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Papers by navid famili

علوم و تکنولوژی پلیمر, 2008

The preparation and characterization of the vinyltriethoxysilane-modified silica nanoparticles we... more The preparation and characterization of the vinyltriethoxysilane-modified silica nanoparticles were investigated. Also the surface tension of polystyrene, native (hydrophilic) silica and silane-modified (hydrophobic) silica were determined. Two kinds of polystyrene/silica (treated and non-treated) nanocomposites were prepared with different filler loadings by solution method. Their viscoelastic properties were studied by dynamic stress controlled rotary shear rheometer. Solid-like response of polystyrene/native silica nanocomposites were observed in the terminal zone. Solid inclusionsincrease the storage modulus more than the loss modulus, hence decrease the material damping. By increasing filler volume fraction, the particles tend to agglomerate and build clusters. The presence of clusters increases the viscosity, the moduli and the viscoelastic non-linearity of the composites.Treating the filler surface reduces its tendency to agglomerate as well as the adhesion between the partic...

extrusion foaming, nanocomposite, shear rate, nanosilica, polystyrene T his study was an effort t... more extrusion foaming, nanocomposite, shear rate, nanosilica, polystyrene T his study was an effort to control foam structure with controlled shear rate in a slit die with addition of nanosilica in the extrusion process. We used general purpose polystyrene as the matrix, nanosilica as a nucleating agent and nitrogen gas as the blowing agent. For better dispersion of nanoparticles in the matrix, a combination of solution and melt methods were employed. The foams were produced in a twin screw extruder by studying the effects of shear rate on the slit die, size and weight percentage of nanosilica on foam density, cell density and average cell size. Scanning electron microscopicy (SEM) pictures were used to obtain the main characterizing parameters of the foams i.e., cell density and cell size. The results showed that when the shear rate of 8 min-1 on the slit die was increased to 12 min-1 , due to the breakage of the large cells into several smaller cells, there were observed 61% enhanceme...

Polymers for Advanced Technologies, 2011

In this work, the effect of quaternary ammonium salt containing nanoclay content (1–5 wt%) on pha... more In this work, the effect of quaternary ammonium salt containing nanoclay content (1–5 wt%) on phase morphology, rheology, cure kinetics, and mechanical properties of the vinyl ester resin (VER)-based nanocomposites was studied. The morphological characterization including ...

Macromolecular Theory and Simulations, 2012

ABSTRACT The application of the mapping method in finite element modeling is extended to quantita... more ABSTRACT The application of the mapping method in finite element modeling is extended to quantitatively compare mixing in different twin-screw extruder layouts. The mapping method provides volumetric quantities, which are crucial for the analysis and optimization of mixing based on the tracking of particles in the velocity field. A new approach to the mapping method is developed to analyze mixing in complex, dynamic open geometries. Several screw configurations and different types of conveying screws are compared, changing the pitch and gap widths. The volume-weighted intensity of segregation is used as a mixing measure.

Journal of Reinforced Plastics and Composites, 2011

The effects of filler particle size and volume fraction on the immobilized interfacial layer volu... more The effects of filler particle size and volume fraction on the immobilized interfacial layer volume and maximum filler loading of filled polymers are investigated using polystyrene-containing silica nanoparticles. The samples are prepared by solution-mixing method to obtain a better dispersion of silica particles, and dynamic rheometry is used to study viscoelastic behavior of these composites in the melt state. Addition of silica particles increases the glass-transition temperature; this phenomenon is intensified by decreasing the silica particle size. By decrease in size of silica particles, glass transition of filled polymer increases simultaneously with increase of interfacial layer volume fraction, which is related to increase in the total surface area of silica particles. Furthermore, the growth of immobilized interfacial layer volume fraction reduces the maximum filler loading as the filler particle size decreases.

