فهرست مطالب فرهنگ عباسی

This article proposes a paper-based microfluidic chip that can non-invasively measure glucose with optical detection technique using NIR. This paper chip is disposable, portable, low-cost, lightweight, and suitable for point-of-care and cost-effective tests. This paper chip is fabricated with a kind of photoresist that is used in the publishing industry called UV curable resin. This method is chip, simple, and suitable for mass production. This paper chip is used for measuring glucose non-invasively and an interface sensor is designed with an NIR technique that can measure glucose concentration between 60 to 500 mg/dl with voltage range of 630 to 730 mV.

suspension polymerization of styrene in the presence of graphite was carried out. The polymerization reaction kinetics was investigated to gain better insight into manipulating process parameters. The particle size distribution and thermal conductivity of the foams were studied by considering different parameters.

Product characterization and the reaction thermal kinetics were evaluated using differential scanning calorimetry (DSC), thermogravimetry analysis (TGA), particle size distribution and thermal conductivity measurements. The effect of graphite and initiator concentration on the reaction kinetics was investigated.

The results showed that the graphite profoundly reduced the rate of reaction and consequently caused instability in the suspension. By manipulating the process variables such as increasing the amount of stabilizers (1 to 2%) and initiator (up to 0.6% by wt), their frequency and injection time, the polymerization of styrene in the presence of graphite was done. The beads were spherical and the superfine (less than 420 μm) proportion of the product was less than 5%. Through the pre-expansion process, the beads were expanded and the cell structure was uniform. The pentane content of the beads was sufficient (~7% by wt) to successfully sinter the pre-expanded beads in the final molding process. Final foams had 0, 1 and 1.5% graphite. By increasing the graphite content, the thermal conductivity of the foams was decreased. Graphite-containing foams were better thermal insulators than conventional expandable polystyrene. Therefore, for a specific thermal duty, a smaller amount of graphite-containing expandable polystyrene rather than conventional polystyrene is required and consequently, the total cost of the insulation is reduced.

 Recent advances in micro- and nanotechnology have led to possible design of functional micro/nanostructured surfaces with micro/nanotopography features that can exhibit low adhesion properties. An important example of such structures is superhydrophobic surface, which is extremely water repellent. In the present work, the effects of surface microtopography on the wetting of poly(dimethylsiloxane) (PDMS) rubber film with the goal of producing superhydrophobic surface are investigated.

Micropillar arrays inspired by biological structures found in nature are produced on PDMS surface using a soft microlithography technique with different pitch/width ratios. To this end, the masters are fabricated using conventional microfabrication techniques and photolithography. Master designs tested are inverted pillar shape fabricated by anisotropic etching of silicon (reactive-ion etching, DRIE), a high aspect ratio master and a low aspect ratio photoresist master.

Our fabricated pillars have nano-scale ripples that arise from the series of alternating, independent silicon etching and sidewall passivation steps used in the DRIE process. The elastomeric stamps are negative replicas of the masters and they are fabricated by PDMS. The stamps have a regular array of protruding features, in order to make a pattern transfer to the target substrate during m-contact printing. Several pitch/width ratios are configured to optimize the relationship between surface topography and wetting behavior of PDMS film using static water contact angle measurements. We have correlated these structures with PDMS rubber hydrophobicity and have also characterized the transition from the composite (Cassie-Baxter) to wetted (Wenzel) states for different types of surface structures. The surface topography-dependent contact angle of water underwent a transition from Cassie-Baxter to Wenzel states at pitch size ~60 mm.

High friction coefficient of contacting surfaces is one of essential problems in many industries, e.g. automotive, aerospace, home appliances, electronics, etc. It is almost impossible to perform lots of industrial processes without lubricating coatings known as solid film lubricants. On the other hand, some solid film lubricants are toxic and flammable which restricts their use considering health, environment and security. Solid fil lubricants are based on from solid systems used for reducing friction coefficient. Various materials have been used as solid film lubricants with different application methods. Solid film lubricants usually include one or two types of solid particle lubricants dispersed in binder diluted with a solvent to apply on a surface. This article provides are review on solid film lubricants and three main groups of them based on molybdenum sulfide, graphene and polytetrafluoroethylene.

