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In supercritical carbon dioxide (C[O.sub.2]) assisted polymer processes the solubility of C[O.sub.2] in a polymer plays a vital role. The higher the amount of C[O.sub.2] dissolved in a polymer the higher is the viscosity reduction of the polymer. Solubilities of C[O.sub.2] in polyester resins based on propoxylated bisphenol (PPB) and ethoxylated bisphenol (PEB) have been measured using a magnetic suspension balance at temperatures ranging from 333 to 420 K and pressures up to 30 MPa. An optical cell has been used to independently determine the swelling of the polymers, which has been incorporated in the buoyancy correction. In both polyester resins, the solubility of C[O.sub.2] increases with increasing pressure and decreasing temperature as a result of variations in C[O.sub.2] density. The experimental solubility has been correlated to the Sanchez-Lacombe equation of state. POLYM. ENG. SCI., 46:643-649, 2006. © 2006 Society of Plastics Engineers, INTRODUCTION Polyester resins in powder form are frequently used in paint and toner industry. Milling, grinding, and spray drying are the particle formation processes commonly used in the industry. Narrow [...]

The oxidation of potassium iodide, bubble cloud visualization studies and sound attenuation measurements are applied to determine the influence of hydrostatic pressure on chemical reactions induced by 20 kHz ultrasound. It is demonstrated that a rise in hydrostatic pressure leads in a rise in yield for the oxidation of potassium iodide in aqueous solution and the sound field is more intense for higher pressures.

The use of multifunctional amphiphiles that bind multivalent cations in a reversible way by introducing acid groups that provide sufficient charge density to bind multivalent ions only above the critical micellization temperature (CMT) is demonstrated. The proposed surfactant modification provides a generic approach to obtain carboxylic acid end-standing (CAE) surfactants.

A stator-rotor-stator spinning disc reactor is presented, which aims at intensification of convective heat-transfer rates for chemical conversion processes. Single phase fluid-rotor heat-transfer coefficients hr are presented for rotor angular velocities [ABSTRACT FROM AUTHOR]

Abstract: It is well known that sonochemistry is less efficient at high acoustic intensities. Many authors have attributed this effect to decoupling losses and shielding of the acoustic wave. In this study we investigate both phenomena for a 20kHz ultrasound field with an intensity ranging from 40 to 150W/cm2. Visualization of the bubble cloud has demonstrated that the void fraction below the ultrasound horn increases more than proportional with increasing power input. Nevertheless, the energy coupling between the horn and the liquid remains constant; this implies that decoupling losses are not reinforced for larger bubble clouds. On the contrary, microphone measurements have shown that due to the larger bubble cloud a substantial part of the supplied energy is lost at high power inputs. In striving towards more efficient sonochemistry, reduction of shielding appears as one of the major challenges. [Copyright &y& Elsevier]

Temperature polarization effects can considerably limit the overall performance of pervaporation modules. This study shows the measurement of temperatures in a pervaporation membrane module using ultrasonic computer tomography (U-CT). With this technique complete 2D-temperature distributions that occur in the module can be measured within seconds. Temperature distributions were also determined using computational fluid dynamics (CFD). Both temperature distributions are comparable and show that in the tubular pervaporation system studied, temperature segregation occurs. This segregation is a result of the occurring hydrodynamics in the system that is determined by mixed convection. Also, the measured water fluxes through the membrane show to be dependent of forced and natural convection. [Copyright &y& Elsevier]

Abstract: The physics and chemistry of nonlinearly oscillating acoustic cavitation bubbles are strongly influenced by the dissolved gas in the surrounding liquid. Changing the gas alters among others the luminescence spectrum, and the radical production of the collapsing bubbles. An overview of experiments with various gas types and concentration described in literature is given and is compared to mechanisms that lead to the observed changes in luminescence spectra and radical production. The dissolved gas type changes the bubble adiabatic ratio, thermal conductivity, and the liquid surface tension, and consequently the hot spot temperature. The gas can also participate in chemical reactions, which can enhance radical production or luminescence of a cavitation bubble. With this knowledge, the gas content in cavitation can be tailored to obtain the desired output. [Copyright &y& Elsevier]

Abstract: The sonochemical oxidation efficiency of a commercial titanium alloy ultrasound horn has been measured using potassium iodide as a dosimeter at its main resonance frequency (20kHz) and two higher resonance frequencies (41 and 62kHz). Narrow power and frequency ranges have been chosen to minimise secondary effects such as changing bubble stability, and time available for radical diffusion from the bubble to the liquid. The oxidation efficiency, , is proportional to the frequency and to the power transmitted to the liquid (275mL) in the applied power range (1–6W) under argon. Luminol radical visualisation measurements show that the radical generation rate increases and a redistribution of radical producing zones is achieved at increasing frequency. Argon, helium, air, nitrogen, oxygen, and carbon dioxide have been used as saturation gases in potassium iodide oxidation experiments. The highest has been observed at 5W under air at 62kHz. The presence of carbon dioxide in air gives enhanced nucleation at 41 and 62kHz and has a strong influence on . This is supported by the luminol images, the measured dependence of on input power, and bubble images recorded under carbon dioxide. The results give insight into the interplay between saturation gas and frequency, nucleation, and their effect on . [Copyright &y& Elsevier]

Abstract: A new route for the chlorination of methane is described using ultrasound irradiation, which allows for an intrinsically safe process at ambient pressure and temperature. By tuning the gas feed composition methyl chloride yields of up to 19% have been obtained. [Copyright &y& Elsevier]