Synthesis and Characterization of Cationic Surfactants Based on N‐Hexamethylenetetramine as Active Microfouling Agents

Four cationic surfactants of quaternary hexammonium silane chloride based on hexamethylenetetramine and alkyl chloride were synthesized. The chemical structures of the prepared cationic surfactants were elucidated using Fourier transform infrared (FT‐IR) spectroscopy and mass spectrometry analysis. The surface and thermodynamic properties of the prepared surfactants were also studied. The performance of these cationic surfactants as microfouling agents against two strains of Gram‐negative bacteria, namely, Pseudomonas aeruginosa and Escherichia coli, and two strains of Gram‐positive bacteria, namely, Staphylococcus aureus and Bacillus subtilis, were evaluated as antimicrobial agents. The results showed that the maximum antimicrobial activity was detected for N‐hexamethylenetetramine‐N‐ethyl silane ammonium trichloride (Ah). The maximum and minimum antimicrobial activities were 73 and 60 % against S. aureus and E. coli, respectively, at a concentration of 5 mg/l, pH 7, and 37 °C.     

Influence of Single-Walled Carbon Nanotubes on the Performance of Poly(Azomethine-Ether) Composite Materials

The present work is aimed to fabricate a new set of composite materials containing conducting poly(azomethine-ether) reinforced with single-walled carbon nanotubes in the form of single-walled carbon nanotube/poly(azomethine-ether)_1–5 for excellent enhanced thermal as well as conducting behavior of poly(azomethine-ether). Single-walled carbon nanotubes of variable loading have been embedded into conducting poly(azomethine-ether) using in situ polymerization technique. Before attempting the polymerization, 1,3-thiazole established poly(azomethine-ether) and its conformable monomers have been prepared and their chemical structures have been correlated by spectral analyses. Furthermore, η_inh and M_w values for poly(azomethine-ether) were found 0.89?dL?g^?1 and 39723.6, respectively. The fabricated single-walled carbon nanotube/poly(azomethine-ether)_1–5 composites were specified and characterized by wide-angle X-ray diffraction patterns, Fourier transform infrared spectroscopy, thermal behavior, scanning electron microscopy, and transmission electron microscopy characterization techniques. A perfect indicative response for this composite material was estimated by Fourier transform infrared spectra and X-ray diffraction as well. Both techniques displayed all intensive characteristic peaks regarding single-walled carbon nanotubes and poly(azomethine-ether) in the spectra or diffraction pattern for single-walled carbon nanotube/poly(azomethine-ether)_1–5. The role of single-walled carbon nanotubes on the performance of poly(azomethine-ether) was considerably examined. Single-walled carbon nanotube/poly(azomethine-ether)_1–5 showed relatively higher thermal stability. Single-walled carbon nanotube/poly(azomethine-ether)₁ displayed the lowest final composite degradation temperature value (552°C), whereas single-walled carbon nanotube/poly(azomethine-ether)₅ displayed the highest value (621°C). T₁₀ and T₂₅ values showed a gradual temperature increased while single-walled carbon nanotubes increased. Single-walled carbon nanotube/poly(azomethine-ether)₁ showed the lowest thermal stability and single-walled carbon nanotube/poly(azomethine-ether)₅ showed the highest thermal stability between all fabricated products. Furthermore, transmission electron microscopy images showed a prominent increase in single-walled carbon nanotubes diameters (40–60?nm). The conductivity values were significantly increased while single-walled carbon nanotubes content was increased and reached to the semiconductors. ε′ values were also increased in both single-walled carbon nanotube/poly(azomethine-ether)_4,5 which have higher single-walled carbon nanotubes content.     

Preparation of presintered zirconia blocks for dental restorations through colloidal dispersion and cold isostatic pressing

