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    Investigation of Nanoparticles Effects on Rheology of Particulate Filled Polymeric Systems

    , M.Sc. Thesis Sharif University of Technology Mehmandar Oskuei, Erfan (Author) ; Ramazani Saadatabadi, Ahmad (Supervisor) ; Haghgoo, Majid (Co-Supervisor)
    Abstract
    In this study, the effect of molybdenum disulfide nanosheets on the rheological behavior of suspensions was investigated using a polyethylene glycol matrix and glass grain fillers with a particle distribution of 60 to 103 microns. Crude molybdenum disulfide was obtained by single-layer and multilayered molybdenum disulfide nanosheets with thicknesses between 50 and 100 nm using acid, oxidation and heat shock methods. This claim was verified by various tests such as FT-IR, FESEM,EDS, TEM, DLS, XRD and so on. Subsequently, using 10 to 40% volumetric glass beads were prepared from the sample matrix. Stirring and ultrasonic, rheological behavior of these suspensions were investigated using... 

    Role of different compatibilizing approaches on the microstructure and mechanical properties of polypropylene/talc composites

    , Article AIP Conference Proceedings ; Vol. 1593, issue , 15- 19 July , 2014 , pp. 428-431 ; ISSN: 0094243X Homayounfar, S. Z ; Bagheri, R ; Sharif University of Technology
    Abstract
    Since in a highly filled polymer, a major problem arises from non-uniformity of properties due to the poor dispersion of filler, the application of coupling agents have been directed to overcome this problem and also to enhance the mechanical performance of the composites by improving the adhesion at the interface. In this study, a comparison between two major coupling approaches is conducted: 1) Using PPgMA as a kind of compatibilizer which changes the nature of the matrix, 2) Using titanate coupling agent which takes action at the interface and reacts with hydroxyl groups at the inorganic filler surface, resulting in the formation of monomolecular layer on the inorganic surface to increase... 

    A mathematical method for XRD pattern interpretation in clay containing nano composites

    , Article Applied Surface Science ; Volume 318 , 1 November , 2014 , Pages 90-94 ; ISSN: 01694332 Khederlou, K ; Bagheri, R ; Shojaei, A ; Sharif University of Technology
    Abstract
    X-ray diffraction and rheological measurements were used to characterize nanoparticle dispersion in LDPE/LLDPE/nanoclay hybrid nanocomposites. XRD patterns were interpreted with a novel distribution formula and rheological measurements were used to confirm the results. Results of these two methods indicated that increasing clay in all the prepared nanocomposites exhibited a significant improvement in filler-matrix interaction because of increasing the probability of polymer diffusion but further exfoliation need more compatibilizing situations. It seems that this mathematical method could be used for predicting the overall change in clay gallery d-spacing and the extent of... 

    Reinforcing mechanisms of carbon nanotubes and high structure carbon black in natural rubber/styrene-butadiene rubber blend prepared by mechanical mixing-effect of bound rubber

    , Article Polymer International ; Volume 64, Issue 11 , July , 2015 , Pages 1627-1638 ; 09598103 (ISSN) Ahmadi, M ; Shojaei, A ; Sharif University of Technology
    John Wiley and Sons Ltd  2015
    Abstract
    The reinforcing effect of high structure carbon black (HSCB) and multi-walled carbon nanotubes (MWCNTs) on natural rubber/styrene-butadiene rubber blend processed using mechanical mixing was comparatively investigated. In-depth analysis by dynamic mechanical analysis, the Eggers-Schummer model and Medalia's relationship showed that HSCB aggregates provided large internal pores leading to significant immobilized macromolecules in filled rubber. Additionally, a tubular immobilized rubber layer with a thickness of 8nm was estimated for the rubber/MWCNT system based on dynamic mechanical analysis data. The mechanical performance of the HSCB filled blend was higher than that of the MWCNT filled... 

