Equilibrium and kinetic studies of the extraction of chelated copper(II) anions with Aliquat 336

The equilibrium and kinetics of solvent extraction of Cu²⁺ from aqueous solutions containing equimolar EDTA with Aliquat 336 in n‐decanol and kerosene at 298 K were investigated. The concentrations of Cu²⁺ (8–50 mol m^?3), Cl^? (5–60 mol m^?3), and Aliquat 336 (20–100 mol m^?3) were varied. A semi‐empirical model with three parameters was proposed to describe the equilibrium behavior, in which the non‐idealities in both aqueous and organic phases were considered. Over the ranges studied, the model agreed reasonably well with the experimental data (standard deviation, 15%). The forward and backward reaction rate constants were determined as (5.31 ± 0.16)×10^?6 m^9/4 mol^?3/4 s^?1 and (2.62 ± 0.09)×10^?7 s^?1, respectively, at 298 K. An interfacial reaction mechanism was proposed, which revealed that the reaction between the chelated anions and trimeric amine molecules at the interface was rate limiting. The derived rate laws were consistent with the experimental results. © 2002 Society of Chemical Industry     

Interactions of Impact Shock Waves in a Thin-Walled Explosive Container. II. Impact by a Cone-Nosed Projectile

Interaction of impact shock waves that could detonate an explosive (Composition B) confined in a thin-walled container impacted by a cone-nosed projectile is numerically studied, based on the Forest Fire explosive reaction rate model. The normal impact on the container by a small projectile with a conical nose is considered. Depending on the cone angle of the nose part of the projectile, the zone of interaction of initiating shock waves can be remote from the central axis of the impact. The off-the-central-axis detonation is interpreted from the viewpoint of different interaction modes in the explosive container, which are reflected from the cassette wall, change their directions, and superimpose onto each other, leading to explosive detonation.     

Catalytic degradation of waste polyolefinic polymers using spent FCC catalyst with various experimental variables

Liquid-phase catalytic degradation of waste polyolefinic polymers (HDPE, LDPE, PP) over spent fluid catalytic cracking (FCC) catalyst was carried out at atmospheric pressure with a stirred semi-batch operation. The effect of experimental variables, such as catalyst amount, reaction temperature, plastic types and weight ratio of mixed plastic on the yield and accumulative amount distribution of liquid product for catalytic degradation was investigated. The initial rate of catalytic degradation of waste HDPE was linearly increased with catalyst amount (4-12 wt%), while that was exponentially increased with reaction temperature (350-430 ‡C). Spent FCC catalyst in the liquid-phase catalytic degradation of polymer was not deactivated fast. The product distribution from catalytic degradation using spent FCC catalyst strongly depended on the plastic type. The catalytic degradation of mixed plastic (HDPE: LDPE: PP: PS=3: 2: 3: 1) showed lower degradation temperature by about 20 ‡C than that of pure HDPE.     

Novel CO2 Absorbents Using Lithium-Containing Oxide

We have discovered a series of lithium-containing oxides that immediately react with ambient carbon dioxide (CO₂) up to 700°C. The products react and return reversibly to the oxides at a temperatures higher than about 700°C. The absorption capacity surpasses that of other CO₂ absorbents by a factor of 10. Utilizing these absorbents, the possibility of a CO₂ separation system that operates at around 500°C is proposed. It is generally believed that a CO₂ separation process operable at temperatures higher than 500°C has the special benefit of a small energy penalty. Moreover, the absorption also proceeds at ambient temperature in the atmospheric environment. This property offers the possibility of many other applications, such as air cleaners or cartridges. Therefore, we think these materials have the potential to make a valuable contribution to the realization of CO₂ emission control.     

Solution copolymerization of methyl methacrylate and alkyl methacrylates in a continuous stirred tank reactor(CSTR)

Continuous solution copolymerization of methyl methacrylate with ethyl methacrylate or n-butyl methacrylate was carried out in a continuous stirred tank reactor. Solvent and initiator used were toluene and benzoyl peroxide, respectively. Reaction volume was 1.2 litters, residence time 3 hours and polymerization temperature 80°C. The copolymerization conversions were analyzed by UV spectrophotometry and confirmed by measuring the solid weights of copolymers obtained after evaporating solvent. The copolymerization of methyl methacrylate and alkyl methacrylates followed the second order kinetics. The simulated conversions and copolymerization rates were compared with the experimental results. The average time to reach dynamic steady-state was three and half times of the residence time.     