Biodegradable films for food packaging applications have attracted an increasing amount of consideration over the last two decades, predominantly due to environmental pollution and the realization that our petroleum resources are not infinite. Starch, which is one of the natural biopolymers, has been considered as one of the best candidates primarily because of its processbility, availability and price. The main disadvantages of starch films are their pronounced hydrophilic character therefore; they are permeable to water vapor and have usually poor mechanical properties. However, these features can be significantly improved by blending with nanodimension materials such as Montmorillonite (MMT) and Titanium dioxide (TiO2). The main reason for this improvement in comparison with conventional composites is the large surface area which results in high interactions between the nanofillers and polymer when these nano-materials are well dispersed. The behavior of nanocomposite films has been depended to the dispersion of the nanoparticles in the polymer matrix. MMT as a one-dimensional (1D) material is the most commonly used layered silicates. TiO2 as three-dimensional (3D) nanoparticle has been investigated most widely because it is inert, inexpensive and, has a high refractive index with UV shielding potential. The study on films with different dimensions of nanofillers simultaneously is rarely reported. MMT and TiO2 as two inorganic nanofillers have different shapes and structures, so the combination of TiO2 and MMT apparently had a synergistic effect on the starch film properties. The aim of this study was to control particle agglomeration and investigate the synergistic effect of combination of TiO2 nanoparticles and MMT layers and on the surface topography, color, and thermal properties of plasticized starch-MMT-TiO2 nanocomposites.
.First, 100 ml of potato starch solution with a concentration of 4% (w/v) was prepared by dispersion of the starch in distilled water and was gelatinized at 80ºC for 15 min. Different levels of MMT (3 and 5% w/w starch) and TiO2 (0.5, 1 and 2% w/w starch) were dissolved in distilled water and were added to the gelatinized starch after treatment with ultrasound for 30 min. Glycerol, as a plasticizer, with concentrations of 50% (w/w starch) were added to the filmogenic solution. The plasticized starch (PS) based filmogenic solutions were dried in an oven at 45 °C for 15 hours. The surface roughness and topography and thermal properties of the films were determined through atomic force microscopy (AFM) and differential scanning calorimetry (DSC) analysis, respectively. Fourier transforms infrared (FTIR) spectroscopy in the range of 4000 to 400 cm-1. UV-Vis spectroscopy was employed to evaluate the absorbance and opacity behavior of the PS-MMT-TiO2 nanocomposite films in the wavelength range of 200-800 nm. The color parameters of films were measured by a portable colorimeter. Statistical analysis was performed on a completely randomized design with the analysis of variance (ANOVA) and Duncan’s multiple range tests was used to detect differences among the mean values of the films properties
Atomic force microscopy’s images demonstrated an obviously uniform dispersion of MMT and TiO2 nanomaterials in the PS-3%MMT-TiO2matrix with smoother surfaces and a lower roughness parameters than that for the corresponding binary PS-MMT nanocomposites with the MMT filler content (3 wt%). Surface roughness of starch films was changed depending on the MMT and TiO2 content. The results of the roughness parameters and topographic images were confirmed by the high frequency distribution curves. In the PS-3 and 5% MMT films, most parts have height of about 400 and 600 nm, respectively; While the height of the PS-MMT-1% TiO2 bionanocomposites film were 200 and 800 nm. FTIR revealed the hydrogen bonds and electrostatic interactions between nanofillers with starch and themselves by the peaks associated with bond C-O-H at 1142 cm-1 and 990 cm-1 and wide and high intensity IR absorption in the 500-800 cm-1.Evanescence of 3626 and 3452 cm-1 peaks assigned to OH groups of MMT in the PS-3MMT spectrum affirmed the interaction between starch and MMT.Shift in melting temperature and glass transition (Tg) towards higher temperature respectively from 295.1C to 306.3 C and from 199.1 C to 207.6 C were illustrated by DSCresults due to addition of TiO2 in the PS-3%MMT matrix.Improvement of thermal stability might be attributed much jammed and conjugated 3D MMT-TiO2 network combined together, or powerful interaction between PS and nanofillers could also slowdown the polymer chains motion and melting point during heating. These results showed a significant effect of combination of 1D MMT layers and 3D TiO2 nanoparticles on the thermal properties of PS nanobiocomposite starch based films. Montmorillonite did not affect color of nanocomposite. The transparency of a nanobiocomposite film is not significantly varied when the clay layers with about one nm thick are excellent dispersed through the polymer matrix, since such MMT platelets are less than the of visible light wavelength and do not block lights transmission. Transmittance, redness and yellowness of new ternary films decreased when TiO2 was added to PS-3%MMT matrix at 1%. In this case, color difference (ΔE) and whiteness index (WI) are increased 86.6% and 76% respectively.Starch and PS-MMT films were colorless. The presence of TiO2 imparted whiteness to the nanocomposites due to its inherent whiteness. This phenomenon can be enucleated as the large specific surface area and high refractive index of nanosized TiO2 particles were accounted or diffuse reflection of light from the interface of the materials, and consequently, transparency loss of the composite films. UV-Vis spectroscopy was employed to evaluate the absorbance and opacity behavior of the PS-MMT-TiO2 nanocomposite films in the wavelength range of 200-800 nm. Incorporation of TiO2 nanoparticles into the starch film solution caused a significant decrease of transmittance in visible, UV-A (360 nm), UV-B (300 nm), and UVC (240 nm) regions. The results of UV-Vis spectroscopy showed that this type of films could be used as a packaging material to shield against UV and visible light.