Ceramics International, 2003

Gelcasting is a promising new technology for manufacturing of advanced structural ceramic compone... more Gelcasting is a promising new technology for manufacturing of advanced structural ceramic components. The process involves drying of the “green” gelcast part before densification. Conventional methods in drying green gelcast part, using dry air or gas with a specific condition of humidity and temperature usually are confronted with many difficulties. Non uniform and differential drying in various regions due to

reaction extrusion, co-rotating twin screw extruder, saturation, cross-link, cell density T he co... more reaction extrusion, co-rotating twin screw extruder, saturation, cross-link, cell density T he components' content of foams, based on thermoplastic/thermoset blends, was studied by reaction extrusion method. For this purpose, a co-rotating twin screw extruder was designed and assembled. A high pressure-high temperature vessel was used in which the pressure could be dropped quickly. The foaming was carried out at saturation pressure of 68 bar in 2 s at 170˚C. The results showed that the poly(vinyl chloride)/polyurethane (100/0) sample absorbed up to 8.09 % CO 2 gas and produced foams with a cell average of 6 µm and a cell density of 6×10 9 cell/cm 3. In the blend ratios of 90/10, 80/20, 70/30, 60/40 and 50/50, up to 4% by weight of CO 2 gas was absorbed and no suitable foams were produced. Since the amount of gas diffusivity in the polyurethane was more than that in poly(vinyl chloride), the amount of gas leakage was equally increased by increases in polyurethane content, therefo...

electromagnetic wave absorption, reflection loss, multi-walled carbon nanotubes, polystyrene, nan... more electromagnetic wave absorption, reflection loss, multi-walled carbon nanotubes, polystyrene, nanocomposite E lectromagnetic compatibility (EMC) and electromagnetic interference (EMI) have emerged as key issues with respect to commercial and military purposes in association with electromagnetic waves. The importance of protection against electromagnetic interference in wireless communication and electronic toll collection (ETC) systems has undoubtedly increased over the years. Generally, the electromagnetic absorption properties of material depend on their intrinsic electromagnetic properties such as conductivity, magnetic permeability and dielectric constant and also factors such as thickness and frequency. The effect of each parameter on the absorption performance is yet difficult to comprehend due to the complexity of electromagnetic waves propagation in different media. Addition of pure dielectric or magnetic material to a polymer matrix is a possible way to change electromagnet...

thermoplastic microcellular foam, stabilization, temperature, foam morphology, nucleation M icroc... more thermoplastic microcellular foam, stabilization, temperature, foam morphology, nucleation M icrocellular thermoplastic foams can be usually produced in a one-step batch system using a physical foaming agent which is dissolved in a polymer system under specific pressure and temperature, higher than the critical condition of solvent and the glass transition temperature of polymer and solvent mixture. By application of a sudden pressure drop the foam structure is formed through stages of nucleation, growth and coalescence. After pressure drop, if the foam temperature is reduced below the glass transition of the gas-polymer mixture, the cells stop growing which results in a foam with stabilized morphology. This stabilization stage has not been thoroughly focused in previous studies. In this work, polystyrene as a polymer system and supercritical carbon dioxide as a solvent were used at 18.5 MPa pressure and different temperatures. The stabilization process took place within milliseconds...

The main objective of the present work is to modify the traditional mapping method for the simula... more The main objective of the present work is to modify the traditional mapping method for the simulation of distributive mixing of multiphase flows in geometries involving moving parts such as, internal mixers or twin-screw extruders without a limitation on their geometrical periodicity. The periodicity condition, limits the results of traditional mapping method to tracking mapping mesh between specific discrete time intervals or distances for that geometry is repeated, hence, result is only for fixed orientation of rotors. Imaginary Domain Method is introduced to track mapping mesh from one state to the next free of geometrical periodicity limitations. In this work the method is introduced and its applicability and accuracy is discussed in details. A two-dimensional (2D) simulation of mixing of two Newtonian fluids with different viscosities in an intermeshing internal mixer is used as a test case study. In this example the key issues of ability to predict mixing state in details for all orientations of rotors is presented. To reduce diffusion errors of mapping method in the boundaries of the rotors, mapping mesh refinement technique that relies upon one single reference mesh is also presented.

