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     

Lightweight dynamic symmetry breaking

Symmetries in constraint problems present an opportunity for reducing search. This paper presents Lightweight Dynamic Symmetry Breaking, an automatic symmetry breaking method that is efficient enough to be used as a default, since it never yields a major slowdown while often giving major performance improvements. This is achieved by automatically exploiting certain kinds of symmetry that are common, can be compactly represented, easily and efficiently processed, automatically detected, and lead to large reductions in search. Moreover, the method is easy to implement and integrate in any constraint system. Experimental results show the method is competitive with the best symmetry breaking methods without risking poor performance.     

Computational Aspects of Uncertainty Profiles and Angel-Daemon Games

We analyze the complexity of equilibria problems for a class of strategic zero-sum games, called angel-daemon games. Those games were introduced to asses the performance of the execution of a web orchestration on a moderate faulty or under stress environment. Angel-daemon games are a natural example of zero-sum games whose representation is naturally succinct. We show that the problems of deciding the existence of a pure Nash equilibrium or of a dominant strategy for a given player are ${\Sigma}^{p}_{2}$ -complete. Furthermore, computing the value of an angel-daemon game is EXP-complete. Thus, our results match the already known classification of the corresponding problems for the generic families of succinctly represented games with exponential number of actions.     

Processing peanuts and cottonseed

Two cases are presented to show how the elimination of bad operational habits and the use of controlling equipment can improve the efficiency of an oil mill. The cleaning of peanuts (farmer’s stock) is presented as an example of the need to use proper equipment for a given operation. A supply of good quality seed, together with the use of modern equipment, has improved the yields of oil and protein to the present values of 91% and 96% recovery, respectively. A growing fats and oils market in the Central American area and a limited supply of cottonseed are forcing the mills of Nicaragua to look for new oilseeds.     

A quantitative feedback solution to the multivariable tracking error problem

This paper introduces a novel solution for the multi‐input multi‐output (MIMO) quantitative feedback theory control design problem with tracking error specifications. Looking for a minimum controller overdesign, the technique finds new controller quantitative feedback theory bounds based on necessary and sufficient conditions for the existence of suitable associated prefilter matrix elements. It improves previous approaches to the subject and includes (i) the possibility of a free selection of the nominal plant, (ii) a less conservative application of the Schwartz inequality to decisively reduce the potential controller overdesign, (iii) a methodology to design independently the elements of the prefilter matrix, and (iv) a scope of application to both sequential and nonsequential MIMO controller design methods. The benefits of the new control design technique are illustrated by means of two examples. The first one, a standard 2 × 2 MIMO problem, is provided for comparison purposes with previous approaches. The second example, included as a major control challenge, deals with a well‐known demanding distillation column benchmark problem. Copyright © 2013 John Wiley & Sons, Ltd.     

Relation of swelling and Tg depression to the apparent free volume of a particle‐filled,epoxy‐based adhesive

The effect of hygrothermal aging on a particle‐filled, epoxy‐based adhesive was studied using a gravimetric sorption technique. This study has explored moisture sorption characteristics as well as the associated behaviors of swelling and the depression of the glass transition temperature (T_g). We observed that the diffusion of water in this adhesive has a non‐Fickian behavior, and the depression of T_g proceeds to a definite value that is independent of the final equilibrium water content of the system. Our observations suggest that water diffuses into the polymer in a dual‐sorption mode, in which water resides in two populations. In one population, water is considered to occupy apparent free volume of the adhesive, and the second population water infiltrates polymer structure and forms hydrogen‐bonded clusters. Our results show that hygrothermal aging temperature and swelling do not alter the apparent free volume of this adhesive. We conclude that the constant value of T_g depression at saturation implies that only water in the apparent free volume is responsible for the T_g depression, whereas the swelling proceeds through the formation of hydrogen bonds in the adhesive. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1436–1444, 2003     

A novel attractant for Mexican fruit fly,Anastrepha ludens,from fermented host fruit

