Ahmed A. Issa  Mariam Al‐Maadeed  Adriaan S. Luyt  Miroslav Mrlik  Mohammad K. Hassan 《应用聚合物科学杂志》2016,133(26)

The electro‐activity and mechanical properties of PVDF depends mainly on the β‐phase content and degree of crystallinity. In this study, cellulose fibers were used to improve these characteristics. This could be achieved because the hydroxyl groups on cellulose would force the fluorine atoms in PVDF to be in the trans‐conformation, and the cellulose particles could act as nucleation centers. Electrospinning was used to prepare the PVDF/cellulose (nano)fibrous films, and this improved the total crystallinity and the formation of β‐crystals. However, the presence and amount of cellulose in PVDF were found to have little influence on the β‐phase content and on the total crystallinity of PVDF. Improvements in the extent of crystallinity and the β‐phase content were primarily brought about by the chain‐ and crystal orientation as a result of electrospinning. The thermal stability of PVDF in the composites slightly increased with increasing cellulose content in the composites up to 1.0 wt %, while the modulus and tensile strength significantly increased up to the same filler level. The dielectric storage permittivity also increased with increasing cellulose content, but the presence of cellulose had no influence on the dynamics of the γ‐ and β‐relaxations of the PVDF. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43594.  相似文献   

    

Mahmoud Nasr  Mohamed Ateia  Kareem Hassan 《分离科学与技术》2016,51(1):96-105

Treatment of greywater by electrocoagulation using aluminum electrodes was studied. The effects of current-density, electrolysis-time, and inter-electrode-gap on turbidity-removal and electrical-energy consumption were investigated. Under the optimal conditions (J = 12.5 mA/cm², t = 30 min, and l = 0.5 cm), pollutants removal were: COD_total = 52.8%, COD_soluble = 31.4%, BOD_total = 32.8%, BOD_soluble = 27.6%, SS = 64.6%, TN = 30.1%, and TP = 13.6%. The consumed electrical-energy recorded 4.1 kWh/m³ with an operating cost 0.25 US $/m³. Artificial intelligence was developed to simulate the influence of variables on the turbidity-removal. A 3–6–1 neural network achieved R-values: 0.99 (training), 0.84 (validation) and 0.89 (testing). An adaptive neuro-fuzzy inference system indicated that current-density is the most influential input.  相似文献   

    

Mahmoud Kargar  Amir Hossein Behravesh  Hossein Mohammad Taheri 《Polymer Composites》2016,37(6):1674-1680

In this study, mechanical performances of extruded foamed and unfoamed PVC‐wood composites, reinforced with continuous glass fibers, were investigated. A specially designed die was used to incorporate the continuous glass rovings into the extruded rectangular shaped profiles. The experimental variables were the number of continuous glass rovings (0–2‐4) and the presence or absence of the chemical foaming agent. Three point bending tests as well as density measurements were conducted to evaluate the mechanical properties and density reduction upon foaming. The results showed that the flexural strength of the reinforced profiles was significantly increased, as 58% increase in flexural strength was noticed for wood plastic composites (WPCs) reinforced with four glass rovings. The highest density reduction (14%) was observed upon foaming for profiles reinforced with four glass rovings, while resulting in strength deterioration. Moreover, results revealed the remarkable effect of reinforcement on preserving mechanical performance of the foamed samples, as 88% increase in flexural strength of the foamed samples reinforced with four glass rovings was observed compared with the unreinforced foamed ones. For the foamed WPCs reinforced with even two glass rovings, the higher specific strength values were also noticed compared to the unreinforced and unfoamed samples. POLYM. COMPOS., 37:1674–1680, 2016. © 2014 Society of Plastics Engineers  相似文献   

    

Amira Moustafa  Mahmoud M. Abd Rabo Moustafa  Gregory J. Zilinskas  Elizabeth R. Gillies 《加拿大化工杂志》2015,93(12):2098-2106

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Mohamed A. Alnaqbi  Mahmoud A. Mohsin  Reneesh M. Busheer  Yousef Haik 《应用聚合物科学杂志》2015,132(12)

The combination of ionic liquid (IL) associated with microwave energy may have some potential application in the chemical recycling of poly (ethylene terephthalate). In this processes, glycolysis of waste poly (ethylene terephthalate) recovered from bottled water containers were thermally depolymerized with solvent ethylene glycol (EG) in the presence of 1‐butyl‐3‐methyl imidazolium bromide ([bmim]Br) as catalyst (IL) under microwave condition. It was found that the glycolysis products consist of bis (2‐hydroxyethyl) terephthalate (BHET) monomer that separated from the catalyst IL in pure crystalline form. The conversion of PET reach up to 100% and the yield of BHET reached 64% (wt %). The optimum performance was achieved by the use of 1‐butyl‐3‐methyl imidazolium bromide as a catalyst, microwave irradiations temperature (170–175°C) and reaction time 1.75–2 h. The main glycolysis products were analyzed by ¹H NMR, ¹³C NMR, LC‐MS, FTIR, DSC, and TGA. When compared to conventional heating methods, microwave irradiation during glycolysis of PET resulted in short reaction time and more control over the temperature. This has allowed substantial saving in energy and processing cost. In addition, a more efficient, environmental‐friendly, and economically feasible chemical recycling of waste PET was achieved in a significantly reduced reaction time. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41666.  相似文献   