Composites Science and Technology, 2011

ABSTRACT Filler surface properties and polymer–filler interactions have dominate influence on vis... more ABSTRACT Filler surface properties and polymer–filler interactions have dominate influence on viscoelastic behavior of polymeric matrix composites. When the filler–filler spacing is on the order of the polymeric matrix molecular size, fillers may agglomerate through direct short-range interactions, also by overlapping of interfacial layers of neighboring fillers. In this work the effect of interfacial layer on the viscoelastic properties of silica/polystyrene composite was investigated.The Si/Ps nanocomposites were prepared by solution mixing method, and dynamic rheometry was employed to determine the viscoelastic behavior in the melt state. Experimental results show that, addition of silica nanoparticles to polystyrene matrix would increase the glass-transition temperature of polymer. This increasing will be accelerated by presence of nanoparticles with more filler–polymer adhesion energy, because of more interfacial layer volume fraction. It is helpful in evaluating the volume fraction and equivalent thickness of interfacial layer in polymer nanocomposites. Likewise it is shown that, the dynamic moduli of nanocomposite is enhanced associated with the increase in the glass-transition temperature. This study implies that the main source of increment in both dynamic modulus and glass-transition temperature of polymer nanocomposites is the presence of the immobilized interfacial layer and the secondary filler network.

Key Words polyimide, synthesis, PMI foam, chemical foaming method, physical properties Polymeriza... more Key Words polyimide, synthesis, PMI foam, chemical foaming method, physical properties Polymerization Quarterly, 2013 Volume 2, Number 4 Pages 28-36 P olymethacrylimide (PMI) is known as an excellent heat insulator with high mechanical properties. PMI foam, as a light weight material, combined with its other superior properties, has found applications in aircraft and aeroplane constructions. We have synthesized and developed PMI foam by chemical foaming. The main purpose of this project was to study the effect of processing parameters on the flexibility of PMI with high heat resistance. The processing parameters which were investigated included: the temperature, the method of mixing and the concentration of initiator and foaming agent. Thermal properties were investigated by DSC and TGA tests. Compression strength and DMTA tests were carried out to evaluate the mechanical properties and flexibility of the foam. FTIR was used to explain the chemical structure of the copolymer. abahra...

of immobilized interfacial layer on the maximum filler loading of polystyrene/ silica nanocomposites

Iran. J. Polym. Sci. Technol. (Persian), Vol. 29, No. 1, 73-88 April-May 2016 ISSN: 1016-3255 Onl... more Iran. J. Polym. Sci. Technol. (Persian), Vol. 29, No. 1, 73-88 April-May 2016 ISSN: 1016-3255 Online ISSN: 2008-0883

Applied Rheology, 2016

Linear low density polyethylene (LLDPE)/poly lactic acid (PLA) blends were prepared via different... more Linear low density polyethylene (LLDPE)/poly lactic acid (PLA) blends were prepared via different melt mixing methods. The effects of various blend compositions and two mixing methods on morphological and rheological behavior of the blends were studied. Scanning electron microscope (SEM) was used to investigate morphology behavior of the blends. The rheological studies illustrated that all samples presented shear thinning behavior and the PLA-rich blends exhibited a Newtonian region. It was found from the rheological measurements that the LLDPE/PLA (75/25 w/w) prepared by batch mixer exhibited higher values of storage modulus and complex viscosity, which is in agreement with the morphology results. In addition, using the different mixing methods, significant differences in the morphological results for the LLDPE/PLA (50/50 w/w) blend were observed. Finally, the results showed that the blends prepared by batch mixer exhibited better morphology, higher storage modulus, and complex vis...