Glass transition and mechanical properties of PLLA and PDLLA‐PGA copolymer blends

The change of the glass transition temperatures (T_g) in the blend of poly(L ‐lactic acid) (PLLA) and the copolymers of poly(D,L ‐lactic acid) and poly(glycolic acid) (PDLLA‐PGA) with different D,L ‐lactic acid and glycolic acid composition ratio (50 : 50, 65 : 35, and 75 : 25) was studied by DSC. Dynamic mechanical measurement and tensile testing were performed at various temperatures around T_g of the blend. In the blend of PLLA and PDLLA‐PGA50 (composition ratio of PDLLA and PGA 50 : 50), T_g decreased from that of PLLA (about 58°C) to that of PDLLA‐PGA50 (about 30°C). A single step decrease was observed in the DSC curve around T_g between the weight fraction of PLLA (W(PLLA)) 1.0 and 0.7 (about 52°C) but two‐step changes in the curve are observed between W(PLLA) = 0.6 and 0.3. The T_g change between that of PLLA and that of PDLLA‐PGA and the appearance of two T_gs suggest the existence of PLLA rich amorphous region and PDLLA‐PGA copolymer rich amorphous region in the blend. A single step decrease of E′ occurs at around T_g of the pure PLLA but the two‐step decrease was observed at W(PLLA) = 0.6 and 0.4, supporting the existence of the PLLA rich region and PDLLA‐PGA rich region. Tensile testing for various blends at elevated temperature showed that the extension without yielding occurred above T_g of the blend. Partial miscibility is suggested for PLLA and PDLLA‐PGA copolymer blends. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2164–2173, 2004     

Damage zone development in PVC under a multiaxial tensile stress state

The irreversible deformation mechanisms of poly(vinyl chloride) with a semicircular notch under slow tensile loading have been studied as a function of sheet thickness. Initially, core yielding was observed in the optical microscope as two families of slip lines growing from the notch surface in the centre of the specimen. The size and shape of the core yielding zone could be described by plasticity analysis. A stress-whitened zone subsequently initiated near the tip of the slip line zone. The stress whitening was caused by 1 m voids that were visible in the scanning electron microscope. The mean stress for stress whitening was calculated to be 43.0±1.5 MPa by a plastic stress analysis of a pressure-dependent yield material. By assuming a constant mean stress along the boundary of the stress-whitened zone, the one-dimensional shift of the elastic stress distribution was obtained. At higher stresses, hinge shear and intersecting shear were observed for thick and thin sheet, respectively.     

Constructing confidence intervals of extreme rainfall quantiles using Bayesian,bootstrap, and profile likelihood approaches

Hydrological risk is highly dependent on the occurrence of extreme rainfalls.This fact has led to a wide range of studies on the estimation and uncertainty analysis of the extremes.In most cases,confidence intervals(CIs)are constructed to represent the uncertainty of the estimates.Since the accuracy of CIs depends on the asymptotic normality of the data and is questionable with limited observations in practice,a Bayesian highest posterior density(HPD)interval,bootstrap percentile interval,and profile likelihood(PL)interval have been introduced to analyze the uncertainty that does not depend on the normality assumption.However,comparison studies to investigate their performances in terms of the accuracy and uncertainty of the estimates are scarce.In addition,the strengths,weakness,and conditions necessary for performing each method also must be investigated.Accordingly,in this study,test experiments with simulations from varying parent distributions and different sample sizes were conducted.Then,applications to the annual maximum rainfall(AMR)time series data in South Korea were performed.Five districts with 38-year(1973–2010)AMR observations were fitted by the three aforementioned methods in the application.From both the experimental and application results,the Bayesian method is found to provide the lowest uncertainty of the design level while the PL estimates generally have the highest accuracy but also the largest uncertainty.The bootstrap estimates are usually inferior to the other two methods,but can perform adequately when the distribution model is not heavy-tailed and the sample size is large.The distribution tail behavior and the sample size are clearly found to affect the estimation accuracy and uncertainty.This study presents a comparative result,which can help researchers make decisions in the context of assessing extreme rainfall uncertainties.     

Spatial distribution of silica fillers in phase-separated rubber blends investigated by three-dimensional elemental mapping

The distribution of nano-sized silica in binary rubber blends is characterized by scanning transmission electron microscopy (STEM) tomography combined with energy dispersive X-ray spectrometry (EDX). 3D distribution of silica is visualized by STEM-EDX tomography with the tilt-series of silicon elemental maps, while the phase-separated morphologies of polyisoprene rubber (IR) and styrene-butadiene rubber (SBR) are visualized by STEM-tomography in high-angle-annular-dark field (HAADF) mode. The combination of STEM-EDX and STEM-HAADF tomography enables us to determine the distribution of silica between the two rubber phases quantitatively even with high contents of silica up to 70 phr (weight parts per hundred rubber). It is found that silica is preferentially distributed in the SBR phase, but it is also distributed in the IR phase when the IR fraction in the total rubber components is higher than 40 wt%. The preferential distribution of silica in the SBR phase improves the dispersion of the IR domains. This is the first use of this technique for a multicomponent polymer system, showing the advantage to characterize the complicated multicomponent polymer composite morphologies.     

Preparation and properties of TiC-Ni cermets using Ni-plated TiC

TiC powders were coated with Ni by a chemical plating technique and the pressed compacts sintered at 1623K. The density of the sintered bodies was 98–99%. Compared with mechanically-mixed powder, Ni-plated TiC powders gave a more uniform microstructure in which TiC particles were well dispersed in the Ni matrix. The cermets exhibited ductile fracture for TiC-70 vol.% Ni and brittle fracture for TiC-30 vol.% Ni. The flexural strength was improved by the homogeneous dispersion of TiC. The thermal expansion coefficient increased with a decrease in Ni content, following a nearly linear law of mixtures on the basis of volume fractions of pure TiC and Ni.