Effects of Nanoparticles on Film Properties of Waterborne Acrylic Emulsions

Waterborne acrylic emulsion was obtained by using methyl methacrylate, ethyl and butyl acrylate monomers. Emulsions containing nanoparticles were prepared by blending the stable dispersions containing SiO₂ or MMT nanoparticles. The films were prepared from emulsions and coating tests were applied. The physical properties of prepared emulsions are better than the commercial emulsions. The addition of the nanoparticles especially SiO₂ have positive effect on the resistance to environmental conditions of emulsions. Waterborne acrylic emulsions containing nanoparticles prepared in this study can be used in the manufacturing of the semi-lustrous emulsion type nano paint with low cost, high performance and environmentally friendly.     

Analysis of Physical and Thermodynamic Properties of Poly(2-Phenyl-1,3-Dioxolane-4-Yl-Methyl-Methacrylate-Co-Styrene) Polymer with Inverse Gas Chromatography

In this study, physical and thermodynamic properties of poly(2-phenyl-1,3-dioxolane-4-yl-methyl-methacrylate-co-styrene) (PDMMA-ST) were investigated by using inverse gas chromatography. Two groups of solvents with different chemical natures and polarities were used to obtain information about PDMMA-ST-solvent interactions: alcohols and alkanes. The specific retention volume (V_g ⁰), the sorption enthalpy (ΔH₁ ^S), sorption free energy (ΔG₁ ^S), sorption entropy (ΔS₁ ^S), the weight fraction activity coefficients of solute probes at infinite dilution (Ω ₁ ^∞), and Flory-Huggins interaction parameters (χ ₁₂ ^∞) between polymer and solvents were determined for the interactions of PDMMA-ST with alcohols and alkanes by inverse gas chromatography in the temperature range of 333–473 K. Also, the solubility parameters of PDMMA-ST at infinite dilution were found by plotting the graph of [(δ ₁ ²/RT) - χ ₁₂ ^∞/V₁] versus solubility parameters, δ ₁, of probes.     

COLOR CHANGE KINETICS OF CELERY LEAVES UNDERGOING MICROWAVE HEATING

The aim of this study was to investigate the effect of microwave output power and sample amount on color change kinetics of celery leaves (Apium graveolens L.) during microwave heating. The color parameters of the materials were quantified by the Hunter Lab system. These values were also used for calculation of the total color change, chroma, hue angle, and browning index. The microwave heating process changed color parameters of L, a, and b, causing a color shift towards darker region. The mathematical modeling study of color change kinetic showed that L, a, b, and chroma fitted to a first-order kinetic model, while total color change (ΔE), hue angle, and browning index (BI) followed a zero-order kinetic model. For calculation of the activation energy for color change kinetic parameters, the exponential expression based on the Arrhenius equation was used.     

Evaluation of antibacterial effects of contemporary orthodontic bonding materials

Aim: The aim of this study was to evaluate the antibacterial effects of five orthodontic bonding materials commonly used in orthodontics. Materials and Methods: The antibacterial effects of five orthodontic bonding materials were evaluated against Streptococcus mutans and Streptococcus salivarius by direct contact test (DCT). Using the DCT technique, quintet specimens of Transbond XT, Blugloo, Grengloo, Light Bond, and Opal Bond were applied to the bottom and the walls of the five wells of a 96-microtiter plate with a height of 2 mm. Samples were prepared in two sets: 1-day samples and 7-day samples. Ten microliters of bacterial suspension were added to each well for direct contact with each material for 1h at 37 °C. Bacterial growth was then measured in a microplate spectrophotometer hourly at 600 nm for 24 h. Five uncoated wells with identical inoculum sizes served as positive controls. The data obtained at the end of 24 h was statistically analyzed with one-way ANOVA, and post hoc comparisons were done using Tamhane’s T2 test. Results: Blugloo generally showed better antibacterial activity than the other materials. Transbond XT did not show any antibacterial activity. There was a statistically significant difference between Transbond XT and Light Bond in the 1-day sample against S. mutans (p < 0.05). No statistically significant differences were found among the other groups (p > 0.05). Conclusion: Blugloo had the most potent antibacterial activity against S. salivarious.     

Increasing single-lap joint strength by adherend curvature-induced residual stresses

Single-lap joint (SLJ) geometry is the most widely used type of adhesive joint geometry. In this joint, peel stresses occur at the overlap ends due to load eccentricity and the presence of shear-free adhesive termination surfaces. These peel stresses, along with the transverse tensile stresses which occur along the overlap longitudinal axes, and adhesive shear stresses, ultimately cause joint failure. Obviously, reductions in these stresses should result in higher joint strength and increased load capacity. To this end, we exploited elastic spring-back capability of (steel) metal adherends by initially forming curved segments of varying arc lengths and radii at overlap ends. These adherends with curved-end sections were then bonded in single-lap configuration, simply by applying sufficient bonding pressure to elastically flatten the curved segments to result in typically flat overlap sections subsequent to adhesive cure and the removal of bonding pressure. Since the elastic adherend overlap ends tend to revert back to their initial curved form, they exert compressive residual stresses on the adhesive layer in the overlap end regions. We determined that the compressive residual stresses induced in this fashion considerably increased the load capacity of SLJs subjected to tension.     

