Interactions in compatible polymer systems

Summary Dynamic mechanical measurements on polystyrene — poly(vinylmethylether) blends are demonstrating that the relaxation processes in the blends are mainly connected with the motions of the poly(vinylmethylether) chain.Concerning the effect of mixing on topological properties of the blends, an increase of the polydispersity of the relaxation processes is detected in blends with high molecular weight polystyrene while low molecular weight polystyrene exerts an effect of dilution upon the relaxation of the high molecular poly(vinylmethylether) chains.From these measurements as well as from thermoanalytical data it results that the energetic interaction is more pronounced in the blends with oligomeric than with high molecular weight polystyrene. The glass transition temperature shows a larger deviation from additivity for blends with high molecular polystyrene than for those with oligomeric polystyrene.Herrn Prof. Dr. M. Kryszewski zum 60. Geburtstag herzlichst gewidmet     

Processing and morphology of molecularly imprinted nylon thin films

The characterization of thin, selectively imprinted films of nylon‐6 was performed. Amino acids were used as template molecules. Spin‐cast films were prepared with sizes ranging from 2 μm to 300 nm, depending on the nylon and template concentration in the casting solution. The morphological characteristics of the film surface were examined by atomic force microscopy, and the structure within the films was observed by freeze‐fracture scanning electron microscopy. The film activity was clearly coordinated with the appearance of nanometer‐sized pores both on the surface and within the film. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2919–2926, 2006     

Reported food intake and distribution of body fat: a repeated cross-sectional study

Background  

Body mass, as well as distribution of body fat, are predictors of both diabetes and cardiovascular disease. In Northern Sweden, despite a marked increase in average body mass, prevalence of diabetes was stagnant and myocardial infarctions decreased. A more favourable distribution of body fat is a possible contributing factor.     

Foaming of nonionic surfactant solutions: Effect of surfactant concentration and temperature

Foaming of solutions of the nonionic surfactant, octoxynol 9, was investigated in the concentration range of 0.010 to 5.00% and in the temperature range of 7–37 C, well below the cloud point of 65 C, by measuring the height and stability of foams generated by pouring thin streams of surfactant solutions into a glass column. All foams were fast-thinning. Their height increased monotonically with surfactant concentration. The rate of change of foam height with log surfactant concentration underwent no change at the CMC of 0.018%, but was four times lower above 0.146% than below 0.146%. Foams at lower temperatures generally thinned somewhat more slowly and were stronger or more cohesive and more stable than foams generated at higher temperatures by surfactant solutions of comparable concentrations. Oxidative degradation reduced foam height somewhat. Octoxynol 9 and sodium lauryl sulfate, rated as a good foamer, produced foams of comparable volume and stability.     

Effect of electrolytes on foaming of nonionic surfactant solutions

The effect of electrolytes and other additives on the foaming of solutions of the nonionic surfactant octoxynol 9 (Triton X-100) was investigated and correlated with their effect on the cloud point. Foams were generated by pouring solutions as a thin stream into a vertical tube. The height of the generally fast-draining foam columns was measured as a function of time, and their stability was rated according to the damage sustained within 13 min. The surfactant concentrations used, 0.050, 0.100 and 2.00%, were above the critical micelle concentration. Increasing concentrations increased foam height but not foam stability. The electrolytes NaCl and Na₂SO₄ salted the surfactant out. They reduced its cloud point in proportion to their concentration. They also reduced the foam height, albeit to a lesser extent than the cloud point, but hardly reduced the foam stability below the cloud point.     

Leckageraten von Dichtungen für Flanschverbindungen: Einflußgrößen,Anforderungen, meßtechnische Erfassung und leckageratenbezogene Dichtungskennwerte

Flow theories can help in determining the fundamental interrelationships between the leak rate of gaskets for flange connections and the relevant influencing parameters. The basic rule for the transfer of results obtained for special boundary conditions to other conditions can be derived. In this way the effort involved in gasket testing can be reduced. This paper gives the interrelations between the leak rate of gaskets on the one hand and the internal pressure, the temperature, the medium, and the gasket thickness on the other and discusses them with aid of measured results. The effect of the gasket stress and thickness can be determined only of experimental investigations. Furthermore, the requirements placed on gaskets, the leak rate related gasket characteristics defined in various standards and the measuring techniques for their determination are discussed.     

A NUMERICAL SOLUTION OF THE FLOW AROUND A SPHERE IN A CIRCULAR CYLINDER

A numerical solution of the Navier-Stokes equations is presented for Poiseuille flow around an axially placed, fixed sphere in a circular cylinder. Streamlines and isovorticity lines are calculated from the governing equations for the strearnfunction and the vorticity. Isobars are calculated from a Poisson equation, derived from the Navier-Stokes equations. The pressure and vorticity distribution on the surface of the sphere, the additional pressure drop and the drag coefficients are presented. Solutions are obtained for Reynolds numbers up to 150 (based on cylinder diameter and mean velocity). The wall effects are examined by comparison with results of previous investigations for an unbounded flow around a sphere.     

Esterification and Transesterification of Renewable Chemicals

An overview is given of newly developed Lewis or Brønsted acid and base catalysts for esterification, transesterification and ester interchange reactions. The most relevant applications of these catalysts and reactions in the domain of renewable resources, in particular, oils and fats, are discussed.     

Restricted chain segment mobility in poly(amide) 6/clay nanocomposites evidenced by quasi-isothermal crystallization

Modulated temperature differential scanning calorimetry is used to explore the interactions between a poly(amide) 6 matrix and various types of clay reinforcement. During quasi-isothermal crystallization of the polymer/clay nanocomposites, an excess contribution is observed in the recorded heat capacity signal, due to reversible melting and crystallization. It is proposed that the magnitude of this excess contribution can be used to qualify the polymer/clay interfacial interaction, as it is directly linked to the segmental mobility of the polymer chains in the interphase region, where both the crystalline and amorphous polymer fractions are affected. It is shown that the interfacial interaction strongly depends on the type of clay filler used. These interactions play a key role in the development of specific material properties for the different types of nanocomposites. A simple interphase model for the poly(amide) 6/clay nanocomposites is proposed.