Pure mode II fracture toughness of polymethyl methacrylate and its components has been studied by essential work of fracture (EWF) approach via experimental and numerical methods. EWF fracture tests with double edge notched tension (DENT) were performed on the RT-PMMA specimens at room temperature. In this investigation, the mode II fracture of polymethyl methacrylate/graft-acrylonitrile butadiene styrene (PMMA/g-ABS) blends with different weight percentage of rubber (0, 10, 15, and 20) and the thickness of samples 0.8 and 4 millimeters was investigated. The results showed that the value for the specific essential work of fracture given by including lower ligament length may be more accurate, because the ligament is completely yielded. The results also showed that for the load-displacement curves have self-similarity in shapes for the specimens with different rubber content, specimen thicknesses, and ligament lengths and the specific work of fracture (wf) increases significantly with the increasing of rubber content. The non-essential work of fracture (βwp) increases with the increasing of rubber content and the highest value belong to 20% composition in which for both thickness. The highest value of the essential work and the non-essential work of fracture belong to 20% composition in 0.8 mm specimen thickness 98.67 kJ/m2 and 99 kJ/m2, respectively. By changing the thickness of the samples the amount of the essential work of fracture showed significant changes.

In this paper the thermal stability and properties of resole type phenolic resin is investigated. Thermoset phenolic resins have good physical and mechanical properties up to 250 ˚C temperature; however, for high temperature applications modification of thermal stability of resin is very important. Nano silica (SiO2) effect as a filler on thermal stability of the resin is investigated. Thermal properties was studied by means of thermo gravimetric analysis (TGA) to evaluate char yield and differential scanning calorimetric (DSC) to evaluate the resin curing behavior and SiO2 effects on curing reaction heat. Results showed increase of char yield and curing reaction heat in the presence of SiO2. Fourier transform infrared spectroscopy (FTIR) was used to investigate the variation of absorption bands in the presence of SiO2. The results indicated that with an increase of temperature from 200 ˚C to 800 ˚C resin structure was decomposed and volatile compounds including CH4, CO, CO2 and H2O were released out and the resin was carbonized and converted into amorphous carbon. Finally, the microstructure evolution of modified resin and distribution of nano silica in resin matrix were investigated using scanning electron microscopy (SEM). Results showed that silica particles are completely and uniformly distributed in the resin.

