The effect of electrospinning parameters on the morphology of glass nanofibers

Abstract

Electrospinning of glass nanofibers, as one of the most important techniques for producing nanofibers, was the focus of the present research. This process was done using a carrying polymer in order to modify all important parameters of the process including the solution parameters, the electrospinning voltage, the electrospinning distance and feeding rate of the solution to achieve a desired nanofiber morphology. The produced nanofibers were pyrolyzed at a high temperature to remove the carrying polymer and the FTIR test approved that it was completely removed. The diameter of nanofibers and other details were investigated using SEM images and it was shown that the produced nanofibers have a finer diameter with an average of 228?nm and standard deviation of 46?nm in comparison to other works that reported 500?nm for these characteristics.     

Electrical and rheological properties of PMMA/LDPE blends filled with carbon black

Conductive immiscible multiphase blends of PMMA/LDPE filled with carbon black (CB) were studied in this work. Thermo-electrical behavior of the blends was compared with the composites made up of individual polymers in the blend, PMMA and LDPE filled with CB. The conductivity of the immiscible binary blend at different CB content was followed and modeled using a model circuit in which resistors resembling different phases and the interface between them present in the blend. Electrical percolation threshold was measured for the blend and compared with the single component polymers in order to judge the preferred phase for CB distribution in it. Rheological network formation by CB particles in the blend was also studied using dynamic rheology. The effect of CB loading on the morphology of the multiphase blend was also studied using FESEM images. Theoretical models were also used to predict the percolation thresholds for electrical and rheological network formation and compared with the experimental values.     

Investigation of directly suspended droplet micro extraction method for extraction of trihalomethane and halomethane in water samples

Simple and efficient directly suspended droplet micro extraction (DSDME) in conjunction with gas chromatography-electron capture detector (GC-ECD) has been developed for extraction and determination of Halomethane and Trihalomethane from water samples. In this technique a micro drop of n-hexane is delivered to the surface of an aqueous sample while being agitated by a stirring bar in the bulk of solution. Factors relevant to the extraction efficiency were studied and optimized. The optimized extraction conditions were extraction solvent: n- hexane; NaCl concentration: 1 M; solvent extraction volume: 50 μL; stirring rate: 720 rpm and the extraction time: 5 min. The detection limits of the method were in the range of 0.059–0.137 µg L^?1, relative standard deviation (n = 3) range were 0.019–0.048%. A good linearity (r² ≥ 0.997) and a relatively broad dynamic linear range (10–200 µg L^?1) were obtained and recoveries of method were in the range of 97.69–99.51%. Finally, the proposed method was successfully utilized for pre concentration and determination of halo methane in different real samples. Successfully DSDME technique combined with capillary GC-ECD for the analysis of THMs and HMs in the water investigated samples.     

A multi-product multi-period inventory control problem under inflation and discount: a parameter-tuned particle swarm optimization algorithm

In this paper, a seasonal multi-product multi-period inventory control problem is modeled in which the inventory costs are obtained under inflation and all-unit discount policy. Furthermore, the products are delivered in boxes of known number of items, and in case of shortage, a fraction of demand is considered backorder and a fraction lost sale. Besides, the total storage space and total available budget are limited. The objective is to find the optimal number of boxes of the products in different periods to minimize the total inventory cost (including ordering, holding, shortage, and purchasing costs). Since the integer nonlinear model of the problem is hard to solve using exact methods, a particle swarm optimization (PSO) algorithm is proposed to find a near-optimal solution. Since there is no bench mark available in the literature to justify and validate the results, a genetic algorithm is presented as well. In order to compare the performances of the two algorithms in terms of the fitness function and the required CPU time, they are first tuned using the Taguchi approach, in which a metric called “smaller is better” is used to model the response variable. Then, some numerical examples are provided to demonstrate the application and to validate the results obtained. The results show that, while both algorithms have statistically similar performances, PSO tends to be the better algorithm in almost all problems.     

Synthesis and process modeling of mesoporous γ-Al2O3 granules using the biopolymer chitosan via experimental design

In this study, biopolymer chitosan is presented as a template for synthesizing and shaping the mesoporous γ-Al₂O₃ macrospheres. This porous γ-Al₂O₃ granule has a high surface area (310 m²/g), high pore volume (.6148 cm³/g), and pore diameter between 2 and 10 nm. The full factorial design based on a mathematical model was implemented to study the acid concentration, chitosan amount, ammonia concentration, and aging time affecting the responses (Brunauer–Emmett–Teller surface area and pore volume). Predicted responses were found to be in satisfactory agreement with experimental values (R² = .9580 and .9109, respectively). The adequacy of the model was examined by analyzing the residual distribution plots and Pareto graph. X-ray diffraction, scanning electron microscopy (SEM), thermogravimetric analysis, and N₂ adsorption/desorption techniques are employed to characterize the structure of the prepared γ-alumina sample.     