Iranian Journal of Polymer Science and Technology Vol. 28, No. 3, 189-195 August-September 2015 I... more Iranian Journal of Polymer Science and Technology Vol. 28, No. 3, 189-195 August-September 2015 ISSN: 1016-3255 Online ISSN: 2008-0883

A major problem in the chemical industries is the separation of waste material produced in the ch... more A major problem in the chemical industries is the separation of waste material produced in the chemical processes. There has been a number of attempts to find a solution to this problem. One of these methods is sedimentation; however, the major drawback of this method is the low velocity of natural sedimentation. By adding particles with larger mass to this system, waste material could be absorbed on their surface and thus increasing the removing rate of the waste material. For this purpose, surface of massive material should be modified for adsorption of the waste material. However, sedimentation velocity is a function of hydrodynamic forces, particle-matrix interaction and particle-particle interaction so that change in surface properties can affect the sedimentation velocity. In this study, a model is developed to predict the effect of particle matrix interaction on sedimentation velocity. A method is also devised to measure sedimentation velocity and to obtain an estimate of par...

Macromolecular Symposia, 2009

Poly(alkyltetrasulfide) is prepared via reaction of ethylene dichloride with sodium tetrasulfide ... more Poly(alkyltetrasulfide) is prepared via reaction of ethylene dichloride with sodium tetrasulfide (Na 2 S 4) in the presence of methyl tributyl ammonium chloride as phase transfer catalyst (PTC). The polysulfide polymer is characterized by CHN analysis, FT-IR, TGA, DTA and DSC techniques.

Journal of Elastomers and Plastics, 2016

Highly filled systems, such as dental materials and tires, have some exceptional properties that ... more Highly filled systems, such as dental materials and tires, have some exceptional properties that make them very special for particular scientists and engineers. In this study, the thermal and dynamic properties of highly nanosilica-filled polystyrene were investigated. Thermal study predicts a phase in the filled system, named as adsorbed polymer, that has a different glass transition temperature ( Tg) compared with the neat polymer. The adsorbed polymer seems to be responsible for special thermal properties of the highly filled system. The dynamic properties of the filled system are observed to have a similar trend as the thermal behavior at different particle sizes and concentrations, both increasing linearly with the increase of volume fraction of adsorbed polymer. However, at higher volume fractions or for smaller particles, this trend changes and the filler networking mechanism is considered to be the reason for this change. Effect of the filler network is studied through the H...

علوم و تکنولوژی پلیمر, 2008

The preparation and characterization of the vinyltriethoxysilane-modified silica nanoparticles we... more The preparation and characterization of the vinyltriethoxysilane-modified silica nanoparticles were investigated. Also the surface tension of polystyrene, native (hydrophilic) silica and silane-modified (hydrophobic) silica were determined. Two kinds of polystyrene/silica (treated and non-treated) nanocomposites were prepared with different filler loadings by solution method. Their viscoelastic properties were studied by dynamic stress controlled rotary shear rheometer. Solid-like response of polystyrene/native silica nanocomposites were observed in the terminal zone. Solid inclusionsincrease the storage modulus more than the loss modulus, hence decrease the material damping. By increasing filler volume fraction, the particles tend to agglomerate and build clusters. The presence of clusters increases the viscosity, the moduli and the viscoelastic non-linearity of the composites.Treating the filler surface reduces its tendency to agglomerate as well as the adhesion between the partic...

extrusion foaming, nanocomposite, shear rate, nanosilica, polystyrene T his study was an effort t... more extrusion foaming, nanocomposite, shear rate, nanosilica, polystyrene T his study was an effort to control foam structure with controlled shear rate in a slit die with addition of nanosilica in the extrusion process. We used general purpose polystyrene as the matrix, nanosilica as a nucleating agent and nitrogen gas as the blowing agent. For better dispersion of nanoparticles in the matrix, a combination of solution and melt methods were employed. The foams were produced in a twin screw extruder by studying the effects of shear rate on the slit die, size and weight percentage of nanosilica on foam density, cell density and average cell size. Scanning electron microscopicy (SEM) pictures were used to obtain the main characterizing parameters of the foams i.e., cell density and cell size. The results showed that when the shear rate of 8 min-1 on the slit die was increased to 12 min-1 , due to the breakage of the large cells into several smaller cells, there were observed 61% enhanceme...