This work proposes an effective method for dispersion of zirconia suspension for dental block preparation and optimizes the cold isostatic pressing (CIP) pressure to improve the densification of slip-casted zirconia blocks. Two batches of 44 wt% zirconia suspension were prepared using distilled water in a pH 2 medium containing 0.5 wt% polyethyleneimine as dispersant. The first batch was sonicated for different durations (from 5 min to 30 min), and the second batch was dispersed through ball milling at rotational speeds of 200, 300, and 400 rpm for 60, 90, and 120 min. All suspensions were subjected to sedimentation test and particle size measurement. Results revealed that the optimum ultrasonication duration was 10 min, which yielded the smallest particle size of 133 nm. Ball milling at 300 rpm for 120 min achieved the maximum dispersion of particles, with an average size of 75 nm. Under the optimum conditions of ultrasonication duration, ball milling duration, and ball milling speed, the particle size decreased to 48 nm, which is close to the primary particle size. These dispersion techniques and parameters were selected for preparing a suspension to be consolidated into blocks through slip casting and were enhanced through CIP at pressure ranging from 100 MPa to 300 MPa. CIP compaction at 250 MPa significantly increased the shrinkage percentage of green zirconia blocks, with pore radius decreased to 18 nm. The density of zirconia pressed at 250 MPa and presintered at a low temperature of 950 °C was 59% of the theoretical density and was higher than that of commercial presintered blocks. Thus, CIP should be conducted under a compaction pressure of 250 MPa to produce dense and homogeneous zirconia blocks.     

Oligomeric Composition of Polyols From Fatty Acid Methyl Ester: The Effect of Ring‐Opening Reactants of Epoxide Groups

Commercial availability of fatty acid methyl ester (FAME) from palm oil targeted for biodiesel offers a good feedstock for the production of structurally well‐defined polyols for polyurethane applications. The effect of molecular weight (MW), odd and even carbon numbers, and the linear and branched structure reactants used in the ring‐opening reaction of epoxidized fatty acid methyl ester (E‐FAME) on the properties of polyols was investigated. Conversions of E‐FAME to PolyFAME polyols were confirmed by Fourier transform infrared analysis, oxirane oxygen content, and hydroxyl number. Gel permeation chromatography (GPC) calibrated against polyether polyols as a standard and vapor pressure osmometry were used for MW determination. GPC chromatograms of PolyFAME polyols clearly demonstrated the formation of oligomers during ring‐opening reactions. MW, and odd and even carbon numbers in a structure of linear diols and branched diol used in the syntheses of PolyFAME polyols did not have an effect on crystallinity, glass transition, or melt temperatures measured using Differential scanning calorimetry (DSC). PolyFAME polyols ring‐opened with water, methanol, and 1,2‐propanediol contained secondary hydroxyl groups, whereas PolyFAME polyols ring‐opened with linear diols contained a mixture of primary and secondary hydroxyl groups. It was found that the concentration of primary hydroxyl groups increased significantly by increasing the number of carbons from C2 to C3 in the linear diols. The viscosity of PolyFAME polyols also increased with the MW of linear diols used in the E‐FAME ring‐opening reaction. These findings would be beneficial for formulators in choosing the most cost effective polyols for polyurethane formulations.     

Chick Chorioallantoic Membrane (CAM) Assay as an In Vivo Model to Study the Effect of Newly Identified Molecules on Ovarian Cancer Invasion and Metastasis

The majority of ovarian cancer patients present with advanced disease and despite aggressive treatment, prognosis remains poor. Significant improvement in ovarian cancer survival will require the development of more effective molecularly targeted therapeutics. Commonly, mouse models are used for the in vivo assessment of potential new therapeutic targets in ovarian cancer. However, animal models are costly and time consuming. Other models, such as the chick embryo chorioallantoic membrane (CAM) assay, are therefore an attractive alternative. CAM assays have been widely used to study angiogenesis and tumor invasion of colorectal, prostate and brain cancers. However, there have been limited studies that have used CAM assays to assess ovarian cancer invasion and metastasis. We have therefore developed a CAM assay protocol to monitor the metastatic properties of ovarian cancer cells (OVCAR-3, SKOV-3 and OV-90) and to study the effect of potential therapeutic molecules in vivo. The results from the CAM assay are consistent with cancer cell motility and invasion observed in in vitro assays. Our results demonstrate that the CAM assay is a robust and cost effective model to study ovarian cancer cell metastasis. It is therefore a very useful in vivo model for screening of potential novel therapeutics.     

Flow Stress-Strain Rate Behavior of Ti-3Al-2.5V Alloy at Low Temperatures in the Superplastic Range

Flow stress-strain rate behavior of Ti-3Al-2.5V, an α + β titanium alloy was studied at 750 and 800 °C by using the method of crosshead speed cycling. The alloy was found to exhibit superplasticity at these temperatures on the basis of complete flow stress, strain rate and strain rate sensitivity data. Strain-induced softening was observed in the alloy to a small extent at 750 °C and was thought to be related to the grain refinement occurring in both α- and β-phases during the initial stages of deformation. However, at 800 °C the effect was seen only under increasing strain-rate conditions. Flow stress versus strain rate curves generally exhibited only region II which corresponded to low- and intermediate-strain rates and region III corresponding to high-strain rates.     