Exergetic and environmental performance improvement in cement production process by driving force distribution

This paper presents an investigation of the effects of temperature gradient distribution by the aid of a secondary burner on exergetic and environmental functions of the cement production process. For this reason, the burning system of the cement production (kiln &; preheater) process was simulated in four thermal areas. Three lines of cement production with 2,000, 2,300 and 2,600 ton/day were investigated. Fuel injection ratio into the secondary burner, from 10 to 40 percent was studied for each line. The obtained results show that, for cyclone preheaters, fuel injection into the secondary burner up to a proportion resulting in the minimum temperature required for alite formation (2,200 °C) in the kiln burning zone is suitable. For shaft preheaters, however, according to percent calcinations, there exists an optimum proportion for 15 to 20 percent injection fuel into secondary burner. Finally, it was shown that the secondary burner application can reduce the exergy losses about 25 percent, which leads to a reduction of the green house gases of about 35000 cubic meters per year for each ton per day of clinker production.     

Poly1‐hexene: New impact modifier in HIPS technology

Poly1‐hexene was prepared using a conventional heterogeneous Ziegler–Natta catalyst and its stereoregularity was characterized using ¹³C‐NMR analysis. New kind of high impact polystyrene (HIPS) was prepared by radical polymerization of styrene in the presence of different amounts of synthesized poly1‐hexene (PH) as impact modifier (HIPS/PH) and compared with conventional high impact polystyrene with polybutadiene (HIPS/PB) as rubber phase. Scanning electron microscopy (SEM) revealed that the dispersion of poly1‐hexene in polystyrene matrix was more uniform compared with it in HIPS/PB. The impact strength of HIPS/PH was 29–79% and 80–289% higher than that in HIPS/PB and neat polystyrene, respectively. FTIR was used to confirm more durability of HIPS/PH samples toward ozonation. To study the effect of rubber type and amount on the T_gs of polystyrene, differential scanning calorimetry was employed. Results obtained from TGA demonstrated higher thermal stability of HIPS/PH sample in comparison with conventional HIPS/PB one. Our obtained results suggest new high impact polystyrene that in all studied aspects has better performance than the conventional HIPS. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43882.     

Copper Immobilization on Fe3O4@Agar: An Efficient Superparamagnetic Nanocatalyst for Green Ullmann-Type Cross-Coupling Reaction of Primary and Secondary Amines with Aryl Iodide Derivatives

Journal of Inorganic and Organometallic Polymers and Materials - Immobility of copper on magnetic nanoparticles was performed using surface rectification of Fe3O4 with Agar. The magnetic...     

Wrapping carbon nanotubes by biopolymer chains: Role of nanointerfaces in detection of vapors in conductive polymer composite transducers

Chitosan (CS) and hydrophobic‐modified chitosan (HM‐CS) chains were wrapped onto multiwalled carbon nanotubes (MWNTs) and introduced to polyvinyl alcohol (PVA) matrices as nanohybrid conductive polymer composites (CPCs) for detection of polar vapors. The effect of grafted alkyl groups on polarity of CS chains were studied by quantum mechanics (QM). The designed composites were applied as sensitive layers to clarify the response mechanism in CPCs gas sensors. It was realized that the wrapped biopolymers intensely influenced the sensitivity of the composites. Experiment results specified that the nature of biomacromolecules and their interactions with vapor molecules affects the resistance change in CPCs. The higher interaction of CS with polar vapor molecules caused more plasticization of polymer segments in the MWNTs connections. Such phenomenon enhanced the resistance change in the presence of analytes. Moreover, it was inferred that the semiconductor character of MWNTs has an important effect in the final signals. The more polar structure of CS in comparison with HM‐CS enhanced the adsorption of vapor molecules on the surface of MWNTs, and the electron donor analytes decreased the conductivity of p‐type MWNTs increasing the final responses. The presented results corroborate that the performance of CPCs gas sensors could be finely tuned through manipulation of the nanointerfaces. POLYM. COMPOS., 37:2803–2810, 2016. © 2015 Society of Plastics Engineers