Polymers for Advanced Technologies, 2011

In this work, the effect of quaternary ammonium salt containing nanoclay content (1–5 wt%) on pha... more In this work, the effect of quaternary ammonium salt containing nanoclay content (1–5 wt%) on phase morphology, rheology, cure kinetics, and mechanical properties of the vinyl ester resin (VER)-based nanocomposites was studied. The morphological characterization including ...

Macromolecular Theory and Simulations, 2012

ABSTRACT The application of the mapping method in finite element modeling is extended to quantita... more ABSTRACT The application of the mapping method in finite element modeling is extended to quantitatively compare mixing in different twin-screw extruder layouts. The mapping method provides volumetric quantities, which are crucial for the analysis and optimization of mixing based on the tracking of particles in the velocity field. A new approach to the mapping method is developed to analyze mixing in complex, dynamic open geometries. Several screw configurations and different types of conveying screws are compared, changing the pitch and gap widths. The volume-weighted intensity of segregation is used as a mixing measure.

Journal of Reinforced Plastics and Composites, 2011

The effects of filler particle size and volume fraction on the immobilized interfacial layer volu... more The effects of filler particle size and volume fraction on the immobilized interfacial layer volume and maximum filler loading of filled polymers are investigated using polystyrene-containing silica nanoparticles. The samples are prepared by solution-mixing method to obtain a better dispersion of silica particles, and dynamic rheometry is used to study viscoelastic behavior of these composites in the melt state. Addition of silica particles increases the glass-transition temperature; this phenomenon is intensified by decreasing the silica particle size. By decrease in size of silica particles, glass transition of filled polymer increases simultaneously with increase of interfacial layer volume fraction, which is related to increase in the total surface area of silica particles. Furthermore, the growth of immobilized interfacial layer volume fraction reduces the maximum filler loading as the filler particle size decreases.

Ceramics International, 2003

Gelcasting is a promising new technology for manufacturing of advanced structural ceramic compone... more Gelcasting is a promising new technology for manufacturing of advanced structural ceramic components. The process involves drying of the “green” gelcast part before densification. Conventional methods in drying green gelcast part, using dry air or gas with a specific condition of humidity and temperature usually are confronted with many difficulties. Non uniform and differential drying in various regions due to

reaction extrusion, co-rotating twin screw extruder, saturation, cross-link, cell density T he co... more reaction extrusion, co-rotating twin screw extruder, saturation, cross-link, cell density T he components' content of foams, based on thermoplastic/thermoset blends, was studied by reaction extrusion method. For this purpose, a co-rotating twin screw extruder was designed and assembled. A high pressure-high temperature vessel was used in which the pressure could be dropped quickly. The foaming was carried out at saturation pressure of 68 bar in 2 s at 170˚C. The results showed that the poly(vinyl chloride)/polyurethane (100/0) sample absorbed up to 8.09 % CO 2 gas and produced foams with a cell average of 6 µm and a cell density of 6×10 9 cell/cm 3. In the blend ratios of 90/10, 80/20, 70/30, 60/40 and 50/50, up to 4% by weight of CO 2 gas was absorbed and no suitable foams were produced. Since the amount of gas diffusivity in the polyurethane was more than that in poly(vinyl chloride), the amount of gas leakage was equally increased by increases in polyurethane content, therefo...

electromagnetic wave absorption, reflection loss, multi-walled carbon nanotubes, polystyrene, nan... more electromagnetic wave absorption, reflection loss, multi-walled carbon nanotubes, polystyrene, nanocomposite E lectromagnetic compatibility (EMC) and electromagnetic interference (EMI) have emerged as key issues with respect to commercial and military purposes in association with electromagnetic waves. The importance of protection against electromagnetic interference in wireless communication and electronic toll collection (ETC) systems has undoubtedly increased over the years. Generally, the electromagnetic absorption properties of material depend on their intrinsic electromagnetic properties such as conductivity, magnetic permeability and dielectric constant and also factors such as thickness and frequency. The effect of each parameter on the absorption performance is yet difficult to comprehend due to the complexity of electromagnetic waves propagation in different media. Addition of pure dielectric or magnetic material to a polymer matrix is a possible way to change electromagnet...