Vanadia-based coatings of self-repairing functionality for advanced magnesium Elektron ZE41 Mg–Zn–rare earth alloy

A smart vanadia protective coating of self-repairing functionality that has proven to provide superior corrosion resistance for several magnesium and aluminum alloys has successfully been designed by our group. A newly developed series of magnesium alloys, namely ZE41 alloy, has recently been proposed for automotive, electronics and aerospace applications. The advanced ZE41 alloy possesses very low density, high specific strength, and good castability and weldability characteristics compared to aluminum and steel based alloys. However, the corrosion resistance of ZE41 alloy in the presence of corrosive chloride environment is relatively low. The possibility of utilizing such coatings to add self-repairing functionalities to ZE41 alloy was discussed in this paper. The electrochemical corrosion behavior of the vanadia coatings over ZE41 alloy was investigated in 3.5% NaCl solution using EIS, linear polarization and cyclic voltammetry techniques. The optimum conditions for obtaining protective vanadia coatings of self-repairing abilities and improved localized corrosion resistance were determined. Surface examination of the coatings was investigated using SEM-EDS and macroscopic imaging.     

The partial replacement of silica or calcium carbonate by halloysite nanotubes as fillers in ethylene propylene diene monomer composites

The effect of partial replacement of silica or calcium carbonate (CaCO₃) by halloysite nanotubes (HNTs) on the curing behavior, tensile properties, dynamic mechanical properties, and morphological characteristics of ethylene propylene diene monomer (EPDM) composites was studied. Five different compositions of EPDM/Silica/HNT and EPDM/CaCO₃/HNT compounds (i.e. 100/30/0, 100/25/5, 100/15/15, 100/5/25, and 100/0/30 parts per hundred rubber (phr)) were prepared on a two‐roll mill. The results indicated that the replacement of CaCO₃ by HNTs increased the tensile strength, elongation at break (E_b), and tensile modulus of composites from 0 to 30 phr of HNTs whereas for silica, the maximum tensile strength and E_b occurred at 5 phr loading of HNTs with an enhanced stress at 300% elongation (M300). The curing results show that, with replacement of silica or CaCO₃ by HNTs, the cure time (t₉₀) and cure rate (CRI) were decreased and increased, respectively. Scanning electron microscopy investigation confirmed that co‐incorporation of 5 phr of HNTs with silica would improve the dispersion of silica and enhanced the interactions between fillers and EPDM matrix. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

A comparison between experiments and predictions for the blow molding of an industrial part

We present a numerical simulation for the blow molding of an industrial high density polyethylene part. The rheology of the polymeric material is described by means of an integral viscoelastic fluid model with a multi-mode relaxation spectrum. A membrane element is applied for performing the blow molding simulation of geometrically complex objects such as a bottle with a handle; the motion governing equations are described by means of a Lagrangian representation. The contact between the parison and the moving mold is handled by means of a robust algorithm. The numerical tool is applied for the production of a bottle with a handle. The predicted results are compared with their experimental counterparts. In particular, we focus on the thickness distribution of the blow product.     

The inhibition of mild steel corrosion in phosphoric acid solutions by some N-heterocyclic compounds in the salt form

The effect of some quaternary N-heterocyclic compounds on the corrosion of mild steel in solutions of phosphoric acid (H₃PO₄) has been investigated in relation to the concentration of the inhibitor and acid as well as temperature by various monitoring corrosion techniques. Surface morphology was studied by scanning electron microscopy (SEM). Results obtained revealed that these compounds are good mixed-type inhibitors without changing the mechanism of the corrosion process. In general, at constant acid concentration, inhibitor efficiency increased with concentration of the inhibitor. On the other hand, at constant inhibitor concentration, inhibitor efficiency decreased with concentration of the acid up to a critical concentration above which it started to increase. The studied compounds appeared to function through general adsorption following the thermodynamic-kinetic adsorption isotherm. The thermodynamic parameters were determined and discussed. A quantitative correlation between inhibitor structure and inhibition efficiency was discussed.