Cellulose templating method for the preparation of La0.8Sr0.2Ga0.83Mg0.17O2.815 (LSGM) solid oxide electrolyte

La_0.8Sr_0.2Ga_0.83Mg_0.17O_2.815 (LSGM) materials are synthesized with a fast and facile cellulose templating method for the first time and characterized by XRD, EIS, Archimedes method and SEM–EDS. LSGM powders with a phase purity of 91.7 mol% are obtained after the calcination at 1300 °C for 12 h. SEM–EDS results indicate possible decomposition and reconstruction of the LSGM phase due to the diffusion of Sr-rich species to the grain boundaries for the sample sintered at 1500 °C for 6 h. Maximum conductivity value is found to be 4.2 × 10^?2 S cm^?1 at 800 °C for the sample calcined at 1300 °C for 12 h and sintered at 1400 °C for 6 h. Phase purity, stability and relative density are the important factors for obtaining high performance LSGM electrolytes. Therefore, cellulose templating method is a promising candidate for the preparation of LSGM electrolytes.     

The ratio of crystallinity and thermodynamical interactions of polycaprolactone with some aliphatic esters and aromatic solvents by inverse gas chromatography

Summary The retention diagrams of benzene, toluene, ethyl benzene, chloro benzene, n-propyl benzene, isopropyl benzene, methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate and isoamyl acetate on the polycaprolactone were plotted at temperatures between 70 and 140^oC by inverse gas chromatography technique. Percent crystallinity of polycaprolactone were obtained at temperatures below melting point from the retention diagrams of benzene, toluene and ethyl benzene. It was concluded that the data obtained by inverse gas chromatography were comparable those of obtained by differential scanning calorimetry. Specific retention volume, V_g^o, Flory-Huggins polymer-solvent interaction parameters, ₁₂, the weight fraction activity coefficients of the solvents at infinite dilution, ₁, effective exchange energy parameters, X_eff were determined. Later, the partial molar heat of sorption, H_1,sorp and the partial molar heat of mixing, H₁ were obtained from the slope of the logarithm of specific retention volume, Ln V_g^o versus 1/T plot and from the slope of the logarithm of the weight fraction activity coefficients, ₁versus 1/T plot, respectively.     

Synthesis and characterization of water-based poly(vinyl acetate-co-butyl acrylate) latexes containing oligomeric protective colloid

Poly(vinyl acetate-co-butyl acrylate) latexes having oligomeric N-methylol acrylamide were prepared by semi-continuous emulsion polymerization. The effects of new protective colloid and comonomer ratios on the physicochemical and colloidal properties of latexes were investigated. The changes in homopolymer and copolymer latexes were determined by measuring viscosity, particle size, molecular weight (MW), molecular weight distribution (MWD), and surface tension. [`(M)]<sub>n</sub> \bar{M}_{n} values of copolymer latexes were found to be lower than the MWs of the poly(vinyl acetate) and poly(butyl acrylate) homopolymers. In general, [`(M)]_n \bar{M}_{n} and [`(M)]_\textw \bar{M}_{\text{w}} values of copolymer latexes changed irregularly with increasing BuA ratio in the copolymer composition.     

Characterization of Terebinth Fruit Oil and Optimization of Acidolysis Reaction with Caprylic and Stearic Acids

Characterization of the fatty acid and triacylglycerol composition of terebinth fruit oil and the synthesis of structured lipids (SL) were performed in this study. Interesterification reaction of terebinth fruits oil (Pistacia terebinthus L.) with caprylic acid (CA) and stearic acid (SA) to produce a SL was performed in n-hexane using immobilized sn-1,3 specific lipase from Mucor miehei. The effect of reaction conditions and relationship among them were analyzed by response surface methodology (RSM) with a four-factors five-level central composite rotatable experimental design. The four major factors chosen were enzyme load (10–30 wt% based on substrates), reaction time (7–18 h), reaction temperature (40–60 °C) and substrate mole ratio (terebinth oil:SA:CA 1:1:1–1:1:3). The best fitting quadratic model was determined by regression and backward elimination. Based on the fitted model, the optimal reaction conditions for the incorporation of CA and SA were found to be temperature 50 °C; time 18 h; enzyme load 30 wt%; substrate ratio 1:1:3. Under these optimum conditions, the incorporation of SA and CA could be obtained as 19 and 14%, respectively.