Chemicals from fermented chapote fruit were identified and evaluated as attractants for hungry adult Mexican fruit flies in laboratory and greenhouse bioassays. Twenty-eight chemicals identified from an attractive gas-chromatography fraction were as attractive as a chapote volatiles extract (CV) when mixed in the same amounts found in CV. Sixteen of the chemicals were slightly attractive to flies when tested individually. A mixture containing 15 of the chemicals by design and the 16th as an impurity, in arbitrary concentrations, was at least as attractive as the original CV. In a series of experiments, the number of chemicals was reduced to three by elimination of unnecessary components. The three-component mixture retained the attractiveness of the 15-component mixture. The three chemicals were 1,8-cineole, ethyl hexanoate, and hexanol (CEH). Attractiveness of the three-chemical mixture was equal to the sum of the attractiveness of the three individual components, suggesting that each chemical binds to a different receptor type that independently elicits partial attraction behavior. Optimal ratios were 1011 of the three chemicals, respectively. Optimal test quantities ranged between 0.4–4g of 1,8-cineole and 40–400 ng each of ethyl hexanoate and hexanol applied to filter paper in the laboratory bioassays. A neat 1011 mixture of the chemicals was 1.8 times more attractive than aqueous solutions ofTorula dried yeast and borax to starved 2-day-old flies when the lures were tested in competing McPhail traps in a large greenhouse cage.Diptera: Tephritidae.     

Addition compatibilization of PP/PS blends by tailor‐made copolymers

The thermoplastic polymer blends of commercial interest generally need a phase compatibilization to reduce the interfacial tension, to stabilize the morphology, and to increment the interfacial adhesion. This work deals with the compatibilization of PP/PS blends by addition of a tailor‐made copolymer, which is prepared from the pure homopolymers by a Friedel‐Crafts reaction. This addition compatibilization process comes out as an economic alternative applicable to the recycling of mixed plastics from urban and industrial wastes. The influence of compatibilizer concentration and blending time on the emulsifying effect, morphology, and mechanical properties of the resulting blends are analyzed. The compatibilization process effectiveness is assessed through the improvement in phase adhesion, emulsification and ductility of the compatibilized with respect to the physical blends. An increase of three times in ductility is achieved using very low compatibilizer concentrations (0.5–0.7 wt%). No appreciable detriment in yield strength or modulus is observed in these compatibilized blends. POLYM. ENG. SCI. 46:329–336, 2006. © 2006 Society of Plastics Engineers     

Pd catalysts supported on silicon nitride for the combustion of methane: Influence of the crystalline and amorphous phases of the support and of the preparation method on the catalytic performances

Non-oxide refractory materials, such as silicon nitride having high thermal stability and thermal conductivity can be used as catalytic supports. The influence of the Si₃N₄ support nature and of the chemical compounds used for preparations on the physical-chemistry and catalytic properties of the palladium systems in the total oxidation of methane was investigated. A strong influence of the phase composition and the crystalline state of supports on the catalytic properties in the total oxidation of methane of the Pd catalysts was found. The activity of Pd catalysts increases with the -Si₃N₄ content and crystallization state of the support. The catalytic activity of Pd/-Si₃N₄ is also strongly affected by the preparation procedure. The Pd/-Si₃N₄ catalyst obtained by aqueous impregnation is less active and less stable. It was proposed that if water is used as an impregnation solvent, the surface acid-based properties of Si₃N₄ support and/or of the Pd active phase are irreversibly damaged. Pd supported on -Si₃N₄, prepared by impregnation of the Pd precursors in toluene solutions are found to be the most active and stable under reaction conditions.     

Carbon nanotube supported ruthenium catalysts for the treatment of high strength wastewater with aniline using wet air oxidation

Multi-walled carbon nanotubes (MWCNT) can be efficiently used as support of ruthenium catalysts for the catalytic wet air oxidation of high strength wastewater containing aniline. Catalysts were prepared using different ruthenium precursors, Ruthenocene [Ru(η⁵-C₅H₅)₂], Ruthenium (1,5-cyclooctadiene, 1,3,5-cyclooctatriene) [Ru(cod)(cot)] and Ruthenium trichloride (RuCl₃ · xH₂O), different impregnation methods (excess solution and incipient wetness impregnation) and different MWCNT support surface chemistry (nitric acid oxidized MWCNT-COOH and Na₂CO₃ ion exchanged MWCNT-COONa). The efficiency of the aniline removal obtained with the catalysts prepared with different precursors decreases in the order [Ru(cod)(cot)] > RuCl₃ · xH₂O > [Ru(η⁵-C₅H₅)₂], 100% aniline conversion being obtained after 45 min of reaction with the catalyst prepared with [Ru(cod)(cot)]. The influence of the impregnation technique was found to be negligible, while the use of the MWCNT-COONa support led to increased catalyst performances when compared to that obtained with catalysts prepared with the MWCNT-COOH support. Leaching of ruthenium was observed in all cases, but the use of the precursor [Ru(cod)(cot)] and of the support MWCNT-COONa in the preparation of the catalysts seems to improve their stability. A direct relationship between metal load and catalyst stability was found and attributed to the strength of metal-support interactions.