Sharif Digital Repository

Melt blending of polymers is a rather cheap and easy approach for obtaining new set of properties compared to synthesizing new polymeric materials. For the same reason, binary and ternary polyethylene blends are made to provide added value for different applications. Polyethylene blends are commonly composed of high density polyethylene (HDPE), low density polyethylene (LDPE) and linear low density polyethylene (LLDPE). Although the Mechanical and physical properties of polyethylene binary blends have been studied extensively, microstructure and mechanical properties of polyethylene ternary blends have been the subject of very few studies. In this work, samples with 40-60 Wt. % HDPE and... 

Supersonic intakes with mixed compression has an appropriate performance in the critical point, but in the subcritical performance, when inlet mass flow rate is reduced to a certain amount, a self-sustained instability occurs in the flow. In this case, instability appears in the form of shock waves system oscillation which is called Buzz phenomenon. An axisymmetric supersonic air intake with mixed compression which is designed for a Mach number of 2 has been investigated experimentally in order to study buzz frequency. The intake has been experimented in different Mach numbers, angles of attack and mass flow rates. Besides, the intake with wind tunnel wall has been modeled and analyzed in... 

This thesis is a part of national studies of “attractiveness analysis and strategy formulation of fuel cell technology in Iran" that was done during more than two years with the guidance of fuel cell steering committee. In this thesis, first of all the possibility of applying the technology strategy model of Arnold Hax in national level was investigated. For this purpose, with regard to the fuel cell technology specifications and status in the country, from the perspectives of national need to the technology, capabilities of technology in the country and new applications of technology, the technology strategy models of positioning school were studied and from the models of this approach,... 

Nowadays, with the increasing number of polyethylene terephthalate wastes, the issue of its recycling has become very important. Among the problems of polyethylene terephthalate recycling are its loss of crystallinity and mechanical properties. Recycled polyethylene terephthalate does not have the properties of new polyethylene terephthalate and using its mixture with other materials is an effective way to remove its waste from nature and return it to the production cycle. The aim of this study is to produce a mixture of recycled polyethylene terephthalate with polycarbonate and glass fibers with mechanical properties such as good impact strength, which ultimately leads to the production of... 

The biocompatibility and chemical stability of boron nitride nanomaterials surpass those of carbon nanomaterials. In addition, boron nitride nanomaterials share the same structure as graphene materials, making them a suitable replacement for graphene in biological applications. In this study, SKOV3 cancer cells were actively targeted using amine-functionalized boron nitride quantum dots that were covalently modified by CD133 antibody. Under the condition that they are not conjugated with antibody, these nanoparticles were also incorporated into the microfluidic device designed to image MCF7 cancer cells. These nanoparticles were produced via solvothermal synthesis in an organic solvent... 

The research of this work was divided into two parts. First, A novel fuorescence sensor based on fluorescence resonance energy transfer for the determination of captopril was developed. FITC molecules that are highly fluorescent in alkaline solution fluoresce weakly when they are adsorbed onto AuNP surfaces (based on affinity of AuNPs and isothiocyanate group on FITC) as a result of fluorescence resonance energy transfer. In the presence of captopril, FITC molecules are released from the AuNP surface in order to stronger affinity to AuNPs surface than FITC molecule (in order to thiol group in captopril) so the florescence intensity of FITC restore. This phenomenon was used for quantitative... 

Synthetic polymers have a high capacity to provide and manufacture the pieces used in tissue engineering. However, optimizing the biocompatibility, bioresorbableility and mechanical properties simultaneous with processability of material is complicated and requires a lot of effort at designing different parts of the system. On the other hand, due to existence of secondary bonds (such as metal-ligand coordination or hydrogen bond) supramolecular polymers are able to respond to some stimuli such as temperature, pH, or pressure, which is important in terms of dynamic nature of interaction between the living cells and the external matrix of cell. Recently there have been extensive studies on... 

The feasibility to fabricate Al/SiCp nano-composite with functionally graded structure (FG-Al/SiCp) via friction stir processing was studied successfully in this paper. The distribution of well-dispersed nano-SiCp got a range of 6mm×3mm on the cross-section of nano-composite. A compositionally graded structure of nano-SiCp in thickness direction of the 5083Al plate was obtained via four passes of FSP. The percentage of nano-SiCp over 15%, 9% and 5% was found at the depth of 1.0mm, 2.0mm and 3.0mm, under processed surface of 5083Al rolled plate, respectively. Results show that the microhardness of FG-Al/SiCp nano-composite can reach steady 46%, 34% and 15% higher than the one of the base... 

Recently, due to the increase of environmental concerns, a significant raise in applying films and packaging containers, pollution produced from petroleum-based plastics packaging and problems arising from the various methods of waste disposal, the researchers have concentrate to replace these materials with biodegradable ones. In this study, a nanocomposite based on alloy matrix of thermoplastic starch and polyethylene which is reinforced with different amounts of Montmorillonitenanoclay has been constructed by the extrusion process. Furthermore, in order to increase the compatibility between the polar and non-polar components in the group of samples, compatibilizer was used and its... 

