Sharif Digital Repository

Phase morphology, state of compatibility and various properties of blends of polycarbonate (PC) with bottle-grade and fibre-grade polyethylene terephthalate (BPET and FPET, respectively) were investigated. It was found that these blends have two-phase separated morphology with partial miscibility. Scanning electron micrographs revealed separated domains of PC-rich and PET-rich zones. PC domains appear spherical increasing in size from 2 μm for PC20/FPET80 up to about 5 μm for PC60/FPET40 blend. Further increase in PC content up to 80% caused phase inversion in which FPET appears as finely dispersed domains in continuous PC matrix. Tg of PC-rich phase decreased from 153 deg;C for pure PC down... 

Nylon 6 and 66 were toughened with EPDM-g-MA and SEBS-g-MA and steadystate rheological behaviour of rubbers, nylons and their blends and mechanical properties of nylons and their rubber-toughened blends were investigated. The EPDM maleic grafting preparation was performed In the framework of this study where SEBS-g-MA was obtained from a commercial source. The results showed the ultratoughened SEBS-g-MA blends, whereas EPDM blends under the same blending conditions did not show a significant improvement in toughness. In case of EPDM toughened blends an average of some micrometers was observed for the dispersed EPDM particles. Impact and tensile properties of the toughened blend with 20% of... 

Rubber particle cavitation has been the focus of many investigations because it dramatically affects the mechanical properties of polymeric blends. In this work, the effect of rubber particle cavitation on the mechanical behavior of high-impact polystyrene was studied. The extent of cavitation in rubber particles was varied via different thermal contraction/expansion cycles in the range of -100 to 23°C. Tensile, creep, and Charpy impact tests were conducted to evaluate the effects of the degree of cavitation on the general mechanical properties. The notch-tip damage zone and deformation micromechanisms were also investigated by a transmitted optical microscopy technique to reveal the effects... 

Herein, the fracture toughness of ternary epoxy systems containing nanosilica and hollow glass microspheres (HGMS) is investigated. The experimental measurements reveal synergistic fracture toughness in some hybrid compositions: The incorporation of 10 phr of HGMS and nanosilica alone modify the fracture toughness of epoxy by 39% and 91%, respectively. However, use of 10 phr hybrid modifier can enhance the fracture toughness of the resin up to 120%. Observations reveal different toughening mechanisms for the blends i.e., plastic deformation for silica nanoparticles and crack bifurcation for HGMS. Both of these toughening mechanisms additively contribute to the synergism in ternary epoxies  

Polylactic acid (PLA) and thermoplastic starch (TPS) are known as bio-based and biodegradable thermoplastic polymers that can be used in different applications owing to their inherent physical and mechanical properties. In order to reduce the higher costs of PLA and tuning its physical and mechanical properties suitable for short life packaging applications, blending of PLA with the TPS, more economical biodegradable polymer, has been considered in academic and industrial researches. However, melt blending of PLA with TPS without compatibilization process caused some drawbacks such as coarsening morphology and declining mechanical properties and ductility because of thermodynamic... 

During miscible displacements in fractured porous media, one of the most important factors that plays a significant role in oil production is the matrix-fracture interaction. In this work, a series of hydrocarbon injection experiments have been performed on a fractured glass micromodel that was designed specifically to study matrix-fracture interaction. A high quality image analysis method was used to determine the fluid flow behavior, solvent front movement, and viscous fingering associated with solvent movement in matrix and fractures. Observations showed that in the case of unit viscosity ratio, the injection rate increased the slope of recovery curve and consequently improved the final... 

Binary blends of recycled high-density polyethylene (R-HDPE) with poly(ethylene terephthalate) (R-PET) and recycled polystyrene (R-PS), as well as the ternary blends, i.e. R-HDPE/R-PET/R-PS, with varying amounts of the constituents were prepared by twin screw extruder. The mechanical, rheological, thermal, and scanning electron microscopy (SEM) analyses were utilized to characterize the samples. The results revealed that both R-HDPE/R-PET and R-HDPE/R-PS blends show phase inversion but at different compositions. The R-PET was found to have much higher influence on the properties enhancement of the R-HDPE compared to R-PS, but at the phase inverted situation, a significant loss in the tensile... 

Unsaturated polyester/styrene (UP) resin was filled with nanodiamonds (NDs) containing carboxyl and methacrylate functionalities using mechanical mixing. Field emission SEM exhibited a uniform dispersion of tightly bound aggregates of nanosized spherical NDs with good interfacial interaction. Rheological measurements exhibited a step increment in the shear viscosity of a UP/ND suspension at 0.6 wt% ND resembling a percolation state at this loading. Shear viscosity data supported by dynamic mechanical analysis results suggested the development of effective ND particles in which ND aggregates were covered by only polyester macromolecules. Accordingly, the morphology of UP/ND composites... 

Polymeric materials generally suffer from a low resistance to various types of surface mechanical damage, among which scratch is a prominent example. While several attempts have been made to assess the scratch resistance and its relationship with the bulk mechanical properties in simple polymeric systems, the available research on the polymeric blends is scarce. This study attempts to fill this gap by studying the link between the scratch resistance and mechanical properties in a ternary polymeric nanocomposite, which has proved to feature superior and tunable mechanical properties. For this aim, blends of polypropylene and polyamide 6 were prepared using melt blending with two different... 

With the high rate of mortality associated with breast cancer among women, breast cancer treatment has attracted great deal of attention globally. To reduce the exposure of body organs to high cytotoxicity of the common chemotherapeutic drugs, local co-delivery of selected chemotherapeutics has emerged as a solution. In this work, an electrospun composite including a co-drug-loaded graphene oxide-based nanocarrier is fabricated for local anticancer applications. To increase dispersion and cellular uptake of graphene oxide (GO), first, the hydroxyl groups at the edges of GO are grafted by poly (epichlorohydrin) (PCH) to form GO-PCH. Then, the hydroxyl end groups of PCH are grafted (g) with... 