This work intends to study the effect of boron carbide (B4C) as filler (1 wt. %) on thermal stability of the resole resin. Thermal properties was studied by means of thermo gravimetric analysis (TGA) to evaluate char yield and differential scanning calorimetric (DSC) to evaluate the resin curing behavior and boron carbide effects on curing reaction heat. Results showed increase of char yield and decrease of curing reaction heating the presence of B4C. The results of Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy coupled with energy dispersive x ray spectroscopy (SEM-EDS) revealed conversion of the B4C to B2O3 which resulted in volume expansion and compensation of the resin shrinkage, which led to the high thermal stability of the compounded resin.

Ultrasound consists of high-frequency sound waves and is widely used in medical purposes and chemical reactions, especially polymerization. The emulsion polymerization of some monomers can occur without the conventional free radical initiators under ultrasonic irradiation. In this paper recent experimental results are reviewed in three sections: (1) nature and source of the free radical for the initiation process; (2) effects of different types of cavitation; and (3) dependence of the polymerization rate and the polymer molecular weight on acoustic intensity, inert gas flow rate, type of surfactant and its concentration, and initial monomer concentration. Since the polymerization of monomer and degradation of polymer occur simultaneously, the ultrasonically initiated emulsion polymerization is complicated. The experimental results show that ionic surfactants play a very important role in obtaining a high polymer yield, and high conversions can be reached in a short time with usage of a high purge rate of N2. An increase in ultrasound intensity leads to an increase in polymerization rate in the range of cavitation threshold and cavitation peak values. Lower monomer concentration favors enhancement of polymerization rate.

Water expandable polystyrene (WEPS) is polystyrene containing water cells as blowing agent. Because of environmental problems of volatile hydrocarbons blowing agents, attempts have been made to replace water as blowing agent. Because of different physical properties of water and volatile hydrocarbons, production condition, physical property and the process of EPS and WEPS will be different. In this paper, the methods of synthesis of WEPS and the recent used methods to improve the final properties of the obtained foam including the synthesis of WEPS in the presence of nanoclay and starch are studied.

The enhanced dispersion of organophilic layered silicates improves the mechanical properties of polymer/ silicate composites. In this work, a hybrid filler system consisting of Cloisite 15A organoclay (OC) and carbon black (CB) was used to improve the properties of the tire tread compounds. The physical and mechanical properties of compounds were assessed by measurement of their cure properties, tensile, crack growth resistance and abrasion tests. The dispersion of organoclay layers was investigated by XRD analysis and transmission electron microscopy. The results have indicated that increases in tensile strength, elongation-at-break and rupture resistance were obtained by replacement of 5 phr CB with OC. However, increases in modulus and abrasion resistance were obtained by replacement of 3 phr CB with OC. Therefore replacement of 3 phr CB with OC was an optimum formulation for tread compound. The results have also indicated that with changing the mixing conditions to enhance the dispersion of clay layers, the mechanical and abrasion properties have improved. The XRD patterns and transmission electron micrographs have revealed that the distances between the layers are increased from 5.5 nm to 13.5 nm.

Environmental and economical advantages of bulk or mass polymerization processes have made this process attractive for ABS producers. When an ABS resin with better optical properties is needed, because of small additive and no use of water and solvent, mass polymerization is the first choice. Processing problems of this method such as lower heat transfer, higher viscosity of reaction mass, and hardness of composition and morphology control in final copolymer make it to play a small role in polymerization of grafted ABS polymers. On the other hand, most of the SAN sales in the world markets are produced by this method. In this study, the bulk processes and different aspects including economical, environmental, and easiness or hardness of process control will be studied. In addition, the effects of polymerization process on the physical- mechanical properties like impact resistance and brightness will be discussed.

It is well known that the toughness of the brittle polymers can be significantly enhanced by incorporation of rubber particles or grafted-rubber particles. One of these materials is acrylonitrile-butadiene-styrene (ABS) which contains dispersed rubber particles with grafted SAN chains on it and styrene-acrylonitrile (SAN) as matrix. Emulsion polymerization (batch or continuous), suspension polymerization (batch), bulk polymerization (continuous), and combined processes and compounding. In this paper, suspension process of ABS production, and the morphology and properties of obtained will be studied.