thermoplastic microcellular foam, stabilization, temperature, foam morphology, nucleation M icroc... more thermoplastic microcellular foam, stabilization, temperature, foam morphology, nucleation M icrocellular thermoplastic foams can be usually produced in a one-step batch system using a physical foaming agent which is dissolved in a polymer system under specific pressure and temperature, higher than the critical condition of solvent and the glass transition temperature of polymer and solvent mixture. By application of a sudden pressure drop the foam structure is formed through stages of nucleation, growth and coalescence. After pressure drop, if the foam temperature is reduced below the glass transition of the gas-polymer mixture, the cells stop growing which results in a foam with stabilized morphology. This stabilization stage has not been thoroughly focused in previous studies. In this work, polystyrene as a polymer system and supercritical carbon dioxide as a solvent were used at 18.5 MPa pressure and different temperatures. The stabilization process took place within milliseconds...

The main objective of the present work is to modify the traditional mapping method for the simula... more The main objective of the present work is to modify the traditional mapping method for the simulation of distributive mixing of multiphase flows in geometries involving moving parts such as, internal mixers or twin-screw extruders without a limitation on their geometrical periodicity. The periodicity condition, limits the results of traditional mapping method to tracking mapping mesh between specific discrete time intervals or distances for that geometry is repeated, hence, result is only for fixed orientation of rotors. Imaginary Domain Method is introduced to track mapping mesh from one state to the next free of geometrical periodicity limitations. In this work the method is introduced and its applicability and accuracy is discussed in details. A two-dimensional (2D) simulation of mixing of two Newtonian fluids with different viscosities in an intermeshing internal mixer is used as a test case study. In this example the key issues of ability to predict mixing state in details for all orientations of rotors is presented. To reduce diffusion errors of mapping method in the boundaries of the rotors, mapping mesh refinement technique that relies upon one single reference mesh is also presented.

Composites Science and Technology, 2011

ABSTRACT Filler surface properties and polymer–filler interactions have dominate influence on vis... more ABSTRACT Filler surface properties and polymer–filler interactions have dominate influence on viscoelastic behavior of polymeric matrix composites. When the filler–filler spacing is on the order of the polymeric matrix molecular size, fillers may agglomerate through direct short-range interactions, also by overlapping of interfacial layers of neighboring fillers. In this work the effect of interfacial layer on the viscoelastic properties of silica/polystyrene composite was investigated.The Si/Ps nanocomposites were prepared by solution mixing method, and dynamic rheometry was employed to determine the viscoelastic behavior in the melt state. Experimental results show that, addition of silica nanoparticles to polystyrene matrix would increase the glass-transition temperature of polymer. This increasing will be accelerated by presence of nanoparticles with more filler–polymer adhesion energy, because of more interfacial layer volume fraction. It is helpful in evaluating the volume fraction and equivalent thickness of interfacial layer in polymer nanocomposites. Likewise it is shown that, the dynamic moduli of nanocomposite is enhanced associated with the increase in the glass-transition temperature. This study implies that the main source of increment in both dynamic modulus and glass-transition temperature of polymer nanocomposites is the presence of the immobilized interfacial layer and the secondary filler network.

Key Words polyimide, synthesis, PMI foam, chemical foaming method, physical properties Polymeriza... more Key Words polyimide, synthesis, PMI foam, chemical foaming method, physical properties Polymerization Quarterly, 2013 Volume 2, Number 4 Pages 28-36 P olymethacrylimide (PMI) is known as an excellent heat insulator with high mechanical properties. PMI foam, as a light weight material, combined with its other superior properties, has found applications in aircraft and aeroplane constructions. We have synthesized and developed PMI foam by chemical foaming. The main purpose of this project was to study the effect of processing parameters on the flexibility of PMI with high heat resistance. The processing parameters which were investigated included: the temperature, the method of mixing and the concentration of initiator and foaming agent. Thermal properties were investigated by DSC and TGA tests. Compression strength and DMTA tests were carried out to evaluate the mechanical properties and flexibility of the foam. FTIR was used to explain the chemical structure of the copolymer. abahra...

