Fracture behaviour of polyethylene naphthalate (PEN)

Fracture toughness of a semi-crystalline polyethylene naphthalate (PEN) film of thicknesses 0.050, 0.075 and 0.125 mm was measured as a function of temperature and loading rate using both double edge notched tension (DENT) and single edge notched tension (SENT) specimens. The specific essential work of fracture (EWF) and the multi-specimen J-integral methods were used to evaluate fracture toughness. The variation of the specific total work of fracture (w_f) with ligament length (L) was linear for ligament lengths between 5 and 15 mm. Within this range, w_f versus L was independent of thickness at all temperatures but was dependent on both temperature and loading rate. The specific EWF (w_e) was found to be independent of thickness and loading rate but showed three regions of varying temperature dependence. Between 23 and 80°C (region I) w_e was essentially independent of temperature but increased with temperature between 80 and 120°C (region II) and decreased with temperature thereafter (region III). At glass transition temperature (i.e. 120°C), w_e reached a maximum value of 75 kJ/m². The specific non-EWF (βw_p) increased with both loading rate and temperature. The greatest change in βw_p value with respect to temperature was obtained in region II.The plot of J-integral versus crack extension (Δa) was independent of thickness but was dependent upon temperature. w_e was found to be equivalent to both J_0.2 and J₀.     

Electrical conductivity and percolation threshold of hybrid carbon/polymer composites

The electrical conductivity and percolation threshold of single and hybrid carbon filled composites are experimentally investigated. Polystyrene, carbon fiber (CF) and carbon black (CB) at three CF/CB ratios of 1.67, 3.33, 6.67 were compounded in a twin screw extruder micro‐compounder and compression molded into sheets. The through‐plane and in‐plane electrical conductivity of the composites are measured by 2 and 4 probe techniques. The percolation threshold of the single filler and hybrid composites are determined from the experimental results using a percolation model. The hybrid composites have a higher value of electrical conductivity and lower percolation threshold than the single CF filler composite except for the CF/CB ratio of 6.67. The percolation threshold for the cases of single filler and hybrid composites are modeled. The hard core / soft shell model is used and it is assumed that the percolation in a particle filled system depends on the ratio of tunneling distance to particle diameter. This ratio is determined by modeling single filler composites using the experimental data and kept constant in the modeling of the hybrid system. Finite size scaling is used to determine the percolation threshold for the infinite size hybrid system containing (nanosize) particles and micron size fibers for three CF/CB ratios. The simulation results show that the percolations of hybrid composites have the same trends observed in the experimental results. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41744.     

Resorcinol formaldehyde xerogels modified with mercapto functional groups as mercury adsorbent

Resorcinol formaldehyde xerogels are modified by mercaptopropyl‐trimethoxysilane during the sol–gel process used to produce the xerogel. The chemical modification is confirmed by Fourier‐transform infrared spectroscopy. The xerogel is then used to adsorb mercury ions from aqueous solutions. The effects of the molar ratios of the precursors as well as the catalyst and the modifier are studied on the textural properties of the xerogel and the adsorption efficiency. It is shown that the chemical modification of the resorcinol formaldehyde xerogels creates the chemical sites on the structure of the xerogel to adsorb more mercury ions and increase the adsorption efficiency. At the same time, chemical modification decreases the xerogel surface area which results in a reduction of the mercury adsorption. Therefore, there exists an optimum value for the chemical modification of the xerogel to achieve the highest adsorption efficiency. Adsorption kinetics as well as equilibrium isotherm of xerogels were examined using pseudo‐first‐ and second‐order kinetic equations, and Freundlich and Langmuir isotherm models. The adsorption kinetics was found to follow the pseudo‐second‐order kinetic equations. The experimental data was also fitted into the Longmuir model more precisely comparing the Freundlich model. Finally, a series of mercury adsorption–desorption tests proved that the optimized mercapto‐modified resorcinol formaldehyde xerogel was an efficient reusable adsorbent for mercury ions. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42543.     

Investigation of synergistic effect of nano sized Ag/TiO2 particles on antibacterial,physical and mechanical properties of UV-curable clear coatings by experimental design

The synergistic effect of nano titanium dioxide (10 and 30 nm) and nano silver (10 nm) as antibacterial agents were investigated on UV curable clear coating. Antibacterial and physical–mechanical properties of coating were optimized using experimental design in response surface method. Twenty different samples of nano Ag and nano TiO₂ were prepared in this method. Antibacterial properties on Gram-negative bacteria (Escherichia coli) were investigated. The results revealed that using equal amounts of two sizes of nano TiO₂ promote the antibacterial activity of nano Ag. So, the coating shows strong activity against E. coli. Physical–mechanical properties such as surface hardness, abrasion resistance, scratch resistance and gloss of the coating were evaluated. The results depicted appropriate physical–mechanical properties. Also, scanning electron microscope (SEM), atomic force microscope (AFM) and Fourier transform infrared (FT-IR) spectroscopy were used to study the effect of nano particles on coating properties.     

