Sharif Digital Repository

A series of poly(ethylene-co-vinyl acetate) (EVA)-based hot melt adhesives containing either a raw rosin or a hydrogenated rosin ester have been prepared to investigate variation of viscosity, softening point and peel adhesion with composition. Adhesion of the prepared hot melt adhesive to the substrate was characterized by T-peel strength test. Increasing rosin had a prominent effect on the adhesion. Viscosity decreased and softening point increased as the wax content increased. Addition of zinc borate as a flame retardant decreased T-peel energy and increased the viscosity and softening point of the samples. Higher peeling strength accompanied with a good softening point and viscosity... 

Many efforts have been performed on the poly(vinylidene fluoride), PVDF, due to its piezoelectric, pyroelectric and ferroelectric potentials. In this thesis Poly (vinyldene Flouride) (PVDF)/Poly (vinyl Asetate) (PVAc)/Multi-walled carbon nanotubes (MWCNT) and Poly (vinyldene Flouride) (PVDF)/Poly (vinyl Asetate) (PVAc)/Graphene Oxide nonasheets (GOn) nanocomposite films were prepared via solution casting method. The effect of concentration of PVAc, MWCNT and graphene oxide on PVDF nanocomposites were investigated. Graphene oxides synthesized by modified Hummer’s method. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) results showed that the crystalline structure of... 

Power amplifiers are used as the last block of transmitters. This block can be categorized as the one of most important part in communication systems. However, in transmitter systems which require high power to create stable link with the receivers, fabrication process like CMOS are unable to provide such level of power. Thus, designers employ another group of integrated circuits which names MMIC that offers this capability to designers.
MMIC is the abbreviation of Microwave Integrated Circuit which is implemented in compound substrates like GaAs. Monolithic microwave integrated circuits enable the implementation of amplifiers in small size, large number, with high precision and... 

In this work, magnetite (Fe3O4) nanoparticles with an average siz21.9nm
modified by oleic acid were prepared by the coprecipitation method, which can linked well with organic molecules because of the presence of C-O-C on their surface. Then magnetic poly(lactic acid) (PLA)/ poly(ethylene glycol) (PEG) microspheres were prepared by the single emulsion solvent evaporation technology. The incorporation of magnetit nanoparticles and dox into the PLA matrix was confirmed by FTIR. XRD and VSM confirmed the existence of MNPs in the microspheres which maintained superparamagnetic behavior with a saturation magnetization of 50.69 emu/g.Electron microscopy SEM showed that the magnetic microspheres... 

Polyvinylidene fluoride (PVDF) is remarkable since its mechanical properties, chemical stability and significant ferroelectricity. This Polymer has a simple chemical structure and can be found in five different crystal phases (α,β ,ɣ,δ and ε). Between these phases, beta shows a substantial pyro and piezoelectric activity since its great dipole moment. In this study PVDF/Poly(vinyl acetate)/Nanodiamond (ND) nanocomposite films were synthetized by solving in dimethylformamide adding ND particles to PVDF/PVAc blend in order to improve mechanical and piezoelectric properties. Scanning electron microscopy results showed that PVDF/PVAc are miscible and lead to a single crystal phase and dispersion... 

The purpose of this project was to produce and examine the Poly(lactic acid)/poly(ethylene-co-vinyl acetate)/ nano-clay nanocomposite by solution casting that can be used for food packaging. In this study, it was observed that solvent evaporation at 4°C gives uniform films, without phase separation and free of voids, in a certain composition of polymers related to the rate of solvent evaporation.According to DMTA results Poly(lactic acid) and poly(ethylene-co-vinyl acetate) with 28% vinyl acetate, were compatible in less than 10% poly(ethylene-co-vinyl acetate) content in blend of them. Also, results of SEM tests showed that ethylene-co-vinyl acetate particle size in blends with 3 and 5... 

Polyvinylidene fluoride is highly regarded by researchers due to its piezoelectric properties, mechanical properties, chemical and thermal stability and biocompatibility. This thermoplastic polymer has a semi-crystalline structure and, depending on the crystallization conditions, has five distinct crystalline phases α, β, γ, δ and ε. The β, γ and δ phases are electroactive, and among them, the β phase has high piezoelectric activity due to its high dipole moment. This study focuses on increasing the amount of β phase in polyvinylidene fluoride and increasing its piezoelectric property. Polyvinylidene fluoride is highly miscible with oxygen containing polymers such as polymethyl... 

In this research, the EVA/BT/MWCNT nanocomposites were prepared via the solution casting method in the various weight fractions of Barium titanate (BT) and multi-walled carbon nanotubes (MWCNT). Barium titanate-based ceramic material has a high dielectric constant, and it is used in the manufacture of sensors, capacitors, and electrical memories. On the other hand, multi-walled carbon nanotubes, due to electric charges on their surface and high electrical conductivity, can affect the dielectric properties combined with barium titanate and the hybrid of these two materials a polymer matrix suitable for special applications. In this study, ethylene-vinyl acetate (EVA) copolymer was used as a... 

Successful treatment of bone infections is a major orthopedic challenge due to the physiological and anatomical features of bone. In this project, we prepared a drug delivery system with injectable and biodegradable polysaccharide agar containing alginate, polyvinyl alcohol and hydroxyapatite nanocarriers composite microspheres. Alginate and polyvinyl alcohol composite microspheres are crosslinked by calcium and freeze-thawing technique. Using the freeze thawing process for polyvinyl alcohol crosslinking, in addition to alginate crosslinking, improved hydrogel swelling behavior and enhanced drug loading and thus slowed drug release, drug loading increased with increasing PVA percentage from ... 

In recent years, the tendency to use biodegradable and biocompatible polymer nanoparticles for drug delivery applications has been increasing, the reason for this being the possibility of precise control of the drug release rate, ease of use, and no need for external Surgery after the release of the drug, increases the therapeutic efficiency of the drug and reduces the side effects with its precise transfer. In this research work, drug carrier nanocomposites were prepared from polylactic acid (PLA), polyethylene glycol (PEG) and hydroxyapatite (HAp) and for the controlled release of ciprofloxacin (CIP). It was used to treat bone infections. The drug loading efficiency for nano-carriers was... 

Composite film PLA/PVDF and nanocomposite films PLA/PVDF/MWCNT with a solution method by solvent Dimethyl formamide was prepared at 65◦c. poly vinylidene fluoride as matrix phase and poly lacticacid was used an amplifier. In the next sextion multiwalled carbon nanotubes were added to the PLA/PVDF composite.Scaning Electron microscope results, showed that the PLA/PVDF composite and PLA/PVDF/MWCNT nanocomposites, non porous structure and carbon nanotubes in the polymer matrix have been well dispersed. The impact of nanoparticles in the polymer matrix by X-Ray Diffraction and Differential Scaning Calorimetry was investigated. With differential scaning calorimeter (DSC) and stress strain test,...