FTIR and SEM analysis of polyester‐ and epoxy‐based composites manufactured by VARTM process

Polyester‐ and epoxy‐based composites containing glass and carbon fibers were manufactured using a vacuum‐assisted resin transfer molding (VARTM) process. Fourier transform infrared (FTIR) spectroscopy analyses were conducted to determine the interaction between fibers and matrix material. The results indicate that strong interaction was observed between carbon fiber and epoxy resin. However, weak interactions between remaining fiber‐matrix occur. Scanning electron microscopy (SEM) analysis was also performed to take some information about strength of interaction between fibers and matrix material. From SEM micrographs, it is concluded that the findings in SEM analysis support to that obtained in FTIR analysis. Another aim of the present work was to investigate the influence of matrix on composite properties. Hence, the strengths of composites having same reinforcement but different matrix systems in axial tension and transverse tension were compared. Short beam shear test has been conducted to characterize the interfacial strength in the composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Removal of boron from aqueous solution by adsorption on Al2O3 based materials using full factorial design

This paper aims the adsorption of boron from aqueous solution onto Siral 30 and Pural using 2³ full factorial design. The effect of individual variables and their interactional effects for boron adsorption were also determined. From the statistical analysis, it is inferred that as pH and temperature increased boron adsorption from aqueous solution decreased. Siral 30 was found to be more efficient adsorbent than Pural. The unimportant factor affecting boron adsorption from aqueous solution was also verified by using Fisher adequacy test. At the 90% confidence level, the type of adsorbent, temperature and type of adsorbent–temperature interaction was effective on boron adsorption from aqueous solution. The experimental results were fitted to the Langmuir, Freundlich and Dubinin–Radushkevich (DR) equations to find out adsorption capacities. In most cases, the results indicate that Freundlich and DR equations are well described with the sorption data. The adsorption capacity values of Siral 30 calculated from Freundlich and DR equation was greater than that of Pural. The thermodynamic parameters were also estimated and the adsorption process was not spontaneous nature.     

Sorption of malachite green on chitosan bead

Chitosan bead was synthesized for the removal of a cationic dye malachite green (MG) from aqueous solution. The effects of temperature (303, 313 and 323 K), pH of the solution (2-11) on MG removal was investigated. Preliminary kinetic experiment was carried out up to 480 min. The sorption equilibrium was reached within 5 h (300 min). In order to determine the adsorption capacity, the sorption data were analyzed using linear form of Langmuir and Freundlich equation. Langmuir equation showed higher conformity than Freundlich equation. Ninety-nine percent removal of MG was reached at the optimum pH value of 8. From kinetic experiments, it was obtained that sorption process followed the pseudo-second-order kinetic model. This study showed that chitosan beads can be excellent adsorbents at high pH values. Activation energy value for sorption process was found to be 85.6 kJ mol(-1). This indicates that sorption process can be assumed as chemical process. Due to negative values of Gibbs free energy, sorption process can be considered as a spontaneous. In order to determine the interactions between MG and chitosan bead, FTIR analysis was also conducted.     

Synthesis of chitosan beads as boron sorbents

Parameters, such as pH, temperature, initial boron concentration, adsorbent dosage, and ionic strength, affecting boron adsorption onto chitosan beads were examined in this study. The following values were obtained as the optimum conditions in our studied ranges: pH 8.0, temperature = 308 K, amount of chitosan beads = 0.15 g, initial boron concentration = 4 mg L⁻¹, and ionic strength = 0.1 M NaCl]. The adsorption kinetics were also examined in terms of three kinetic models: the pseudo‐first‐order, pseudo‐second‐order, and intraparticle diffusion models. The pseudo‐second‐order kinetic model showed very good agreement with the experimental data. Intraparticle plots seemed to have two steps and indicated multilinearity. Equilibrium data were evaluated with nonlinear and linear forms of the Langmuir and Freundlich equations. The experimental data conformed to the Freundlich equation on the basis of the formation of multilayer adsorption. To characterize the synthesized chitosan beads, we used Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) analyses. As shown by FTIR analysis, the boron species may have interacted with the NH₂ groups on chitosan. Microparticles of about 5 μm appeared in the SEM micrographs of the chitosan beads. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and characterization of poly(acrylic acid)/pillared clay superabsorbent composite

Pillared clay-based superabsorbents (PILC-SA) were synthesized by using Al pillared-montmorillonite K10 and KSF via graft copolymerization reaction of acrylic acid (AA). Swelling behavior of pillared clay-based superabsorbent films in distilled water and at different pH values were investigated at room temperature. It was also obtained that Al-KSF and Al-K10 based superabsorbents were pH dependent and showed a reversible swelling behavior. Water absorbency of Al-KSF based superabsorbent was higher than that of Al-K10 based one. SEM, FTIR, and XRD analysis were conducted for further characterization of the PILC-SA. FTIR analyses lead to ester formation between PILC and SA. XRD revealed the basal spacing of the pillared clays before and after in situ incorporation indicating that the morphology of the superabsorbent was exfoliated and the layers of clay dispersed on the composite.     

