Properties of silane grafted polypropylene/montmorillonite nanocomposites

Polypropylene/montmorillonite nanocomposites were prepared by melt compounding using organosilane modified polypropylene (PP-g-VTES) as compatibilizing agent. The materials were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), tensile modulus, and Izod impact strength. Addition of PP-g-VTES improved clay dispersion, as shown by the distribution of platelets per particle, and improve the interaction between clay and polymer matrix. Crystallization peak temperature (T_p) was increased in 10 °C using PP-g-VTES as compatibilizing agent. However the crystallization process and its rate were unmodified. The tensile modulus of compatibilized nanocomposite is 1.5 times higher compared to pure PP.     

Mass and heat transfer study in solids of revolution via numerical simulations using finite volume method and generalized coordinates for the Cauchy boundary condition

This paper proposes a numerical solution for the diffusion equation with convective boundary condition applied to solids obtained through the revolution of arbitrary bi-dimensional geometries, using generalized coordinates. The diffusion equation was discretized using the finite volume method, with a fully implicit formulation. The solution exploits symmetry conditions and that decreases the computational effort demanded, in comparison to the traditional use of three-dimensional grids. The proposed solution was used to describe diffusion processes which have a well-known solution. There was a good agreement among the results obtained through the proposed solution and the correspondent analytical solutions, as well as the experimental data.     

Carbon steel corrosion inhibition in hydrochloric acid solution using a reduced Schiff base of ethylenediamine

The behavior of the Schiff base N,N′-bis(salicylidene)-1,2-ethylenediamine (Salen), its reduced form (N,N′-bis(2-hydroxybenzyl)-1,2-ethylenediamine) and a mixture of its preceding molecules, ethylenediamine and salicylaldehyde, as carbon steel corrosion inhibitors in 1 mol L⁻¹ HCl solution was studied by corrosion potential measurements, potentiodynamic polarization curves, electrochemical impedance spectroscopy and spectrophotometry measurements. The experimental results showed that the reduced Salen presented the highest efficiency among the inhibitors studied. The results obtained in the presence of Salen were similar to those obtained in the presence of the salicylaldehyde and ethylenediamine mixture, showing that in acid medium the Salen molecule undergoes hydrolysis, regenerating its precursor molecules.     

TiO<Subscript>2</Subscript> type influences fibronectin adsorption

Human fibronectin (FN) plays a key role in the biointegration of implants as the success depends on adsorption of proteins like FN [1]. Indeed FN can be an intermediary between the biomaterial surface and cells. The adsorption of human fibronectin (FN) on commercially pure titanium with a titanium oxide layer formed in a H₂O₂ solution (TiO₂ cp) and TiO₂ sputtered on Si (TiO₂ sp) was studied. Adsorption isotherms and the work of adhesion were assessed by wettability studies, X-ray photoelectron spectroscopy (XPS), and by radiolabelling of FN with ¹²⁵I, ¹²⁵I-FN. Exchangeability of bound FN by free FN, was also evaluated by the radiolabelling technique. Contact angle determinations have shown that FN displays higher affinity for the TiO₂ cp surface than for the TiO₂ sp. As expected from the surface free energy values, the work of adhesion of FN is higher for the TiO₂ cp substrate, the more hydrophilic one, and lower for the TiO₂ sp substrate, the more hydrophobic one. The adsorption isotherms were evaluated by two different techniques: radiolabelling of FN (¹²⁵I-FN) and XPS. TiO₂ cp adsorbs more FN than the TiO₂ sp surfaces as shown by the radiolabelling data. FN molecules are also more strongly attached to the former surface as indicated by the work of adhesion and by the exchangeability studies. Results using ¹²⁵I-FN also suggests that FN adsorbs as a multilayer for FN concentrations in solution higher than 100 μg/mL.     

Changes in particle area measurements due to SEM accelerating voltage and magnification

Scanning electron microscopy (SEM) images of polymer blends followed by digital image analysis is a rapid and easy method for the measurement of particle size and dispersion. The particle size determination is done with appropriate off-line image analysis software. However, it is necessary to understand how machine parameters involved in the formation of the SEM image influence area measurements of morphological features. In this work, the influence of the accelerating voltage used during image acquisition was examined with standard samples and with polymer blend samples. A systematic study centered on two mutually exclusive assumptions of area variation or no area variation with accelerating voltage was carried out. The off-line image analysis software was then calibrated according to the assumptions. The main conclusion of this study was that kV has an important influence on area measurement in SEM images. This effect was observed for different standard materials (metallic and polymeric) and for the range of magnifications used. The higher the accelerating voltages, the greater the error at high magnification for polymer samples. As the beam energy increases, the primary electrons penetrate more deeply into the solid specimen, producing low-resolution signals. These signals degrade the image and surface details, which became less well defined. Therefore, images of polymer samples must be taken at lower accelerating voltages so the desired surface details can be imaged clearly. To avoid area measurement errors, particle measurement must be done with the calibration of the off-line image analysis software corresponding to the accelerating voltage and magnification used for the acquired images.     

Application of semiclassical and geometrical optics theories to resonant modes of a coated sphere

This work deals with some aspects of the resonant scattering of electromagnetic waves by a metallic sphere covered by a dielectric layer, in the weak-absorption approximation. We carry out a geometrical optics treatment of the scattering and develop semiclassical formulas to determine the positions and widths of the system resonances. In addition, we show that the mean lifetime of broad resonances is strongly dependent on the polarization of the incident light.     

Recovery of cytomegalovirus and herpes simplex virus from upper and lower genital tract specimens obtained from women with pelvic inflammatory disease

Lower genital tract specimens and endometrial biopsies from 147 women with pelvic inflammatory disease (PID) and surgical specimens (fallopian tubes, ovaries, or both) from 22 women with PID and 37 women without PID were cultured for cytomegalovirus (CMV) and herpes simplex virus (HSV), as well as for organisms commonly associated with PID. CMV was isolated from 39 cervical or endometrial samples from 30 (20.4%) of 147 women with PID and from ovaries or fallopian tubes from 5 (22.7%) of 22 women with PID, but CMV was not recovered from surgical specimens obtained from 37 women undergoing surgery for tubal ligation, ectopic pregnancy, or other gynecologic conditions (P = .005). HSV was isolated from cervical samples obtained from 5 (3.4%) of 147 women with PID but not from any endometrial or surgical specimens. These data suggest that CMV, but not HSV, may contribute to the pathogenesis of PID in some patients.     

Electrochemistry of AISI 316L stainless steel in calcium phosphate and protein solutions

The influence of calcium phosphate and serum on the corrosion resistance of AISI 316L stainless steel in 0.9% NaCl solution was investigated. Both substances are responsible for an increase in the pitting corrosion resistance. Calcium phosphate accelerates the rate of film formation, enhances the release of iron and nickel, and retards that of chromium from a corroding surface. Proteins induce the incorporation of phosphorus and calcium in corrosion products. These effects appear to replicate the accumulation of the same elements observed on stainless steels corrodedin vivo.