    A new refill friction spot welding process for aluminum/polymer composite hybrid structures

    , Article Composite Structures ; Volume 174 , 2017 , Pages 59-69 ; 02638223 (ISSN) Karami Pabandi, H ; Movahedi, M ; Kokabi, A. H ; Sharif University of Technology
    Abstract
    A new refill friction spot welding process called Threaded Hole Friction Spot Welding (THFSW) was introduced to join AA5052 aluminum to short-carbon-fiber-reinforced polypropylene (PP-SCF) composite sheets. The process was based on filling of the pre-threaded hole by melted and re-solidified polymer. The results showed that THFSW was successful to join aluminum to polymer sheets and the hole was completely filled with melted polymer. Formation of a reaction layer composed mostly of Al, C and O as well as interlocking between the threaded hole and the re-solidified polymer were recognized as main bonding mechanisms. Maximum shear-tensile strength of the joints reached to ∼80 percent of the... 

    Heterogeneities in polymer structural and dynamic properties in graphene and graphene oxide nanocomposites: molecular dynamics simulations

    , Article Macromolecular Theory and Simulations ; Volume 26, Issue 2 , 2017 ; 10221344 (ISSN) Azimi, M ; Mirjavadi, S. S ; Salem Hamouda, A. M ; Makki, H ; Sharif University of Technology
    Wiley-VCH Verlag  2017
    Abstract
    The effect of graphene (G) and graphene oxide (GO), used as the nanofiller in polymer nanocomposites (NC), on the structural and dynamic properties of polymer chains, has been studied by means of molecular dynamics (MD) simulations. Two polymers, i.e., poly(propylene) and poly(vinyl alcohol), are employed as matrices to cover a wider range of polymer–filler interactions. The local structural properties, e.g., density profile, average Rg, and end-to-end distance as well as dynamic properties, e.g., estimated translational and orientational relaxation times, of polymer chains are studied. In addition, the interaction energies are estimated between polymers and nanofillers for different hybrid... 

    Modeling of stiffening and strengthening in nano-layered silicate/epoxy

    , Article International Journal of Engineering, Transactions A: Basics ; Volume 30, Issue 1 , 2017 , Pages 93-100 ; 17281431 (ISSN) Marouf, B. T ; Pearson, R. A ; Bagheri, R ; Sharif University of Technology
    Abstract
    The aim of this paper is to investigate adhesion property between nano-layered filler and the polymer matrix using a combination of experimental and micromechanical models as well as the changes in yield strength and stiffness of a layered silicate-filled epoxy nanocomposite. The results indicate that addition of intercalated layered silicate particles increased Young's modulus and yield strength of the epoxy resin, although the increases in stiffness and yield strength are modest, 30% and 4%, respectively. In addition, experimental results were compared with predictive stiffening and strengthening models. The rule of mixtures provides an upper bound for the modulus in these materials, while... 

    Analytical investigation of composite sandwich beams filled with shape memory polymer corrugated core

    , Article Meccanica ; Volume 54, Issue 10 , 2019 , Pages 1647-1661 ; 00256455 (ISSN) Akbari Azar, S ; Baghani, M ; Zakerzadeh, M. R ; Shahsavari, H ; Sohrabpour, S ; Sharif University of Technology
    Springer Netherlands  2019
    Abstract
    Shape memory polymers (SMPs) are a class of smart materials which can recover their shape even after many shape changes in application of an external stimulus. In this paper, flexural behavior of a composite beam, constructed of a corrugated part filled with SMPs, is studied. This composite beam is applicable in sensor and actuator applications. Since the corrugated profiles display higher stiffness-to-mass ratio in the transverse to the corrugation direction, the beams with a corrugated part along the transverse direction are stiffer than ones with a corrugated part along the length. Employing a developed constitutive model for SMPs and the Euler–Bernoulli beam theory, the behavior of the... 