of immobilized interfacial layer on the maximum filler loading of polystyrene/ silica nanocomposites

Iran. J. Polym. Sci. Technol. (Persian), Vol. 29, No. 1, 73-88 April-May 2016 ISSN: 1016-3255 Onl... more Iran. J. Polym. Sci. Technol. (Persian), Vol. 29, No. 1, 73-88 April-May 2016 ISSN: 1016-3255 Online ISSN: 2008-0883

Applied Rheology, 2016

Linear low density polyethylene (LLDPE)/poly lactic acid (PLA) blends were prepared via different... more Linear low density polyethylene (LLDPE)/poly lactic acid (PLA) blends were prepared via different melt mixing methods. The effects of various blend compositions and two mixing methods on morphological and rheological behavior of the blends were studied. Scanning electron microscope (SEM) was used to investigate morphology behavior of the blends. The rheological studies illustrated that all samples presented shear thinning behavior and the PLA-rich blends exhibited a Newtonian region. It was found from the rheological measurements that the LLDPE/PLA (75/25 w/w) prepared by batch mixer exhibited higher values of storage modulus and complex viscosity, which is in agreement with the morphology results. In addition, using the different mixing methods, significant differences in the morphological results for the LLDPE/PLA (50/50 w/w) blend were observed. Finally, the results showed that the blends prepared by batch mixer exhibited better morphology, higher storage modulus, and complex vis...

Iranian Journal of Polymer Science and Technology Vol. 28, No. 3, 189-195 August-September 2015 I... more Iranian Journal of Polymer Science and Technology Vol. 28, No. 3, 189-195 August-September 2015 ISSN: 1016-3255 Online ISSN: 2008-0883

A major problem in the chemical industries is the separation of waste material produced in the ch... more A major problem in the chemical industries is the separation of waste material produced in the chemical processes. There has been a number of attempts to find a solution to this problem. One of these methods is sedimentation; however, the major drawback of this method is the low velocity of natural sedimentation. By adding particles with larger mass to this system, waste material could be absorbed on their surface and thus increasing the removing rate of the waste material. For this purpose, surface of massive material should be modified for adsorption of the waste material. However, sedimentation velocity is a function of hydrodynamic forces, particle-matrix interaction and particle-particle interaction so that change in surface properties can affect the sedimentation velocity. In this study, a model is developed to predict the effect of particle matrix interaction on sedimentation velocity. A method is also devised to measure sedimentation velocity and to obtain an estimate of par...

Macromolecular Symposia, 2009

Poly(alkyltetrasulfide) is prepared via reaction of ethylene dichloride with sodium tetrasulfide ... more Poly(alkyltetrasulfide) is prepared via reaction of ethylene dichloride with sodium tetrasulfide (Na 2 S 4) in the presence of methyl tributyl ammonium chloride as phase transfer catalyst (PTC). The polysulfide polymer is characterized by CHN analysis, FT-IR, TGA, DTA and DSC techniques.

Journal of Elastomers and Plastics, 2016

Highly filled systems, such as dental materials and tires, have some exceptional properties that ... more Highly filled systems, such as dental materials and tires, have some exceptional properties that make them very special for particular scientists and engineers. In this study, the thermal and dynamic properties of highly nanosilica-filled polystyrene were investigated. Thermal study predicts a phase in the filled system, named as adsorbed polymer, that has a different glass transition temperature ( Tg) compared with the neat polymer. The adsorbed polymer seems to be responsible for special thermal properties of the highly filled system. The dynamic properties of the filled system are observed to have a similar trend as the thermal behavior at different particle sizes and concentrations, both increasing linearly with the increase of volume fraction of adsorbed polymer. However, at higher volume fractions or for smaller particles, this trend changes and the filler networking mechanism is considered to be the reason for this change. Effect of the filler network is studied through the H...