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Abstract: High ion-exchange capacity (IEC) sulfonated polystyrene nanoparticles were synthesized by an emulsion copolymerization of styrene, divinyl benzene and sulfonated styrene (SS). The effects of varying the counterion of the sulfonated styrene monomer, the SS concentration, the surfactant and the addition of a crosslinking agent on the ability to stabilize the emulsion nanoparticles to high IEC were studied. Water-insoluble nanoparticles, 20–160 nm in diameter, with IEC as high as 5.2 meq/g were achieved using sulfonated styrene with a quaternary alkyl ammonium cation, a non-ionic surfactant and a crosslinking agent in the emulsion formulation. That IEC corresponds to fully sulfonated crosslinked polystyrene. [ABSTRACT FROM AUTHOR]

Abstract: Proton exchange membranes of sulfonated crosslinked polystyrene (SXLPS) particles dispersed in crosslinked poly(dimethyl siloxane) matrix were investigated. Three different sizes of particles—25, 8 and 0.08μm—were used at loadings from 0 to 50wt% and the influence of these variables on the water and methanol uptake and proton conductivity were observed. With the reduction in particle size in the composite membrane, more water or methanol uptake was observed. Three different states of water were revealed in the composite membranes by differential scanning calorimetry (DSC). The number of bound water molecules per SO3H group was 11–15 in membranes with 8- and 25-μm SXLPS. The ratio of bound to unbound water molecules was more than one in these membranes, whereas it was less than one in membranes with 0.08-μm SXLPS. The proton conductivities of the membranes increased with the increase in particle loading. At particle loadings above 35wt%, membranes containing 8-μm SXLPS had higher conductivity compared to 25-μm SXLPS at room temperature. The conductivity of membranes containing 0.08-μm SXLPS was restricted to 10−3 S/cm because of the inherently low IEC of the particles. Increasing the temperature from 30 to 80°C drastically enhanced the conductivity of the composite membranes compared to Nafion® 112. At 80°C, conductivities as high as 0.11±0.04S/cm were observed for membranes containing more than 30wt% of 25-μm SXLPS particles. [Copyright &y& Elsevier]

Describes the fabrication of a rheo-light scattering instrument for investigating the influence of shear on the phase behavior of polymer blends from a commercial parallel-plate rheometer. Projection of the laser light scattering; Angular velocities generated by the rheometer; Performance and accuracy of the light-scattering instrument.

Abstract: Various polymeric cable materials were aged in operating nuclear plants while exposed to a range of temperatures and radiation fluxes. Materials included ethylene propylene rubber (EPR), chlorosulfonated polyethylene (CSPE), crosslinked polyethylene (XLPE), and polychloroprene (CR) (also known by the brand name Neoprene®). Changes in density were monitored using the density-gradient method while changes in elongation-at-break were determined using strip specimens that were microtomed from the cable parts. For most cable jackets, the elongation-at-break shows a significant negative correlation with density in a power-law fashion. For some materials, the elongation-at-break versus density correlation can be described adequately by a simple linear model, a special case of the power-law model. Artificial (laboratory) aging typical of that used for qualification was also conducted on the same cable materials and correlations between density and elongation-at-break were similarly derived. For each material, the correlation obtained from artificial aging was then compared with that of natural aging to test the postulate that artificial and natural aging follow the same pattern. For some materials, the results show that there is a significant difference between these two aging formats. For all the cable materials that show correlation between these two material properties, the artificially aged specimens tend to have lower values of elongation-at-break than the naturally aged specimens within the density range common to both aging schemes. Thus, for these materials, the two aging methods are intrinsically different. [Copyright &y& Elsevier]

Presents a study which reported the results of numerical simulations for the change of both mechanical and electrical properties of anisotropically filled elastomers. Problem formulation and numerical simulation; Results and discussion; Conclusion.

Abstract: The importance of the blend microstructure and its effect on conductivity and structural integrity of proton exchange membranes (PEM) were investigated. Sulfonated poly(ether ketone ketone) (SPEKK) was selected as the proton-conducting component in a blend with either poly(ether sulfone) (PES) or SPEKK with a different sulfonation level. The second component was added to improve the mechanical stability in the fuel cell environment. Membranes were cast from solution using N-methyl-2-pyrrolidone (NMP) and dimethylacetamide (DMAc). Special attention was paid to the ternary solution behavior. Solution cast SPEKK/PES membranes are homogeneous for all studied compositions, 8/2 through 5/5 (w/w), and sulfonation levels, 1.7–3.5mequiv./g. Although this polymer pair does not show evidence for intrinsic compatibility, the excellent solvent quality results in a frozen-in structure during solution casting. The morphology of SPEKK/SPEKK blends can be tailor-made by finding the right balance between composition, casting solvent and temperature. Co-continuous morphologies can be devised for an SPEKK blend with sulfonation levels of 1.2 and 2mequiv./g. Both blends show lower swelling than the parent SPEKK. This results in better stability of PEMs during fuel cell testing. [Copyright &y& Elsevier]

Abstract: Human bone mineral contains calcium-deficient crystalline hydroxyapatite (HA) embedded in collagen fibers. Research over the past two decades has focused on preparing synthetic HA, which closely resembles bone apatite and exhibits excellent osteoconductivity. This paper describes the synthesis of nano-HA particles via a wet precipitation method. The concentration of the reactants (0.5, 1.0 and 2.0 g/dL) and the temperature of the reaction (25, 70 and 100 °C) were varied. FESEM images were used to determine the size and shape of the resulting nano-particles. The length and breadth of the HA particles were found to increase with the temperature, while the aspect ratio increased with both the concentration and the temperature. The average length of the particles was in the range 53–165 nm and the average breadth in the range 29–52 nm. Agglomerates of HA precipitates were formed during the synthesis process. HA precipitated at 25 °C and concentration 0.5 g/dL resulted in large agglomerates with a specific surface area of 79.8 m2/g. HA agglomerates synthesized at each condition were pressed into discs and sintered at 1200 °C. It was found that there was a positive correlation (p=0.015) between sintered density and biaxial flexural strength. A maximum strength of 57.4 MPa was observed for the specimens 2.0–70 which also attained the highest density, 92%. XRD results indicated that most of the sintered discs had slightly decomposed. The decomposition of the specimens and their resulting microstructures also contributed to the mechanical strength drop of the specimens. [Copyright &y& Elsevier]