    Amino-silane-grafted NH2-MIL-53(Al)/polyethersulfone mixed matrix membranes for CO2/CH4 separation

    , Article Dalton Transactions ; Volume 48, Issue 36 , 2019 , Pages 13555-13566 ; 14779226 (ISSN) Ahmadijokani, F ; Ahmadipouya, S ; Molavi, H ; Arjmand, M ; Sharif University of Technology
    Royal Society of Chemistry  2019
    Abstract
    Mixed-matrix membranes (MMMs) are promising candidates for carbon dioxide separation. However, their application is limited due to improper dispersion of fillers within the polymer matrix, poor interaction of fillers with polymer chains, and formation of defects and micro-voids at the interface of both phases, which all result in the decline of the gas separation performance of MMMs. In this work, we present a new method to overcome these challenges. To this end, a series of MMMs based on polyethersulfone (PES) as the continuous polymer matrix and MIL-53-derived MOFs as the dispersed filler were prepared. FTIR-ATR, XRD, TGA, FESEM, and N2 adsorption/desorption analyses were employed to... 

    Thermal synergistic effect in hybrid filler epoxy composites consisting of graphene nanoplatelets and SiC particles

    , Article Thermal Science and Engineering Progress ; Volume 25 , 2021 ; 24519049 (ISSN) Nouri Borujerdi, A ; Kazemi Ranjbar, S ; Sharif University of Technology
    Elsevier Ltd  2021
    Abstract
    The use of hybrid filler is a promising strategy for development of thermally conductive polymer composites. This paper reported the measurement of thermal conductivity of the epoxy composite filled with a hybrid filler of graphene nanoplatelet (GNP) and silicon carbide (SiC) microparticles. For this hybrid filler, the effect of the average size of SiC on composite thermal conductivity was examined. The results showed that the thermal synergistic effect was highly affected by the average size of the SiC. By using a hybrid filler of 11% vol. GNP and 9% vol. 1 µm-size SiC micro-particles thermal conductivity has reached 3.44 W m−1 K−1. This value is 42% higher than the thermal conductivity of... 

    Enhanced microwave absorption performance of BiFeO3 nanopowders coated with Polyindole-PANI co-polymer in ku band frequency

    , Article Journal of Magnetism and Magnetic Materials ; Volume 560 , 2022 ; 03048853 (ISSN) Alamri, S ; Alnujaie, A ; Tan Hoi, H ; Tra Giang, H ; Niaz Akhtar, M ; Sharif University of Technology
    Elsevier B.V  2022
    Abstract
    It's still a significant difficulty to find microwave absorbers that have outstanding microwave dissipation performance in hostile environments. Herein, the core–shell structure of polyindole-PANI co-polymer@BiFeO3 nanocomposite is successfully prepared via in-situ polymerization method. The introduction of a co-polymer shell on the surface of magnetic BiFeO3 nanoparticles considerably tuned the attenuation constant and impedance matching characteristics. The electromagnetic characteristics and microwave absorption feature of the polyindole-PANI co-polymer@BiFeO3 nanocomposites may be found to be influenced by filler loading content regulation. The sample containing 40 wt% of polyindole-PANI... 

    Unified modeling and experimental realization of electrical and thermal percolation in polymer composites

    , Article Applied Physics Reviews ; Volume 9, Issue 4 , 2022 ; 19319401 (ISSN) Sarikhani, N ; Arabshahi, Z. S ; Saberi, A. A ; Moshfegh, A. Z ; Sharif University of Technology
    American Institute of Physics Inc  2022
    Abstract
    Correlations between electrical and thermal conduction in polymer composites are blurred due to the complex contribution of charge and heat carriers at the nanoscale junctions of filler particles. Conflicting reports on the lack or existence of thermal percolation in polymer composites have made it the subject of great controversy for decades. Here, we develop a generalized percolation framework that describes both electrical and thermal conductivity within a remarkably wide range of filler-to-matrix conductivity ratios (Y f / Y m), covering 20 orders of magnitude. Our unified theory provides a genuine classification of electrical conductivity with typical Y f / Y m ≥ 10 10 as... 

