Dynamic Mechanical Properties of Activated Carbon–Filled Epoxy Nanocomposites

Nano-activated carbons obtained from oil palm empty fiber bunch (AC-EFB), bamboo stem (AC-BS), and coconut shells (AC-CNS) were reinforced in epoxy matrix to fabricate epoxy nanocomposites. The dynamic mechanical analysis of epoxy nanocomposites was carried out, and 5% AC-CNS treated with KOH-filled epoxy composites displayed the highest storage modulus of all the activated carbon–filled epoxy composites. The incorporation of a small amount of AC-BS, AC-EFB, and AC-CNS to the epoxy matrix enhanced the damping characteristics of the epoxy nanocomposites. The 5% AC-EFB treated with H₃PO₄ filled epoxy composites showed the highest glass transition temperature (T_g) in all temperature ranges.     

Adsorption in columns packed with porous adsorbent particles having partially fractal structures

A mathematical model is constructed and solved that could describe the dynamic behavior of the adsorption of a solute of interest in single and stratified columns packed with partially fractal porous adsorbent particles. The results show that a stratified column bed whose length is the same as that of a single column bed, provides larger breakthrough times and a higher dynamic utilization of the adsorptive capacity of the particles than those obtained from the single column bed, and the superior performance of the stratified bed becomes especially more important when the superficial velocity of the flowing fluid stream in the column is increased to accommodate increases in the system throughput. This occurs because the stratified column bed provides larger average external and intraparticle mass transfer and adsorption rates per unit length of packed column. It is also shown that increases in the total number of recursions of the fractal and the ratio of the radii between larger and smaller microspheres that make up the partially fractal particles, increase the intraparticle mass transfer and adsorption rates and lead to larger breakthrough times and dynamic utilization of the adsorptive capacity of the particles. The results of this work indicate that highly efficient adsorption separations could be realized through the use of a stratified column comprised from a practically reasonable number of sections packed with partially fractal porous adsorbent particles having reasonably large (i) total number of recursions of the fractal and (ii) ratio of the radii between larger and smaller microspheres from which the partially fractal particles are made from. It is important to mention here that the physical concepts and modeling approaches presented in this work could be, after a few modifications of the model, applied in studying the dynamic behavior of chemical catalysis and biocatalysis in reactor beds packed with partially fractal porous catalyst particles.     

Enantioselective synthesis of anti-β-amido-α-hydroxy esters via asymmetric transfer hydrogenation coupled with dynamic kinetic resolution

The asymmetric transfer hydrogenation of β-amido-α-keto esters providing the corresponding anti-β-amido-α-hydroxy esters via dynamic kinetic resolution is reported. The use of a commercially available, or simply prepared, chiral ruthenium catalyst results in good yields as well as high diastereoselectivities and enantioselectivities.     

In–out asymmetry and interference effects in plasmon excitation by swift charged particles traversing a surface

We investigate the excitation of plasmons by a fast charged particle moving in the vicinity or traversing the surface of a solid along an arbitrary trajectory. We use both quantum‐mechanical and semiclassical dielectric formulations to study how the particle couples with the bulk and surface excitations. We pay special attention to the differences and similarities between incoming and outgoing trajectories, finding some novel oscillatory structures that can be ascribed to an interference effect between direct and reflected plasmon excitations. Copyright © 2013 John Wiley & Sons, Ltd.     

Ternary blends based on poly (ethylene-naphthalate)/glass fibers/nitrile rubber: Preparation,properties and effect of dynamic vulcanization

This work studied the possibility of utilizing nitrile rubber (NBR) to modify the impact properties of poly (ethylene-naphthalate) (PEN). The PEN/NBR ratio used changed from 100/0 to 60/40. At the same time, glass fibers (GF), 40% weight of the PEN component, were used to reinforce the blends to compensate for the loss of mechanical properties of PEN by incorporation of NBR. The results showed that the impact strength of the PEN/GF/NBR blend (PEN/NBR = 60/40) was increased up to 27.6J/m, nearly 5 times higher than that of the neat PEN. Meanwhile, the tensile strength and flexural strength were still maintained at as high as 66.1 MPa and 98.2 MPa, respectively. Dynamic vulcanization further improved the mechanical properties of the PEN/GF/NBR blends, which provided routes to the design of new PEN/elastomer blends. Other properties of the PEN/GF/NBR blends were also investigated in terms of morphology of fractured surface, dynamic mechanical behavior, thermal stability and crystallization, by scanning electron microscopy (SEM), dynamic mechanical analysis (DMA), thermo-gravimetric analysis (TGA) and differential scanning calorimetry (DSC), respectively.     

