Sharif Digital Repository

A gas sensor was developed to measure the concentration of binary gas mixtures. This sensor works based on the permeability change of different gas mixtures across the polymeric membranes. Although high values of permeability and selectivity are needed for an ideal separation, the performance of this sensor mainly depends on the permeability factor. Polysulfone and silicone rubber were applied as the membrane base and coat, respectively. Moreover, in contrast to existing polymeric sensors that use hollow fibers, the present sensor is made of flat membranes. This new design is cheaper, smaller, and easier to use in comparison to the hollow fiber polymeric sensors. In order to test the sensor... 

Polycaprolactone (PCL) is a bioresorbable and biocompatible polymer that has been widely used in long-term implants and controlled drug release applications. However, when it comes to tissue engineering, PCL suffers from some shortcomings such as slow degradation rate, poor mechanical properties, and low cell adhesion. The incorporation of calcium phosphate-based ceramics and bioactive glasses into PCL has yielded a class of hybrid biomaterials with remarkably improved mechanical properties, controllable degradation rates, and enhanced bioactivity that are suitable for bone tissue engineering. This review presents a comprehensive study on recent advances in the fabrication and properties of... 

A low cytotoxic metal–organic framework (MOF) UiO-66 (UiO stands for University of Oslo) and NH2-UiO-66, that showed high cell viability of HFF-2 via 3-(4, 5-dimethylthiazol-2-yl) 2, 5-diphenyl tetrazolium assay, was reported as an effective adsorbent (antidotal) agents. The structure of MOFs was confirmed by Fourier transform infrared, Field emission scanning electron microscopy (FESEM) and X-ray diffraction. Thermal behavior of MOFs was investigated using with thermogravimetric analyzer in nitrogen atmosphere to check the thermal stability. FESEM showed NH2-UiO-66 displayed symmetrical crystals with triangular base pyramid morphology, with the particle size around 100 nm and uniform size... 

In the present study the effect of nanodiamond (ND) on the adsorption capacity of Drug has been investigated. Thermal oxidation nanodiamond (OND) was used as adsorbents for Methotrexate adsorption. The surface properties of NDs were studied by Fourier transform infrared spectroscopy and zeta potential. It was determined that thermal oxidation changed the surface properties of ND, including increase the amount of carboxylic acid groups and decreasing the zeta potential of ND by increasing the thermal oxidation time. The adsorption experiments showed that untreated ND (UND) has large adsorption capacity and fast adsorption kinetic for methotrexate (MTX). These results suggest that the... 

A genetic programming technique was employed to develop empirical models for predicting specific wear rate and coefficient of friction on brake friction materials. The models consist of independent variables representing the volume fraction of the ingredients. The average absolute relative error for specific wear rate and coefficient of friction were found to be 1.93% and 1.92%, respectively. The models were also verified by the experimental data used for further control of the formulation. Utilizing Tornado plots, the models were found to be able to properly demonstrate the role of the ingredients on overall tribological performance of the brake friction materials. Moreover, a non-dominated... 

Composites of phenol-formaldehyde (PF) resin with Closite Na+ and Closite 30B up to 20 wt% loadings were prepared by solution mixing. Tensile testing showed that both pristine and organically modified clays increased considerably the mechanical properties of PF resin at 2.5 wt% loading followed by marginal improvement or even sacrificed properties at high loadings. DMA and DSC analyses suggested development of a highly crosslinked and well adhered interphase around silicate layers. A novel three-phase model considering the interphase region was proposed to predict composite modulus. The model was successfully employed to correlate morphological characteristics and mechanical properties of... 

The major obstacles in gas separation by mixed-matrix membranes (MMMs) are poor dispersion and poor affinity between polymers and fillers. The present study demonstrates that these challenges can be overcome appropriately by utilizing a series of synthesized stand-alone MMMs. The matrix used was polymethyl methacrylate (PMMA) and the MMMs were synthesized by in situ polymerization of methyl methacrylate (MMA) in the presence of UiO-66, NH2-UiO-66 and vinyl group attached UiO-66. In situ polymerization of MMA in the presence of vinyl attached UiO-66 resulted in PMMA grafted UiO-66 with a high degree of grafting. Microscopic analysis by field emission scanning electron microscopy (FESEM)... 

The present study demonstrates HEMA-grafted nanodiamond (ND-HEMA)/acrylate-terminated polyurethane-acrylate diluents (APUA) composites as promising materials for bone implant applications. Neat APUA and APUA composites containing ND-HEMA at different loadings up to 2 wt% were prepared by an in situ polymerization method. Morphological analysis demonstrated that ND-HEMAs were actually in the form of tightly bound aggregates which led to formation of big agglomerates at a concentration of 2 wt%. It was also suggested that ND-HEMAs were preferentially localized in the continuous soft domain of APUA; however it interacted by both soft and hard domains. Moreover, ND-HEMAs caused considerable... 

Objective(s): Seizure detection during online recording of electrophysiological parameters is very important in epileptic patients. In the present study, online analysis of field potential recordings was used for detecting spontaneous seizures in epileptic animals. Materials and Methods: Epilepsy was induced in rats by pilocarpine injection. During the chronic period of the pilocarpine model, local field potential (LFP) recording was run for at least 24 hr. At the same time, video monitoring of the animals was done to determine the real time of seizure occurrence. Both power and sample entropy of LFP were used for online analysis. Results: Obtained results showed that changes in LFP power... 