Dentin penetration of 2 calcium hydroxide combinations

OBJECTIVE: Calcium hydroxide is a common intracanal medicament. The powder can be mixed with different vehicles for placement in canals. This study examines pH changes in dentin with 2 different calcium hydroxide preparations. STUDY DESIGN: The combinations used were calcium hydroxide + distilled water and calcium hydroxide + glycerin (1/7 distilled water). One hundred forty extracted teeth with single canals were used. pH changes in dentin after the intracanal placement of these combinations were evaluated at different dentin thicknesses by measuring the pH of the external environment. RESULTS: For all dentin thicknesses and at all time periods, the calcium hydroxide + glycerin combination showed significantly higher pH values than the calcium hydroxide + distilled water combination. CONCLUSIONS: Considering pH elevations, we propose the use of a calcium hydroxide + glycerin combination.     

Development of Conductivity of Acrylic Polymer Using Ionic Liquids Incorporated with Zinc Oxide Nanoparticles

In this study, we synthesized antistatic and ultraviolet-resistant acrylic films with a combination of ionic liquids and ZnO nanoparticles for the prevention of static electricity and ultraviolet instability. ZnO and two different ionic liquids such as 1-ethyl-2,3-dimethylimidazolium ethyl sulfate and methyl-tri-n-butylammonium methylsulfate were preferred to achieve conductive and ultraviolet-resistant acrylic films. To obtain the highest ultraviolet protection factor and the lowest surface resistivity for the acrylic film, the combined effect of ZnO nanoparticles and the ionic liquids was utilized. The surface resistivity, thermal conductivity and effusivity, thermogravimetric analysis, and ultraviolet resistivity of the films were investigated. Surface morphology of the films and distribution of ZnO were also observed by scanning electron microscopy. The acrylic polymer exhibits higher ultraviolet resistance and lower transmission even in the low content of ZnO nanoparticles as compared with the neat polymer. The film consisting of methyl-tri-n-butylammonium methylsulfate ionic liquid showed the highest electrical conductivity performance even after 150 days. Consequently, ZnO nanoparticles are determined to be influential on ultraviolet-resistant properties, whereas ionic liquids are efficient on electrical conductivity performance of the acrylic polymer.     

Removal of malachite green by using an invasive marine alga Caulerpa racemosa var. cylindracea

The biosorption of a cationic dye, malachite green oxalate (MG) from aqueous solution onto an invasive marine alga Caulerpa racemosa var. cylindracea (CRC) was investigated at different temperatures (298, 308 and 318 K). The dye adsorption onto CRC was confirmed by FTIR analysis. Equilibrium data were analyzed using Freundlich, Langmuir and Dubinin-Radushkevich (DR) equations. All of the isotherm parameters were calculated. The Freundlich model gave a better conformity than Langmuir equation. The mean free energy values (E) from DR isotherm were also estimated. In order to clarify the sorption kinetic, the fit of pseudo-first-order kinetic model, second-order kinetic model and intraparticle diffusion model were investigated. It was obtained that the biosorption process followed the pseudo-second-order rate kinetics. From thermodynamic studies the free energy changes were found to be -7.078, -9.848 and -10.864 kJ mol(-1) for 298, 308 and 318 K, respectively. This implied the spontaneous nature of biosorption and the type of adsorption as physisorption. Activation energy value for MG sorption (E(a)) was found to be 37.14 kJ mol(-1). It could be also derived that this result supported physisorption as a type of adsorption.     

Equilibrium studies for trimethoprim adsorption on montmorillonite KSF

In this study, the adsorption of trimethoprim (TMP) on montmorillonite KSF was studied under different conditions (pH, ionic strength, temperature). The results indicate that a pH value of 5.04 is optimum value for the adsorption of TMP on KSF. The adsorption kinetics was interpreted using pseudo-first-order kinetic model, pseudo-second-order kinetic model and intraparticle diffusion model. The pseudo-second-order model provides the best correlation with the experimental data of KSF adsorption. The adsorption data could be fitted with Freundlich, Langmuir and Dubinin-Radushkevich equation to find the characteristic parameters of each model. It was found that linear form of Langmuir isotherm seems to produce a better model than linear form of Freundlich equation. From the Langmuir and Freundlich equation, the adsorption capacity values raised as the solution temperature decreased. From DR isotherm, it was also determined that the type of adsorption can be considered as ion-exchange mechanism. Determination of the thermodynamic parameters DeltaH(0), DeltaS(0) and DeltaG(0) showed that adsorption was spontaneous and exothermic in nature. It was also added that adsorption of TMP by KSF may involve physical adsorption.