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51.
Manal Shaker 《先进技术聚合物》1997,8(6):327-334
Ultra high molecular weight polyethylene (UHMW-PE) fibers were used in a chopped form and at different concentrations as a reinforcing material in ethylene–propylene–diene terpolymers (EPDM). The effect of radiation dose and fiber concentration on the mechanical properties of the vulcanized rubber composites obtained was measured. It was found that γ-irradiation improves the interfacial adhesion between UHMW-PE fiber (Spectra 1000) and EPDM matrix which was detected by scanning electron microscopy (SEM). In addition, the Young modulus of the composites increases as the irradiation dose increases. Increasing the concentration of the fibers up to 40 phr leads to an enhancement in mechanical properties and swelling resistance of obtained composites, especially in the absence of carbon black. The absolute value of the modulus increased by a factor of at least two with the addition of carbon black. Moreover the tear strength of reinforced and filled EPDM was improved with respect to reinforced rubber. © 1997 John Wiley & Sons, Ltd. 相似文献
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53.
Hassan Mallaekeh Alireza Shams Mohammad Shaker Ehsan Bahramzadeh Donya Arefi 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2014,88(12):2081-2086
In this paper the complexation reaction of the 5,5′-(2E,2′E)-2,2′-(ethane-1,2-diylidene)bis(hydrazine-1-yl-2-ylidene)bis(4-amino-4H-1,2,4-triazole-3-thiol) ligand (HYT) with Cd2+ education was studied in some binary mixtures of methanol (MeOH), n-propanol (PrOH) and dimethyl-formamide (DMF) at different temperatures using the conductometry and spectrophotometry. The stability constants of the complex was determined using a GENPLOT computer program. The conductance data and absorbance-mole ratio plots show that in all solvent systems, the stoichiometry of the complex formed between (HYT) and Cd2+ cation is 1: 1. The obtained results show that the stability of (HYT)-Cd complex is sensitive to the mixed solvents composition. The values of thermodynamic parameters (ΔG °, ΔH °, and ΔS °) for formation of (HYT)-Cd complex were obtained from temperature dependence of the stability constant using the van’t Hoff plots. The results show that in most cases, the complex are enthalpy destabilized but entropy stabilized and the complex formation is affected by pH, time, temperature and the nature of the solvent. 相似文献
54.
Asmaa H. Mohamed Hager S. Abdelmeged Raafat M. Shaker Fathy F. Abdel-Latif 《Journal of heterocyclic chemistry》2021,58(12):2372-2380
The present article describes a facile one-pot synthesis of a new series of 4,4′-(1,4-phenylene)-dipyrimidines ( 6a–c and 10a, b ) by the reaction of terephthalaldehyde ( 1 ), 2-acetylthiophene, and/or nitriles with S-benzylthiouronium chloride 3a . And also, the di-pyrimidinones 13a-d were obtained by the reaction of different amidines 3a–d and ethyl cyanoacetate ( 11 ) with terephthalaldehyde ( 1 ) under solvent-free conditions in the existence of sodium hydroxide which is found to be a more efficient base for these reactions. The final products were characterized by spectral data and elemental analysis, IR, MS, 1 H, and 13 C NMR spectroscopy. 相似文献
55.
M. S. Masoud T. S. Kassem M. A. Shaker A. E. Ali 《Journal of Thermal Analysis and Calorimetry》2006,84(3):549-555
Iron, cobalt, nickel,
copper, zinc, cadmium and mercury murexide complexes have been prepared and
characterized. The thermal properties of these complexes are studied deeply
by DTA technique where their thermal peaks are explained. The multi-stages
thermal decomposition mechanism is proposed. The thermodynamic parameters
of the decomposition steps are calculated. The entropy change values for all
complexes are of the same magnitude and all transition states of the thermal
reactions are more ordered than the reactants. The thermal reactions proceed
in complicated mechanisms. The fractions appeared in the calculated orders
of the thermal reactions confirmed that these reactions proceeded via complex
mechanisms. 相似文献
56.
Saker Saloum Samer Abou Shaker M.Nidal Alkafri Asmhan Obaid Rokayya Hussin 《Surface and interface analysis : SIA》2019,51(7):754-762
Plasma-polymerized hexamethyldisiloxane (pp-HMDSO) thin films have been deposited in a radiofrequency (RF) remote plasma-enhanced chemical vapor deposition (PECVD) system, on different types of substrates: silicon wafers, glass, quartz crystals, and chemiresistor structure. The as-grown thin films have been post treated in two types of reactive plasmas produced in SF6 and O2 gases. The effect of this surface modification on different properties of the as-grown pp-HMDSO thin film (chemical structure, elemental composition, surface morphology, film density and thickness, optical bandgap, and electrical resistivity) has been investigated. It is found that SF6 plasma and O2 plasma surface modifications of the as-grown pp-HMDSO thin film induce property changes different from each other. SF6 plasma converted the as-grown pp-HMDSO film to a more porous material and caused a narrowing of its optical band gap of about 33%, while O2 plasma induced a lowering of film electrical resistivity of about two orders of magnitude. 相似文献
57.
58.
An innovative approach to the design of the gear-tooth root-profile, and its effects on the service life is reported in this paper. In comparison with the widely used trochoidal and the recently proposed circular-filleted root profiles, the optimum profile proposed here is a \(G^2\)-continuous curve that blends smoothly with both the involute of the tooth profile and the dedendum circle. Following the AGMA and ISO standards for fatigue loading, the von Mises stress at the critical section and stress distribution along the gear tooth root are studied. The process leading to gear-tooth failure is composed of the crack initiation phase, in number of cycles \(N_i\), and the crack propagation phase, in \(N_p\) cycles. The strain-life (\(\epsilon\)-N) method is employed to determine \(N_i\), where the crack is assumed to initiate at the critical section. Based on the ANSYS crack-analysis module, the effects of \(G^2\)-continuous blending on the stress intensity factor (SIF) are investigated for different crack sizes. Paris’ law, within the framework of Linear Elastic Fracture Mechanics, is used to correlate the SIF with crack size and, further, to determine \(N_p\). The optimum profile provides a significant reduction in SIF and improvement in both \(N_i\) and \(N_p\). Spur gears are made of high-strength steel alloy 42CrMo4, the effects of its properties and surface treatment on service life improvement not being included in this study. 相似文献
59.
Salt effects on the reactivity of base hydrolysis of Fe(II) chelates [naphthylideneisoleucinate (nili), naphthylideneleucinate (nli), naphthylideneserinate (nsi), salicylideneisoleucinate (sili), salicylideneleucinate (sli), salicylidenemethioninate (smi), and salicylidenetryptophanate (sti)] have been investigated in aqueous media containing alkali metal halides and tetra‐n‐butylammonium bromide (TBAB). NaCl and NaBr exhibited different reactivity trends from those of KBr and TBAB. The observed patterns vary markedly with complex hydrophobicity. Generally, the presence of the salt markedly enhances the rate compared to its absence. This behavior agrees with the anionic nature of the transient species. With increasing added NaCl and NaBr, the rate of the reaction decreases. The rate decreases and then increases on increasing the concentration of KBr and TBAB. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 592–601, 2003 相似文献
60.