Effect of silanized silica nanofiller on tack and green strength of selected filled rubbers

BACKGROUND: Tack and green strength of filled and gum (unfilled) natural rubber (NR), poly(styrene‐co‐butadiene) rubber (SBR), polybutadiene rubber (BR) and (SBR‐BR) blend with different loadings of reinforcement agent, silanized silica nanofiller (Coupsil 8113), were studied and the results compared and discussed. RESULTS: It was found that silica was fully dispersed in rubber matrix after 13 min of mixing. In addition, with some exceptions for NR and (SBR‐BR) blend, filler loading decreased the tack strength of the studied filled rubbers. Green strength and Mooney viscosity increased with filler loading for all studied filled rubbers but with different rates and amounts. The optimum filler loadings for NR and (SBR‐BR) filled blend were 30 and 10 phr, respectively. Tacks of NR filled rubbers were much higher than those of synthetic filled rubbers. CONCLUSION: It was concluded that filler loading alters substantially the tack and green strength of the rubbers under investigation. Copyright © 2009 Society of Chemical Industry     

Conductive wool yarns by continuous vapour phase polymerization of pyrrole

Conducting polypyrrole (PPy) coated wool yarns were prepared by a continuous vapour polymerization technique, using a speed of 1 m/min with different iron(III) chloride (FeCl₃) as the oxidant at different concentrations. The resistivities, tensile properties, longitudinal and cross-sectional views of PPy-coated wool yarns were investigated. Optimum specific electrical resistances of 2.96 Ω g/cm² at 80 g/L FeCl₃ and 1.69 Ω g/cm² at 70 g/L FeCl₃ were obtained for 500 and 400 twist per meter (TPM) yarns, respectively. PPy-coated wool yarns exhibited higher elongation than uncoated yarns. Longitudinal and cross-sectional views of the yarns indicate that PPy coating penetrated deep into the yarn cross-section and a uniform coating was obtained on the surface of the yarn surface.     

Optimization of the water-based road-marking paint by experimental design, mixture method

The main purpose of this research is formulating and optimizing a new road-marking paint which is an environmentally friendly product. This paint is produced with an emulsion of an acrylic copolymer and contains the least of the volatile organic compounds. The formulation and optimization procedure is carried out on the base of experimental design by the method of mixture in which the important paint properties are modeled by using special cubic model. The present method has the capability of investigation the effect of raw materials at different levels with fewer experiments than factorial and fractional factorial design.

In this research, the main parameters such as resin, pigment and filler were selected at different levels, and different samples were prepared by combination of additives and other required reagents. The properties of wet and dry films of the samples were determined using ASTM test methods. Different responses such as pigment volume concentration (PVC), latex critical pigment volume concentration (LCPVC), abrasion resistance, hardness, gloss, no pick up time and surface drying time, were selected as the objective functions of this study. By running DX6 software, using special cubic model and selection of desired range of end-use properties, the region of optimum paint formula was determined.

The accuracy of the model was examined by preparing a sample in optimized region and by determining its final properties, experimentally. The results exhibit a good agreement between the model and experimental measurements. This product was compared with commercial solvent based traffic paint and good quality was reported in end-use properties.     

A game equilibrium model of a retail electricity market with high penetration of small and mid-size renewable suppliers

Game theory has provided a practical tool to model players' strategic behavior in electricity markets, particularly as the world moves towards a more competitive market. A game theoretic approach can be used to find the clearing electricity price in a retail electricity market with a high penetration of small and mid-size renewable suppliers.     

Evaluating the effect of waste material on viscoelastic characteristics of bitumen

In this research, adding waste plastics (LDPE) and crumb rubber to bitumen causes the improvement in the viscoelastic behavior of bitumen. The sample containing 3% waste LDPE and 3% CR is the optimum one, which can be resulted from the complex modulus and the phase difference results. In continuance, elastic recovery test at 25 °C was performed on samples, and it was seen that with increase of crumb rubber content, elastic recovery increases because of elastic property of crumb rubber. In sample containing 5% waste polyethylene and 3% crumb rubber elastic recovery has been approached to the desirable amounts according to existence of enough crumb rubber. Finally, for evaluation of bitumen performance in mixture with modifiers, rotational viscosity on samples was performed.     