    https://www.sciencedirect.com/science/article/abs/pii/S0032386122006103

    , Article Polymer ; Volume 255 , 2022 ; 00323861 (ISSN) Mohammadi, A ; Shojaei, A ; Salkhi Khasraghi, S ; Karimzad Ghavidel, A ; Sharif University of Technology
    Elsevier Ltd  2022
    Abstract
    Present work illustrated that the performance of ultrafine silica (Si) particles was improved considerably by rational hybridization with nanodiamond (ND). For this, Si@ND hybrid particles synthesized by chemical hybridization were incorporated into styrene-butadiene rubber (SBR) up to 10 phr. Scanning electron microscopy revealed coarse flower-like clusters for Si@ND nanohybrids, while Si exhibited rigid agglomerates in SBR. Comparing with physical hybrid (Si&ND) and single Si particles, it was revealed that chemical hybrids synergistically improved tensile properties, like 100% and 135% improvements in tensile strength and elongation at break, respectively. Dynamic mechanical analysis of... 

    Effect of carbon-based nanoparticles on the cure characteristics and network structure of styrene-butadiene rubber vulcanizate

    , Article Polymer International ; Volume 61, Issue 4 , 2012 , Pages 664-672 ; 09598103 (ISSN) Saatchi, M. M ; Shojaei, A ; Sharif University of Technology
    2012
    Abstract
    The network structure of styrene-butadiene rubber (SBR) in the presence of carbon black (CB) with two different structures and multi-walled carbon nanotubes (MWCNTs) was investigated. Swelling behaviour, tensile properties at various strain rates and cure kinetics were characterized. Experimental data were analysed using the Flory-Rehner model as well as the tube model theory. It is found that the network structure of CB-filled SBR follows a three-phase composite model including rigid particles, semi-rigid bound rubber and matrix rubber. This bound rubber is postulated to be critical for the mechanical and deformational properties, development of crosslinking density in matrix rubber and... 

    Evaluation of interfacial layer properties in the polystyrene/silica nanocomposite

    , Article Journal of Applied Polymer Science ; Volume 119, Issue 4 , August , 2011 , Pages 2039-2047 ; 00218995 (ISSN) Mortezaei, M ; Farzi, G ; Kalaee, M. R ; Zabihpoor, M ; Sharif University of Technology
    2011
    Abstract
    Processing conditions and final mechanical properties of polymer nanocomposites are affected by their interfacial layers behavior. However, it is impossible to determine directly the properties of these layers by dynamic rheometry tests. In this work, the interfacial layers properties are evaluated for polystyrene containing silica nanoparticles by the concept of glass-transition temperature shift. The samples were prepared via solution-mixing method and dynamic rheometry was used to determine the viscoelastic behavior of filled polymers in the melt state. This initial step showed that addition of silica particles increased the glass-transition temperature. By preference, decrease in the... 

    Vulcanization kinetics and reversion behavior of natural rubber/styrene-butadiene rubber blend filled with nanodiamond - The role of sulfur curing system

    , Article European Polymer Journal ; Volume 81 , 2016 , Pages 98-113 ; 00143057 (ISSN) Rabiei, S ; Shojaei, A ; Sharif University of Technology
    Elsevier Ltd  2016
    Abstract
    The effect of nanodiamond (ND) particles on the network structure and vulcanization kinetics of natural rubber (NR)/styrene-butadiene rubber (SBR) blend vulcanized by three different curing systems, namely conventional (CV), semi-efficient (SEV) and efficient (EV), was investigated. The filler dispersion, crosslink density, curing kinetics and reversion behavior were fully studied. The state of ND dispersion in the rubber matrix was investigated by the field emission scanning electron microscope (FESEM). Swelling experiments and tensile tests exhibited that upon incorporation of ND crosslink density of NR/SBR blend was enhanced significantly due to the large surface area of nano filler... 

