Vapor‐induced swelling of supported methacrylic and siloxane polymer films: Determination of interaction parameters

White light reflectance spectroscopy is applied to monitor vapor‐induced thickness changes of polymer films, supported on suitable silicon substrates. Assuming unidirectional swelling due to the constraining support, the equilibrium volume swelling of four methacrylic polymers and two siloxane‐based copolymers upon exposure to various activities of water, methanol, ethanol, and ethyl acetate vapor, at 30°C is evaluated. The deduced sorption isotherms were fitted to the Flory‐Huggins equation and interaction parameters, as well as solubility coefficients at infinite solute dilution, were deduced for each binary system. The relative sorption capacity of the different classes of polymers toward the four vapors are in line with the expected solubility interactions between solvent and solute. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Prediction of the n‐hexane/water and 1‐octanol/water partition coefficients for environmentally relevant compounds using molecular simulation

In recent years molecular simulation has emerged as a useful tool to predict physical properties of complex chemical systems. A methodology to estimate the n‐hexane/water and 1‐octanol/water partition coefficients of environmentally relevant solutes, namely substituted alkyl‐aromatic molecules, chlorobenzenes, polychlorinated biphenyls (PCBs) and polychlorinated diphenyl ethers (PCDEs) using molecular simulation is elucidated here. The partition coefficients are calculated based on the absolute solvation Gibbs energies in each phase which are estimated from molecular dynamics simulations employing the thermodynamic integration approach. Very encouraging results, with average absolute deviations of 0.4 log P units are presented. Consequently, this molecular‐based approach with a strong physical background can provide reliable prediction of the partition coefficients in different solvent pairs without the a priori knowledge of experimental data. © 2011 American Institute of Chemical Engineers AIChE J, 58: 1929–1938, 2012     

Foaming of polymers with supercritical CO2: An experimental and theoretical study

Microcellular polystyrene (PS) foams and porous structures of the biodegradable poly(d,l-lactic acid) (P_d,lLA) were prepared with the batch foaming technique (pressure quench) using supercritical CO₂ as blowing agent. The effect of pressure, temperature and depressurization rate on the final porous structure was investigated. The results revealed that the size of the pores decreases and their population density increases with pressure increase, or decrease of temperature, and/or increase of the depressurization rate. The results were correlated by combining nucleation theory with NRHB model in order to account for and emphasize the physical mechanism related to nucleation of bubbles inside the supersaturated polymer matrix. A satisfactory agreement between correlations and experimental data was obtained indicating that the nucleation theory yields quantitative correlations when variables such as sorption, degree of plasticization, and surface tension of the system polymer-supercritical fluid are accurately described.     

Antioxidant activity of red wine phenolic extracts towards oxidation of corn oil

The antioxidant activity of Xinomavro red wine phenolic extracts in corn oil stripped of tocopherols was evaluated. One wine extract, at 100 mg/L total phenolics, rich in phenolic acids and flavonols, inhibited the oxidation of corn oil stripped of tocopherols to a greater extent than butylated hydroxyanisole, at 200 mg/L. Moreover, another extract, at 100 mg/L total phenolics, rich in flavanols, flavonols and tyrosol, also exhibited high inhibitory action. The present results indicate that some red wine phenolics – such as phenolic acids, flavonols or flavanols – may be strong antioxidants in corn oil.     

Simulation and modelling methods in aluminium rolling industry

Aluminium coil production plants can be described as multi-stage processes which are often characterised by complexity and are expected to manipulate huge amount of data. Effective scheduling is a key issue for these processes since it can improve throughput rates and machine utilisation. This paper studies the production line of companies which produce high-quality rolled aluminium lithographic strips. An efficient representation for such production processes is provided and subsequently used for an extensive analysis and performance evaluation through appropriate metrics. In particular, the work addresses the implementation of an overall model in a simulation environment, capable of integrating the various aspects of the specific production management processes. The model was successfully validated using actual production data, and it was found that it is suitable for the modelling, analysis and performance evaluation of the complex aluminium coils production process. With the aid of the model, various scenarios were investigated via extensive simulation runs, such as installing additional machine centres and reducing pre-set times the products spend in intermediate storage areas.     

Large Power Increase Enabled by High-Q Diamond-Loaded Cavities for Terahertz Gyrotrons

Journal of Infrared, Millimeter, and Terahertz Waves - A new operation scheme is proposed to enable large increase in output power of terahertz gyrotrons. In this scheme, the gyrotron operates in...     

Temporal trends of polybrominated diphenyl ethers and hexabromocyclododecane in milk from Stockholm mothers, 1980-2004

Environmental and human exposures to brominated flame retardants (BFR) have been of emerging concern since some BFR are persistent and bioaccumulative compounds. Among those, polybrominated diphenyl ethers (PBDE) have frequently been reported in low to high ng/g concentrations in human blood around the world while hexabromocyclododecane (HBCDD) only occasionally has been reported and then in the low ppb concentrations in human blood. The present study concerns PBDE congener and HBCDD concentrations in human milk from Stockholm from 1980 to 2004. HBCDD concentrations has increased four to five times since 1980 until 2002 but seems to have stabilized at this concentration in the last years (2003/04). Similarly, BDE-153 has continued to increase at least to 2001, after which it has stabilized in the mother's milk. Other PBDE congeners with four to five bromine substituents peaked 5 years earlier (1995) and are all decreasing. DecaBDE (BDE-209) is not a suitable biomarker for time trend studies according to the present results, showing no changes over time. This is likely due to its short apparent half-life in humans and poor transfer from blood to milk.