Alumina flakes were prepared by solution combustion method and milled to provide powder. XRD and SEM data exhibited microsized flakes with 100 nm thickness and nanosized grains. Then the powders were dispersed in polystyrene (PS) and poly methyl methacrylate (PMMA) matrixes and thin sheets of composites were produced by solution method. Mechanical properties of the composites were characterized using tensile test and their fracture surfaces, elemental composition and hydrophobic property were tested by SEM, EDX and contact angle techniques, respectively. The results exhibited better mechanical properties compared to pure polymer samples i.e. the elastic modulus in PMMA and PS composites,... 

Understanding the co-crystallization behavior of ternary polyethylene (PE) blends is a challenging task. Herein, in addition to co-crystallization behavior, the rheological and mechanical properties of melt compounded high density polyethylene (HDPE)/low density polyethylene (LDPE)/Zeigler − Natta linear low density polyethylene (ZN-LLDPE) blends have been studied in detail. The HDPE content of the blends was kept constant at 40 wt% and the LDPE/ZN-LLDPE ratio was varied from 0.5 to 2. Rheological measurements confirmed the melt miscibility of the entire blends. Study of the crystalline structure of the blends using DSC, wide angle X-ray scattering, small angle X-ray scattering and field... 

Novel polyampholytic superabsorbing nanocomposites based on the zwitterionic sulfobetaine monomer [3-(methacrylamido)propyl)]dimethyl(3- sulfopropyl)ammonium hydroxide were synthesized through in situ polymerization in aqueous solution with different contents of an organo-modified clay (OMMT, Cloisite 30B). Structural and thermomechanical properties of hydrogels were characterized by FT-IR, XRD, and DMTA, respectively. Swollen gel strength of hydrogels was determined by a rheological method. Storage modulus of the hydrogels was considerably improved in comparison with its the clay-free counterpart. The nanocomposite hydrogel containing 15% OMMT possessed the highest gel strength. The glass... 

Nanocrystallization kinetics of amorphous Finemet alloy was studied using Vyazovkin advanced isoconversional method under non-isothermal condition. Well known Kissinger model-fitting method and four isoconversional methods of Kissinger-Akahira-Sunose (KSA), Flynn-Wall-Ozawa (FWO), Tang, and Starink were also used for the determination of activation energy. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) patterns were used for thermal and structural analyses, respectively. According to Vyazovkin and other isoconversional methods, the mean value of variable activation energy, as a function of conversion, was obtained as 350 kJ mol-1. While, according to Kissinger method,... 

In this study, the morphological, rheological, and mechanical properties of PP/HDPE blend compatibilized with poly (propylene-g-maleic anhydride) were studied. Necessary blends were prepared using a counter current twin-screw extruder. The blend composition ranged from 10 to 50 wt% of dispersed phase (HDPE) and compatibilizer (MAPP) with two Concentration ranges 10, 20 wt% were used for PP/HDPE (80/20) blend with respect to the dispersed phase (HDPE). The results of morphological studies shows a droplet dispersion morphology in the composition to 50wt% HDPE content, which indicates that HDPE forms a dispersed phase and PP forms a continuous phase in these composition region. Addition of the... 

The catalytic activity of a mixture of ZnCl2: AlCl3 supported on silica gel was evaluated for the alkylation of phenols with benzyl alcohol, tret-butyl alcohol and styrene under microwave irradiation and solvent-free conditions. The catalyst preparation method, its characterization and reusability, were reported. The effect of the phenol to benzyl alcohol ratio and the time of reaction on the phenol conversion and distribution of products was investigated. A conversion percentage up to 97% was achieved when hydroquinone was used. A selective ortho- directed alkylation for phenol, α-naphthol and β-naphthol was observed. © Sharif University of Technology, December 2009  

In this study, fabrication of a three-dimensional porous scaffold was performed using freeze gelation method. Recently, fabrication of scaffolds using polymer blends has become common for many tissue engineering applications due to their unique tunable properties. In this work, we fabricated alginate-gelatin porous hydrogels for wound healing application using a new method based on some modifications to the freeze-gelation method. Alginate and gelatin were mixed in three different ratios and the resulting solutions underwent freeze gelation to obtain 3D porous matrices. We analyzed the samples using different characterization tests. The scanning electron microscopy (SEM) results indicated... 

A novel multi stimuli-responsive silica nanocomposite with a core-shell structure is synthesized using reversible addition-fragmentation chain transfer (RAFT) polymerization. The SiO2 nanoparticles are chemically modified via 3-(trimethoxylsilyl) propyl methacrylate (MPS) which they are used in the core of nanocomposite. The macro-RAFT agent is prepared by RAFT polymerization of N-isopropylacrylamide (NIPAM), spirooxazine acryloyl monomer (SOM), and 2-(dodecylthiocarbonothioylthio)-2-methylpropionic acid (DDMAT as a RAFT agent). Finally, the smart nanocomposite is prepared by reaction between the macro-RAFT agent and 2-(Dimethylamino) ethyl methacrylate (DMAEMA) as a monomer. SOM as a... 

In directional drilling, the most important thing that leads to pulling out the drill string is end of mud motor working life. Considering the working conditions of down hole mud motors; increasing the mechanical properties of their stator’s elastomer is crucial. Some attempts were done to increase the motor performance through geometrical changes but lack of material improvement is significant in previous studies. In this study, NBR/nanoclay composite samples were prepared through melt intercalation in an internal mixer and tested with regard to the temperature and drilling mud of down hole. Hardness, tear, fatigue and tensile test results of neat NBR elastomer and nanocomposite of NBR and...