Polypropylene/clay nanocomposites are considered as a group of widely used nanocomposites in industrial applications due to their desired properties, yet reasonable cost. However, dissimmilar chemical nature of polypropylene and clay do not allow perfect dispersion of silicate layeres in the matrix and thus restricts full advantages of these composites.An earlier investigation in this group considered solving this shortcoming through incorporation of PA6 as an intermediate phase to enhance clay platelets dispersion. The current project follows this route via studing the influence of molecular weight of the PP matrix, compatibilzer and the mixing procedure of the compound. To investigate the... 

Due to the negative effects of conventional plastics on the environment, especially in the packaging sector, extensive efforts have been put to replace these polymers with biodegradable polymers. Starch is one of the biodegradable polymers which has attracted a lot of attentions because of low cost and good process ability. Native starch has the form of granule and can be processed to a continuous phase after gelatinization in the presence of a plasticizer. The resulting material is a biodegradable plastic-like material called thermoplastic starch (TPS) which is processed using conventional technologies, but suffers from low mechanical properties and high hydrophilicity. Addition of... 

In the most cosmological models which already have putted forth, metric has a spherical symmetry; however, according to the galaxy’s shape is not a real approximation. In order to build a more acqurate model, by applying a particular conformal transformation on the static vacuum solution, we introduce a new metric which is axially symmetric and also it approaches to FLRW metric at space infinity. The cosmological model according to this metric has especial features;The solution we have found represent a spacetime which is axially symmetric although it leads to a spherically symmetric Einstein tensor. Therefore, we have found a solution of Einstein equations representing a spherically... 

This project aimed to fabricate the bone scaffolds with applying thermoplastic starch-based nano-biocomposites. The starting materials for this scaffold are as follows: thermoplastic starch, ethylene vinyl alcohol as the polymer matrix and nanoforsterite as the ceramic reinforcing phase. Furthermore, vitamin E was used as antioxidant for preserving starch against thermo-mechanical degradations. Likewise, 3D pore structure was developed using azo-dicarbonamide and water in injection moulding process. With blending thermoplastic starch and ethylene vinyl alcohol, some thermoplastic starch’s properties including degradation rate and water absorption were modified. In addition, having... 

Epoxy resins are relatively brittle and have low resistance to crack propagation. It is common to add rubber particles to improve crack resistance in epoxies, although these particles may deteriorate the strength of the matrix. Different nanomaterials are used to overcome the inherent brittleness of epoxies and to keep the mechanical properties. Among them, carbon nanotubes has been attracted many attentions. Fractue behavior and mechanical properties of two kind of novel nanocomposites, i.e, epoxy/carbon nanotube and epoxy/rubber/carbon nanotube are investigated in current study. Electron microscopy investigations were done to assure the CNTs distribution and fracture mechanisms as well.... 

Blend of Polycarbonate/ poly(butylene terephthalate) is among the most famous blends of polycarbonate/polyester with vast engineering applications and unique properties. Miscibility and compatibilization of this blend are important as they directly influence the general properties.Transesterification which occurs in the melt state, is a series of cutting and rejoining of dissimilar polymer chains. The reaction ruins the order of pure chains and forms block copolymers of different natures. Further progress in transesterification lead into a completely random copolymer of initial chains. Time, temperature and addition of catalyst can effectively influence transesterification.In this study,... 

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... 

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... 

Polyamide 6 is one of the well-known and oldest engineering thermoplastics, which has many uses in the transportation, automotive, apparel and sports industries due to its high strength, high corrosion resistance and high service temperatures. Cite gears, radiator tank, cylinder head cap and fuel rails can be mentioned as Polyamide 6 applications in the automotive industry. Glass fibers are used as reinforcement in PA6 media in order to enhance mechanical properties like tensile and impact strength. Even though the glass fiber improves the mechanical properties of the components produced from fiber-reinforced composites, it increases the anisotropy properties of the material and making it... 

Polyamide-6 is a thermoplastic polymer that is classified as electrically non-conductive materials. One way of adding conductivity to the polymer matrices is by utilizing them in a nanocomposite form. Superior mechanical and electrical properties of Carbon Nanotubes make them worthy of being chosen as reinforcement in nanocomposites to extend their operation to a broader range of applications, like conductive nanocomposites, mainly polymer-based matrices. The Nanotubes have chemical affinity and tend to entangle and aggregate. Because of this, to achieve a uniform and remarkable electrical conductivity is hard-to-reach. state of entanglement effects correctly melt methods of polymer blend... 

The consumption of plastics in the world is increasing and this is accompanied by the challenges of production from oil products and carbon footprint, waste production and environmental issues. The solutions to these challenges are material recycling and the production of biocompatible plastics. Polypropylene is a widely used polymer that is commonly used in conjunction with reinforcements such as fiberglass. Natural fibers can be substituted to increase the biocompatibility of the composite, which, despite its many advantages, presents challenges. The most important challenge is the poor adhesion of the fibers and the matrix due to the hydrophilicity of natural fibers and hydrophobicity of...