Synthesis and Microwave Dielectric Properties of SrLa4−x Pr x Ti5O17 (0 ≤ x ≤ 4) Ceramics

Single-phase ceramics in the SrLa_4?x Pr _x La₄Ti₅O₁₇ (0 ≤ x ≤ 4) series were processed via a solid-state sintering route. X-ray diffraction analysis revealed single-phase ceramics for all the compositions. The molar volume (V _m) decreased while the theoretical density (ρ _th) increased with increase in the Pr content. Substitution of Pr³⁺ decreased the relative permittivity (ε _r) and temperature coefficient of resonant frequency (τ _f) due to its smaller ionic polarizability (α _d) and ionic radius than La³⁺. In the present study, ε _r ≈ 54.2, Q _u f ₀  ≈ 7935 GHz, and τ _f  ≈ ?20.3 ppm/°C were achieved for the composition with x = 2 (i.e., SrLa₂Pr₂Ti₅O₁₇).     

The role of fillers and sodium metabisulfite on drug release from aged polyox tablets

Polyethylene oxides (PEOs) are extensively used to control the release rate of drugs from matrices. Unfortunately, polyox polymers are prone to oxidation under high temperature and relative humidity. The aim of this study was to investigate the effect of sodium metabisulfite as an antioxidant to overcome the drug release changes from polyox matrices (PEO 301 and 303) when stored at 40?°C. The effect of different types of fillers (lactose, mannitol and dicalcium phosphate dihydrate) on stability of diltiazem HCl release profiles was also investigated. Generally, the presence of sodium metabisulfite stabilized the release of drug from PEO matrices stored at 40?°C for 8 weeks. Whilst the absence of metabisulfite caused an increase in drug release from polyox matrices when stored at 40?°C. The results indicate that all three concentrations (0.25, 0.5 and 1% w/w) of sodium metabisulfite were able to overcome structural changes of polyox samples hence stabilizing the drug release. The results also showed that the incorporation of fillers in polyox matrices reduced the sensitivity of drug release when stored at elevated temperature. This indicates that when these excipients were used there was no need to incorporate additional antioxidant. DSC results showed that there was no difference in the melting points of fresh polyox samples and aged polyox samples containing sodium metabisulfite, whereas the melting point of aged polyox samples without sodium metabisulfite were lower than fresh polyox samples. This indicates that the presence of metabisulfite is essential to stabilize polyox samples.     

Wettability Enhancement of SiCp in Cast A356/SiCp Composite Using Semisolid Process

The effects of SiCp treatment and magnesium addition on microstructural and mechanical properties of Al356/20 wt% SiCp semisolid composites were investigated. The results showed that cleaning and oxidizing of SiCp and addition of 1 wt% Mg resulted in improving wettability, incorporation, and uniform distribution of SiCp in A356 matrix. Consequently, the ultimate tensile strength (UTS) value increased by 19% and 32% when the SiC was treated and also when Mg was added, respectively, compared to as-received SiCp. In addition, hardness value increased from 69.7 HV in as-received SiCp to 94.8 HV after SiCp treatment and addition of Mg.     

Dual-Rotation Speed Friction Stir Welding: Experimentation and Modeling

Implementing differential rotation speeds of pin and shoulder in the friction stir welding process is considered. Experimental investigations were carried out using a newly designed and fabricated apparatus for dual-rotation speed friction stir welding. Metallographic studies demonstrated that appropriate selection of separate pin and the shoulder rotation speeds not only results in defect-free joints, but also affects the weld zone by controlling the heat input delivered. An energy model for predicting maximum temperature was extended to the dual-rotation speed friction stir process. The model was verified using the previous experimental results reported in the literature.     

Improving the quality of surface in polishing process with the magnetic abrasive powder polishing (MAPP) by use of ultrasonic oscillation of work-piece on a CNC table

In this research work, polishing inside, outside and over the cylindrical parts has been done by using a completely new and innovative method. The work-pieces have been placed on a two-axis Cartesian CNC Table for polishing operations. The Magnetic Rotary Head continuously changes its rotation direction from CW to CCW and CCW to CW and meanwhile the part begin to oscillate up-and-down under a High Frequency (20 kHz) conditions. The Frequency of changing direction From CW to CCW and CCW to CW is one of the important parameters in this method. This method is a kind of Ultrasonic Assisted Polishing (UAP) and novelty of this research work is combining this method with motion of work piece under CNC trajectory with continuously changing direction of Magnetic Rotary Head. Gap between Rotary Magnetic Polishing Head and the Work piece Surface can be controlled by a power transmission screw which operates in the direction of the vertical axis. Several experiments have proved high performance of this new proposed method in the process of polishing in short times.