Enhanced oil recovery from carbonate reservoirs by spontaneous imbibition of low salinity water

An experimental study was performed to investigate the impact of low salinity water on wettability alteration in carbonate core samples from southern Iranian reservoirs by spontaneous imbibition. In this paper, the effect of temperature, salinity, permeability and connate water were investigated by comparing the produced hydrocarbon curves. Contact angle measurements were taken to confirm the alteration of surface wettability of porous media. Oil recovery was enhanced by increasing the dilution ratio of sea water, and there existed an optimum dilution ratio at which the highest oil recovery was achieved. In addition, temperature had a very significant impact on oil recovery from carbonate rocks. Furthermore, oil recovery from a spontaneous imbibition process was directly proportional to the permeability of the core samples. The presence of connate water saturation inside the porous media facilitated oil production significantly. Also, the oil recovery from porous media was highly dependent on ion repulsion/attraction activity of the rock surface which directly impacts on the wettability conditions. Finally, the highest ion attraction percentage was measured for sodium while there was no significant change in pH for all experiments.     

Multi-Objective Optimization Model for the Allocation of Water Resources in Arid Regions Based on the Maximization of Socioeconomic Efficiency

The escalating world population has led to a drastic increase in water demand in the municipal and drinking water, agriculture and industry sectors. This situation necessitates application of effective measures for the optimal and efficient management of water resources. With this respect, a two-objective socioeconomic model (aimed at job creation) has been presented in this study for the optimum allocation of water resources to industry, agriculture and municipal water sectors. In the agriculture sector, the production function of each product has been determined and then, based on the production functions, areas under cultivation, product yield and the income obtained from each product, the combined objective function has been specified. In the industry sector, since water demand is a function of the amount of produced products, price of supplied water and the price of other supplies, the demand function of this sector was determined regionally. Also, considering the existing necessity in meeting the municipal water requirement, the total amount of water needed by this sector was fully allocated. Then by using two meta-heuristic algorithms, i.e. genetic algorithm (GA) and particle swarm optimization (PSO), the objective functions were maximized and the water resources were optimally allocated between agriculture and industry sectors and the results were compared. Ultimately, comparing the results gained by PSO and GA algorithms, PSO with an economic and profit growth of 54 % and a 13 % rise in employment relative to the base condition, turned out to be more efficient in this application.     

A hybrid model of fuzzy goal programming and grey numbers in continuous project time,cost, and quality tradeoff

The purpose of this paper is to develop current mathematical models of cost, time, and quality tradeoffs in conditions that parameters of project activities are estimated uncertainly by grey numbers. In some projects like construction projects, activities can be done within a much shorter time by increasing in the resources, while project's cost may rise at the same time. In such situations, managers are usually required to determine the best combination of cost, time, and quality parameters of the activities, although their information regarding these parameters is limited and rather incomplete. The greyness of these parameters in the proposed method can aid managers to deal with these conditions. The most important aspect of the proposed model is that it considers uncertainty of the project planning data in the form of grey numbers. A combination of fuzzy goal programming and grey linear programming is also developed to solve the proposed model. Finally, this model will provide the managers with a stronger ability to face with uncertainty in project management and planning. The application of this model is examined in a numerical example. As its major finding, the model determines an optimal range in which the project managers can respond to intrinsic changes that may occur in the parameters during a project.     

Correction factors for safe performance of API X65 pipeline steel

Prediction of required Charpy energy for fracture arrest is vital for safe performance of gas transportation pipelines. This is commonly estimated through failure models calibrated in the past on fracture data from combined Charpy tests and full-thickness burst experiments. Unfortunately, such pipeline failure models are unable to correctly predict the minimum arrest toughness of thermo-mechanical controlled rolled (TMCR) steels. To refine the existing failure models, different empirical adjustments have been proposed in recent years. In this paper, similar correction factors were derived from fracture information of instrumented Charpy impact tests on API X65 steel. The contribution of different fracture mechanisms of impact test specimens was determined through energy partitioning analysis. Parts of the energy contribution were correlated then to the source of uncertainty observed in similar experiments. The applied technique was similar to that of previous studies on X70 and X100 steels, and proved to be encouraging in giving consistent results compared to available test data.     

Ranking function-based solutions of fully fuzzified minimal cost flow problem

The aim of minimal cost flow problem (MCFP) is to find the least transportation cost of a single commodity through a capacitated network. This paper presents a model to deal with one particular group of such problems in which the supply and demand of nodes and the capacity and cost of edges are represented as fuzzy numbers. For easier reference, hereafter, we refer to this group of problems as fully fuzzified MCFP. To represent our model, Hukuhara’s difference and approximated multiplication are used. Thereafter, we sort fuzzy numbers by an order using a ranking function and show that it is a total order, i.e., a reflexive, anti-symmetric, transitive and complete binary relation. Utilizing the proposed ranking function, we transform the fully fuzzified MCFP into three crisp problems solvable in polynomial time. From this standpoint, combinatorial algorithms are provided to solve the above-mentioned problem and find the fuzzy optimal flow. Furthermore, the proposed order is related to the importance weights of the center, the left spread and the right spread of each fuzzy number. Thus, this method is capable of handling the decision maker’s risk taking. By comparing some previous ranking function-based works with our method, the efficiency of the latter is revealed. Finally, an application of our proposed method to petroleum industry is presented.