In the present study, thermally oxidized nanodiamond (OND) was first modified non-covalently with dodecylamine (DDA) as corrosion inhibitor. In this respect, reactive primary amine of DDA molecule with high isoelectric point (IEP) could interact easily with negative charge carboxylic acid groups of OND. Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) proved that OND nanoparticle was successfully functionalized by DDA up to approximately 5 wt% grafting contnet. Both OND and dodecylamine modified OND (DND) were loaded in epoxy (EP)/polyamine hardener matrix at the same concentration of 1 wt% and applied on mild steel substrate. Morphology of EP-DND and... 

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 soft template route is reported for the fabrication of polyaniline nanospheres via the oxidative polymerization of aniline in the presence of β-naphthalenesulfonic acid (β-NSA) as both surfactqant and dopant, and ammonium persulfate as oxidant at 2-5°C. Control over the morphology and size of the nanoparticles was achieved by changing the reaction medium via addition of an organic cosolvent (i.e. ethanol or ethylene glycol) and by controlling the concentrations of aniline and β-NSA and the molar ratio of β-NSA to aniline. By this means the size of the β-NSA-aniline micelles and the way that aniline monomer interacts with the micelles were controlled. In fact the lower dielectric constant... 

Surface chemistry of as-received nanodiamond (ND) was first tailored by dry thermal oxidation to obtain carboxylated ND (ND-COOH) and by wet chemistry to obtain ethylenediamine-functionalized ND (ND-EDA). Then, the surface-functionalized ND particles were dispersed in polyamide 6 (PA6) using the melt-mixing method. Transmission optical and scanning electron microscopies indicated a fine dispersion at low nanodiamond concentrations, e.g. 0.25 wt%, particularly with ND-EDA. Differential scanning calorimetry revealed that ND-EDA favoured the α-phase crystal and enhanced the degree of crystallinity of PA6. Experimental data indicated that ND-EDA had considerably improved tensile properties at... 

Metal organic frameworks (MOFs) UiO-66 (UiO stands for University of Oslo) and NH2-UiO-66 were prepared and characterized as sorbent (antidotal agents) for curcumin (CUR) adsorption. The structure of products were characterized by X-ray powder diffraction (XRD), Field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), Attenuated Total Reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), and N2 adsorption–desorption measurements. FESEM showed NH2-UiO-66 displayed symmetrical crystals with triangular base pyramid morphology, with the particle size around 100 nm and uniform size distribution. Adsorption capacities of CUR/MOFs with different mass ratios... 

Biodegradable acrylate-terminated polyurethane/acrylate (APUA) filled with 2-hydroxyethyl methacrylate functionalized carbon nanotube (CNT-HEMA) was prepared by in situ free radical crosslinking. CNT-HEMA enhanced crystallinity of soft domain and caused more phase separation between hard and soft domains of APUA. Tensile testing showed a considerable improvement in elastic modulus (∼160%) and tensile strength (∼30%) at 1 wt% loading. Morphological features of APUA induced by nanotubes were found to be dominant on mechanical properties of APUA/CNT-HEMA. CNT-HEMA increased water contact angle of APUA; however, wettability of APUA/CNT-HEMA maintained in acceptable range for biomedical... 

Biodegradable acrylate-terminated polyurethane/acrylate (APUA) filled with 2-hydroxyethyl methacrylate functionalized carbon nanotube (CNT-HEMA) was prepared by in situ free radical crosslinking. CNT-HEMA enhanced crystallinity of soft domain and caused more phase separation between hard and soft domains of APUA. Tensile testing showed a considerable improvement in elastic modulus (∼160%) and tensile strength (∼30%) at 1 wt% loading. Morphological features of APUA induced by nanotubes were found to be dominant on mechanical properties of APUA/CNT-HEMA. CNT-HEMA increased water contact angle of APUA; however, wettability of APUA/CNT-HEMA maintained in acceptable range for biomedical... 

In this study, the effects of the type and content of reactive diluents on the permeation/separation of carbon dioxide/nitrogen (CO2/N2) through acrylate-terminated polyurethane (APU)-acrylate/acrylic diluent (APUA) composite membranes was investigated. A series of APUs based on poly(ethylene glycol) (PEG)-1000 g mol−1, toluene diisocyanate, and 2-hydroxyethyl methacrylate was synthesized and then diluted with several reactive diluents. The results obtained from differential scanning calorimetry (DSC) and Fourier transform infrared analyses showed that the microphase interference of hard and soft segments increased with increasing reactive diluent content. Furthermore, with increasing alkene... 

The present work focused on the characterization of mechanical properties of novolac phenolic resin (PF) filled with two types of clays, including modified and unmodified ones, and multiwalled carbon nanotube (MWCNT). It was found that the solution mixing method is able to disperse the nanoparticles within the PF resin appropriately. It was also shown that the unmodified clay (Closite Na+) has the highest influence on the mechanical properties possibly due to the good level of dispersion as well as the good interfacial interaction. Theoretical analysis based on the rubber elasticity theory showed that the nanoparticles influence the evolution of crosslinking density and network structure  

Effects of molecular weight and structure of polyamide 6 (PA6) on morphology and properties of PA6/MWCNT prepared by melt mixing were investigated. Microscopic analysis showed fine dispersion of MWCNT within low viscosity PA6s due to domination of melt infiltration into MWCNT agglomerate at low viscosity matrices with linear structure. Rheological data indicated good interfacial interaction with no percolation of MWCNT up to 2 wt% loading. DSC thermograms showed nucleating role of MWCNT on crystallization of PA6s with marginal effect on crystallinity. Experimental data supported with micromechanical model showed limited improvement on mechanical properties, but it was closely consistent with... 

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...