    Behavior of polymer concrete beam/pile confined with CFRP sleeves

    , Article Mechanics of Advanced Materials and Structures ; 2017 , Pages 1-8 ; 15376494 (ISSN) Toufigh, V ; Toufigh, V ; Saadatmanesh, H ; Ahmari, S ; Kabiri, E ; Sharif University of Technology
    Abstract
    This research investigates the flexural behavior of a polymer concrete beam/pile encased with carbon fiber sleeve. The mechanical properties of carbon fiber sleeves in tension and cement and polymer concrete in compression were determined. Polymer concrete beams were tested in flexure to determine the bending moment capacity. Then, the test results were compared to the theoretical model results. Finally, a parametric study was conducted to determine the influence of beam/pile parameters on the capacity of the element. Based on the investigation, carbon fiber sleeve filled with polymer concrete exhibits outstanding structural performance including ductility and bending capacity. © 2017 Taylor... 

    Behavior of polymer concrete beam/pile confined with CFRP sleeves

    , Article Mechanics of Advanced Materials and Structures ; Volume 26, Issue 4 , 2019 , Pages 333-340 ; 15376494 (ISSN) Toufigh, V ; Toufigh, V ; Saadatmanesh, H ; Ahmari, S ; Kabiri, E ; Sharif University of Technology
    Taylor and Francis Inc  2019
    Abstract
    This research investigates the flexural behavior of a polymer concrete beam/pile encased with carbon fiber sleeve. The mechanical properties of carbon fiber sleeves in tension and cement and polymer concrete in compression were determined. Polymer concrete beams were tested in flexure to determine the bending moment capacity. Then, the test results were compared to the theoretical model results. Finally, a parametric study was conducted to determine the influence of beam/pile parameters on the capacity of the element. Based on the investigation, carbon fiber sleeve filled with polymer concrete exhibits outstanding structural performance including ductility and bending capacity  

    In pursuit of a replacement for conventional high-density polyethylene tubes in ground source heat pumps from their composites – a comparative study

    , Article Geothermics ; Volume 87 , September , 2020 Narei, H ; Fatehifar, M ; Ghasempour, R ; Noorollahi, Y ; Sharif University of Technology
    Elsevier Ltd  2020
    Abstract
    Ground-source heat pumps, as the most environmentally friendly and energy-efficient air conditioning technology, suffer from a great required length of ground heat exchanger, partly arising from the low thermal conductivity of high-density polyethylene tubes commonly used in ground heat exchangers. In an attempt to find a replacement with an acceptable thermal conductivity for high-density polyethylene tubes, in this study, first, a comprehensive comparative study on fillers commonly used in thermally conductive polymer composites and resulting high-density polyethylene composites was conducted. Then, based on the advantages and disadvantages presented, an appropriate composite was selected... 

    Mechanical strength of CFRP and GFRP composites filled with APP fire retardant powder exposed to elevated temperature

    , Article Fire Safety Journal ; Volume 115 , 2020 Shekarchi, M ; Majdabadi Farahani, E ; Yekrangnia, M ; Ozbakkaloglu, T ; Sharif University of Technology
    Elsevier Ltd  2020
    Abstract
    Ammonium polyphosphate (APP) is one of the most widely used halogen-free flame retardant, added in various resins to improve the fire properties, such as flame and smoke spread ratings and LOI, of fiber-reinforced polymer (FRP) composites. This paper experimentally investigates the effects of using APP, as a fire-retardant filler, on mechanical properties (i.e. ultimate tensile, flexural, and bond strength) of glass fiber-reinforced polymer (GFRP) and carbon fiber-reinforced polymer (CFRP) composites. Based on two fiber types (i.e. carbon and glass) and three different APP mass fractions in resin (i.e. 0, 20, and 40% of total weight of matrix), six sets of specimens were prepared for each...