Prediction of mean square radius of gyration of tree-like polymers by a general kinetic approach

This paper describes a kinetic method to predict the z-average molecular mean square radius of gyration of tree-like polymers formed by irreversible reactions, assuming Gaussian chains. It is based on the population balance equations for the two-sided molecular distributions of pendant chains associated with every chemically distinguishable kind of bonds. An automated method for the solution of those equations is valid both before as well as after gelation for complex kinetic schemes. Examples of its use are presented with polycondensation systems leading to hyperbranched polymers, the anionic polymerization of mono- and divinyl monomers and a radical polymerization with terminal branching and transfer to polymer.     

The CH4/NO/O2 “Lean-deNOx” Reaction on Mesoporous Mn-Based Mixed Oxides

High surface area Mn-based porous oxides (MANPO) containing additives like Ce, Sr and La were found to be very active and selective materials under 0.67% CH₄/0.2% NO/5% O₂ lean-deNO _x conditions in the 200–300°C low-temperature range. These materials perform also impressively in the presence of 4% H₂O in the feed stream, where a N₂ selectivity of 98% and an excellent stability over 24 h on stream have been observed. The MANPO materials can be considered serious competitors of noble metals for low-temperature lean-deNO _x applications.     

Study of the thermomechanical and electrical properties of conducting composites containing natural rubber and carbon black

This work describes the preparation and characterization of composite materials obtained by the combination of natural rubber (NR) and carbon black (CB) in different percentages, aiming to improve their mechanical properties, processability, and electrical conductivity, aiming future applications as transducer in pressure sensors. The composites NR/CB were characterized through optical microscopy (OM), DC conductivity, thermal analysis using differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMA), thermogravimetry (TGA), and stress–strain test. The electrical conductivity varied between 10^?9 and 10 S m^?1, depending on the percentage of CB in the composite. Furthermore, a linear (and reversible) dependence of the conductivity on the applied pressure between 0 and 1.6 MPa was observed for the sample with containing 80 wt % of NR and 20% of CB. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

The cationic polymerization of α-methylstyrene in liquid sulfur dioxide initiated by the HI/I2 system

The polymerization of α-methylstyrene (αMeSty) initiated by HI/I₂ or HI in the presence of liquid sulfur dioxide has been investigated. The number-average molecular weight increased with the monomer concentration for reactions initiated by the HI/I₂ system. I₂ also participates in the initiation process, increasing the number-average polymer chain at higher monomer concentration. HI alone is also able to initiate the polymerization of αMeSty in the presence of SO₂. With this initiator, transfer reaction can be minimized in systems containing low amount of SO₂. Received: 19 December 1996/Revised: 27 January 1997/Accepted 29 January 1997     

Controlling the phase stability of polymer blends through the introduction of impenetrable interfaces

In this work, the effect of the introduction of modified solid surfaces into polymer blends on the phase‐separation process was investigated. Glass fibers with surfaces having different chemistries were introduced into polystyrene–poly(methyl methacrylate) blends. The glass fibers used either had fully hydrated surfaces or had surfaces covered with a random copolymer, poly(styrene‐co‐methyl methacrylate). The copolymer was synthesized by free‐radical polymerization of styrene and methyl methacrylate in the presence of previously vinyl silane‐treated glass fibers. The copolymerization and grafting procedures were investigated by FTIR and thermal analysis. Blends containing the fibers were studied using FTIR microscopy and optical microscopy. FTIR microscopy results showed that the composition of the phases in the blends was shifted by using fibers with different surface chemistries. Fibers with grafted copolymers were capable of narrowing the immiscibility region in the phase diagram, while fully hydrated fibers were able to expand the gap. It was proposed that interfacial interactions regulated by a hydrophilic–hydrophobic type of forces were responsible for guiding the described phase‐separation process. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1619–1627, 2003     

Methanol Selective Oxidation to Formaldehyde over Iron-Molybdate Catalysts

This review deals with the important industrial reaction of formaldehyde manufacture by methanol oxidation over iron molybdate catalysts. Detailed reference is made to the used catalyst, preparation techniques (coprecipitation, sol-gel like, mechanical mixing, etc.) including unsupported and supported catalysts, promoters and characterization methods. The controversial active phase assignment (stoichiometric versus Mo rich iron molybdate) is discussed. The proposed reaction mechanisms and kinetic laws for the main and side reactions are examined. The catalyst deactivation processes are reviewed and the role of Mo excess on these processes is underlined. Finally conclusions and perspectives are presented.     

A web-based platform for biosignal visualization and annotation

With the advent of wearable sensing and mobile technologies, biosignals have seen an increasingly growing number of application areas, leading to the collection of large volumes of data. One of the difficulties in dealing with these data sets, and in the development of automated machine learning systems which use them as input, is the lack of reliable ground truth information. In this paper we present a new web-based platform for visualization, retrieval and annotation of biosignals by non-technical users, aimed at improving the process of ground truth collection for biomedical applications. Moreover, a novel extendable and scalable data representation model and persistency framework is presented. The results of the experimental evaluation with possible users has further confirmed the potential of the presented framework.     

Catkin liked nano-Co3O4 catalyst built-in organic microreactor by PEMOCVD method for trace CO oxidation at room temperature

In this paper, tricobalt tetraoxide (Co₃O₄) catalyst was coated on the polydimethylsiloxane microchannel by the plasma-enhanced metal-organic chemical vapor deposition technology. The obtained Co₃O₄ film was characterized by SEM, XRD, XPS, and TEM, and the results show that the as-deposited Co₃O₄ film was initially composed of many cauliflowers-shaped microclusters. Also, the microcauliflower was transformed from an amorphous phase to a crystal phase when the Co₃O₄ film was treated by Ar and O₂ plasma for more than 20 min, and the crystal lattice line occurred on the surface of nano-sized-Co₃O₄ particles. Meanwhile, the interface of Co₃O₄ particles with diameter between 3 and 12 nm became obvious and some nano-catkin structures were also formed on the Co₃O₄ film. The ratio of Co³⁺/Co²⁺ in the spinel-type Co₃O₄ was nearly 2, and the nano-particles predominantly expose their {311}, {111}, and {220} planes. These morphologies and structure characteristics were found to be ideal for increasing the catalytic activity efficiency of Co₃O₄ for CO oxidation, and the catalytic stability of Co₃O₄ coated on the organic microreactor lasted nearly 85 h for trace CO oxidation at room temperature.     

Activation of Pozzolanic Reaction of Hydrated Portland Cement Fly Ash Pastes in Sulfate Solution

The activation of the pozzolanic reaction of fly ash in portland cement paste immersed in sulfate solution has been studied. Mixtures of two Spanish fly ashes (ASTM class F) with 0%, 15%, and 35% replacement of portland cement by fly ash were immersed in Na₂SO₄ solution, of 2880 ppm SO₄²⁻ concentration, for a period of 90 days. The resistance of the different mixtures to the sulfate attack was evaluated using the Koch-Steinegger test. The results showed that all of the mixtures were sulfate resistant, despite the high Al₂O₃ content of the fly ash. The diffusion of SO₄²⁻ and Na⁺ ions through the pore solution activated the pozzolanic reactivity of the fly ashes, causing microstructural changes, which were characterized by X-ray diffraction (XRD), mercury intrusion porosimetry (MIP), and scanning electron microscopy (SEM). As a result, the flexural strength of the mixtures increased, principally for the fly ash of a lower particle size and 35% of addition.