N‐methyl‐2‐pyrrolidonium methyl sulfonate acidic ionic liquid as a new dynamic coating for separation of basic proteins by capillary electrophoresis

A simple and economical CE method has been developed for the analysis of four model basic proteins by employing N‐methyl‐2‐pyrrolidonium methyl sulfonate ionic liquid (IL) as the dynamic coating material based on the interaction of both between electrostatic attraction and hydrogen bond, and between the organic cations of IL and the inner surface of bare fused‐silica capillary. The N‐methyl‐2‐pyrrolidonium‐based IL modified capillary not only generated a stable suppressed electroosmotic flow, but also effectively eliminated the wall adsorption of proteins. Several important parameters such as the IL concentration, pH values, and concentrations of the background electrolyte were optimized to improve the separation of basic proteins. Consequently, under the optimum separation conditions, a satisfied separation of basic proteins including lysozyme, cytochrome c, ribonuclease A, and α‐chymotrypsinogen A with theoretical plates ranging from 2.09 × 10⁵ to 4.48 × 10⁵ plates/m had been accomplished within 15 min. The proposed method first illustrated the effect of hydrogen bond between coating material and inner capillary surface on the coating, which should be a new strategy to design and select more effective coating materials to form more stable coatings in CE.     

MULTIPLE EMULSIONS STABILIZED BY COLLOIDAL MICROGRYSTALLINE CELLULOSE

Multiple emulsions stabilized by colloidal microcrystalline cellulose (CMCC, Avicel RC591) at the w/o and o/w interfaces, and by the addition of Span 80 or Span 85 at the w/o interface, were studied by means of brightfield microscopy, freeze-etch electron microscopy, droplet size distribution analysis and rheologic measurements. Stable multiple emulsions were prepared by incorporation of sodium chloride in the innermost aqueous phase, thereby creating an osmotic gradient preventing loss of the inner aqueous phase to the external aqueous phase. Freeze-etch electron microscopy of the multiple emulsions indicated the presence of a network of microcrystalline cellulose at the outer o/w interface. It may be assumed that the surfactant directly stabilized the w/o interface by adsorption at the interface, as well as indirectly by facilitating wetting of the microcrystalline cellulose by the oil. From rheologic measurements, the existence of a three-dimensional network in the external aqueous phase was indicated by the considerable degrees of thlxotropy and significant static yield values of these multiple emulsions.     

十二烷基硫酸钠水溶液的动态表面吸附性质

利用MPTC型气泡压力张仪研究了十二烷基硫酸钠(SDS)溶液在不同NaCl 浓度下的动态表面吸附性质, 分析了离子型表面活性剂在表面吸附层和胶束中形成双电层结构产生表面电荷对动态表面扩散过程和胶束性质的影响. 结果表明, SDS在表面吸附过程中, 表面电荷的存在会产生5.5 kJ·mol^-1的吸附势垒(E_a), 显著降低十二烷基硫酸根离子(DS^-)的有效扩散系数(D_eff). 十二烷基硫酸根离子的有效扩散系数与自扩散系数(D)的比值(D_eff/D)仅为0.013, 这表明SDS与非离子型表面活性剂不同, 在吸附初期为混合动力控制吸附机制. 加入NaCl可以降低吸附势垒. 当加入不小于80 mmol·L^-1 NaCl后, E_a小于0.3 kJ·mol^-1, D_eff/D在0.8-1.2之间, 表现出与非离子型表面活性剂相同的扩散控制吸附机制. 同时, 通过分析SDS胶束溶液的动态表面张力获得了表征胶束解体速度的常数(k₂). 发现随着NaCl 浓度的增大, k₂减小, 表明SDS胶束表面电荷的存在会增加十二烷基硫酸根离子间的排斥力, 促进胶束解体.