ethoxide as the support of the catalyst and Titanium tetra Chloride as the catalyst. Tri iso Butyl Aluminum (TiBA) and Tri Ethyl Aluminum (TEAl) were used as co catalyst. FT-IR and XRD patterns show well oxidation of graphite sheets and fragmentations of them. FESEM images clear the successfulness of copolymerization and also well-dispersion and distribution of Nano... 

Phenolic compounds, which are one of the most dangerous compounds for the environment, are present in many effluents of various industries such as petrochemicals and pharmaceuticals, and the need to eliminate these compounds is increasingly felt. In this study, adsorption of three compounds of para-chlorophenol, para-nitrophenol and hydroquinone on polypyrrole adsorbent in the form of neutral, charged, copolymer with polyaniline and phosphorus-doped have been investigated using density functional theory (DFT). Calculations are performed at two levels of b3lyp/6-31+G(d,p) and wb97xd/631+G(d,p) for two different orientations of adsorbate molecules that the correlation-exchange function wb97xd... 

Today, incremental manufacturing processes are rapidly evolving and expanding. These processes are used for the rapid fabrication of prototypes as well as the fabrication of parts with high geometric complexity and high dimensional accuracy. These processes are used in various fields such as manufacturing industrial parts, medicine, precision casting, etc. One of the most important incremental manufacturing processes that has received much attention today is the selective laser processing process. One of the problems of this process is the limitation in the use of different polymers for processing. Polyamide 12 currently has about 90% market share due to its high processability. However,... 

With the rapid increase of energy consumption, energy problem has been a global issue, which must be faced with and solved. One way to prevent energy consumption is to reduce drag in the flow inside the pipes by using polymer additives; Because the Transportation of liquids using pipeline technology has its limitations, since turbulent flow inside the pipe involves a loss of energy. The net effect of this is that increasing the energy applied to the flow does not increase the flow rate. For this purpose, copolymers and terpolymers of hydrophilic acrylamide monomers along with hydrophobic styrene and hydrophilic maleic anhydride monomers were synthesized by reverse emulsion polymerization... 

to achieve a stable elimination of colloidal suspended particles, polymer flocculants such as polyacrylamide and its derivative have been more used. To improve the performance of removing turbidity, reducing settling time, and better dewatering from sediments, hydrophobic styrene monomer copolymerized with acrylamide monomer. In this study the copolymer of acrylamide and styrene was synthesized by inverse emulsion polymerization, then this copolymer undergoes hydrolysis to form anionic groups on the polymer backbone. FT-IR, H NMR, and TGA analyses were carried out to investigate the structure of the copolymer. To evaluate flocculation, turbidity tests, zeta potential, and sedimentation rate... 

The use of polymers in the EOR process is very common. Most of these polymers are sensitivity to temperature, salt, and the presence of bacteria. Among these materials, hydrolyzed polyacrylamide (HPAM) is the most widely used. Due to the sensitivity of HPAM in harsh conditions like temperature and salinity of the environment, modification of this polymer by hydrophobic groups can be very effective. Hydrophobic-hydrophilic associative polymers have shown unique rheological properties and high thermal stability, which is due to the presence of a small percentage (up to two percent) of hydrophobic monomers in their structure. Despite these excellent properties for acrylamide copolymers...