    

Bashar Jazrawi  Nazbanoo Noroozi  Mahmoud Ansari  Savvas G. Hatzikiriakos 《应用聚合物科学杂志》2013,128(6):3592-3600

The melt fracture behavior of several commercial polylactides (PLAs) and poly(ε‐caprolactone) (PCL) is investigated. PLAs and PCL with molecular weights greater than a certain value were found to exhibit melt fracture phenomena in capillary extrusion, which manifests itself as distortions on their surface once the extrusion rate exceeds a critical value. It was found that the addition of a small amount of PCL (typically 0.5 wt %) into the PLA and vice versa is effective in eliminating and delaying the onset of melt fracture to higher shear rates in the capillary extrusion of PLA and PCL, respectively. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013  相似文献   

    

Mahmoud Gorji  Kaveh Mohammadi 《Propellants, Explosives, Pyrotechnics》2013,38(5):715-720

The shelf life of amine based liquid propellant was predicted using Berthelot and Arrhenius approaches and the results were compared. Reduction of the triethylamine concentration to less than 48 wt‐% was taken as the end of shelf life. The γ₁₀ parameter and the activation energy of the Berthelot and Arrhenius approaches were determined to be 1.99 and 64.07 kJ mol⁻¹, respectively. According to the experimental data, the fuel shelf life at 293, 303, and 313 K, was predicted to be 5.7, 2.4, and 1.06 years using Arrhenius; and 3.93, 2, and 1 years using Berthelot approach, respectively. Results showed that the results that Berthelot approach gives lower values for fuel shelf life at ambient temperatures but it gives higher values at higher temperatures. Considering the safety aspect, the lower values are recommended as shelf life of the fuel.  相似文献   

    

Mariam A. Al-Shiekh 《Organic preparations and procedures international》2013,45(3):223-230

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Kyoung-Kyu Choi  Mahmoud M. Reda Taha 《Journal of Adhesion Science and Technology》2013,27(5-6):523-535

We have shown that a significant creep occurs at the concrete–fiber reinforced polymer (FRP) interface based on double shear long-term test. The primary test parameters were the shear stress to ultimate shear strength ratio, the epoxy curing time before loading as well as the epoxy thickness. The test results showed that when the epoxy curing time before loading was earlier than seven days the shear stress level significantly affected the long-term behavior of epoxy at the interfaces, and in particular the combined effect of high shear stress and thick epoxy adhesive can result in interfacial failure if subjected to high-sustained stresses. In this paper, based on the previous experimental observations, an improved rheological model was developed to simulate the long-term behavior of epoxy adhesive at the concrete–FRP interfaces. Furthermore, the newly developed rheological creep model was incorporated in finite element (FE) modeling of a reinforced concrete (RC) beam strengthened with FRP sheets. The use of rheological model in FE setting provides the opportunity to conduct a parametric investigation on the behavior of RC beams strengthened with FRP. It is demonstrated that creep of epoxy at the concrete–FRP interfaces increases the beam deflection. It is also shown that consideration of creep of epoxy is essential if part or the entire load supported by FRP is to be sustained.  相似文献   

    

Mahmoud Ansari  Thanasis Zisis  Savvas G. Hatzikiriakos  Evan Mitsoulis 《Polymer Engineering and Science》2012,52(3):649-662

The capillary flow of a commercial low‐density polyethylene (LDPE) melt was studied both experimentally and numerically. The excess pressure drop due to entry (Bagley correction), the compressibility, the effect of pressure on viscosity, and the possible slip effects on the capillary data analysis have been examined. Using a series of capillary dies having different diameters, D, and length‐to‐diameter L/D ratios, a full rheological characterization has been carried out, and the experimental data have been fitted both with a viscous model (Carreau‐Yasuda) and a viscoelastic one (the Kaye—Bernstein, Kearsley, Zapas/Papanastasiou, Scriven, Macosko, or K‐BKZ/PSM model). Particular emphasis has been given on the pressure‐dependence of viscosity, with a pressure‐dependent coefficient β_p. For the viscous model, the viscosity is a function of both temperature and pressure. For the viscoelastic K‐BKZ model, the time‐temperature shifting concept has been used for the non‐isothermal calculations, while the time–pressure shifting concept has been used to shift the relaxation moduli for the pressure‐dependence effect. It was found that only the viscoelastic simulations were capable of reproducing the experimental data well, while any viscous modeling always underestimates the pressures, especially at the higher apparent shear rates and L/D ratios. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers  相似文献