Thermodynamic compatibility of sepiolite-filled poly(vinylidene fluoride)-polystyrene blends

Summary Inverse gas chromatography (IGC) and differential scanning calorimetry (DSC) were used to investigate the effect produced by sepiolite on the thermodynamical compatibility of poly(vinylidene fluoride)-polystyrene blends. Polymer-polymer interaction parameters were calculated from the retention data, for various polar and non-polar probes in pure and mixed stationary phases of these polymers, using sepiolite as solid support, as well as from melting point depression analysis of the sepiolite filled blends. Both techniques give us positive values of the interaction parameters, in accordance with the non-compatibility of these blends; However negative values of the interaction parameters were obtained for polystyrene-rich blends (_PS 85 wt%) and high sepiolite loadings, indicating that sepiolite acts as a compatibilizing agent for the system PVF₂/PS.     

Changes of volatile compounds in wine vinegars during their elaboration in barrels made from different woods

Changes in the volatile components of red wine vinegars and balsamic vinegars were investigated during 1 year of aging in wood barrels and bottles. Barrels of four different woods (oak, chestnut, acacia and cherry) were used. A total of 57 volatile compounds were analysed by Gas Chromatography–Flame Ionization Detection (GC–FID) and Headspace Sorptive Extraction GC–Mass Spectrometry (HSSE-TD–GC–MS). We observed significant increases in the total content of volatile compounds only for balsamic vinegars. The concentrations of ethyl furoate, ethyl benzoate, benzaldehyde and acetophenone were highest in cherry barrels. These compounds, then, seem to be characteristic of this wood. Oak lactones presented the highest increases for vinegars aged in oak. Eugenol was only present in vinegars aged in chestnut and oak barrels. Oak and cherry seem to be the best type of wood for aging of vinegar due to their distinctive aromatic characteristics.     

Phenomenon of phase inversion in high impact polystyrene: Physico‐chemical,rheological and morphological study in the presence of chain transfer agent and using different tapered block copolymers as the precursor rubber

Different high impact polystyrenes were synthesized using styrene/butadiene copolymers (SB) with PS/PB composition: 30/70 and 20/80 as the precursor rubber, benzoyl peroxide (BPO) as the initiator, and ter‐dodecyl mercaptane (TDM) as the chain transfer agent. During the polymerization, several samples were taken and analyzed under different techniques to evaluate the phase inversion (PI) phenomenon. The PI was determined through transmission electron microscopy (TEM) and through dynamic oscillatory behavior, where the PI takes places when the relaxation process presents the lower value of activation energy. Finally, the Choi and Schowalter emulsion model was employed to elucidate the PI, and relevant information was revealed about the interfacial tension in the PI. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Improved toughness in HIPS obtained from different styrene/butadiene‐graded block copolymers through modification of the polydispersity index of the PS block

The polymerization of styrene in the presence of graded block copolymers with a polystyrene/polybutadiene composition of 40/60, 30/70, and 20/80 and with a polydispersity index (M_w /M_n ) in the polystyrene block varying from 1.1 to 1.6 was studied. As the polydispersity index of the polystyrene block increases, an improvement of up to 50% in the Izod impact toughness of the produced high‐impact polystyrene was achieved. The rubber particle morphology type, the size, and the volume fraction of the rubber phase particles could be modified through changes in the composition of the graded block copolymer. The changes that occurred in the rubber phase were mainly generated by the variation in the interfacial tension between the phases, and this variation was principally attributed to an increase in the polydispersity index of the polystyrene block in the precursor copolymer. POLYM. ENG. SCI., 46:1333–1341, 2006. © 2006 Society of Plastics Engineers     

Optimization of Combined Microwave–Hot Air Roasting of Malt Based on Energy Consumption and Neo-Formed Contaminants Content

ABSTRACT: To produce specialty malt, malts were roasted by combined microwave–hot air at various specific microwave powers (SP = 2.5 to 3 W/g), microwave heating times (t_mw = 3.3 to 3.5 min), oven temperatures (T_oven = 180 to 220 °C), and oven heating times (t_oven = 60 to 150 min). The response variables, color, energy consumption by microwave (E_mw) and oven (E_oven), total energy consumption (E_tot), quantity of neo-formed contaminants (NFCs), which include hydroxymethylfurfural, furfural, furan, and acrylamide were determined. Response surface methodology (RSM) was performed to analyze and predict the optimum conditions for the specialty malt. Production using combined microwave–hot air roasting process based on minimum energy consumption and level of NFCs. At 95% confident level, SP, T_oven, and t_oven were the most influencing effects with regard to E_tot, whereas t_mw did not affect E_tot. T_oven and t_oven significantly affected malt color. Only T_oven significantly influenced the NFCs content. The optimum parameters were: SP = 2.68 W/g for 3.44 min, T_oven = 206 °C for 136 min for coffee malt, SP = 2.5 W/g for 3.48 min, T_oven = 214 °C for 136 min for chocolate malt, and SP = 2.5 W/g for 3.48 min, T_oven = 211 °C for 150 min for black malt. Comparing with conventional process, combined microwave–hot air reduced E_tot by approximately 40%, 26%, and 26% for coffee, chocolate, and black malts, respectively, and reduced HMF, furfural, furan, and acrylamide contents by 40%, 18%, 23%, and 95%, respectively, for black malt. Practical Application: An important goal for research institutions and the brewery industry is to produce colored malt by combining microwave and hot air roasting, while saving energy, getting desirable color, and avoiding the formation of carcinogenic and toxic neo-formed contaminants (NFCs). Therefore, one objective of this study was to compare energy consumption and content of NFCs during roasting of malt by hot air-only and combined microwave–hot air processes as well as to determine the effect of specific power, microwave processing time, oven temperature, and oven processing time during combined microwave–hot air roasting. Another objective was to predict the optimum conditions for the production of coffee, chocolate, and black malts.     

Fluid Dynamics of Vortex Formation in Tundish Operations: Mathematical Modelling

A mathematical model was developed to study the significance of the fluid dynamics of vortex formation in tundish operations. The aim is to contribute to the fundamental understanding of vortex formation and related phenomena. For this purpose a typical slab tundish was employed; the mathematical model was solved using FLUENT® commercial software capable to simulate highly turbulent flows. The well known k‐? turbulence model was applied to compute this effect in the process. The mathematical simulations confirmed the results from a water analogue model. The vortex formation is directly related to the highly turbulent flows present in the reactor. Great changes in velocity fields during short times and large distances between the upper edge of the dam and the free surface of the bath enhance the formation of vortex flows.     

Factors controlling flavors binding constants to cyclodextrins and their applications in foods

The binding constants of 14 different flavors (Maltol, Furaneol, Vanillin, Methyl Cinnamate, Cineole, Citral, Menthol, Geraniol, Camphor, Nootkatone, Eugenol, p-vinil Guayacol and Limonene) to cyclodextrins (α-cyclodextrin and β-cyclodextrin) have been determined by an UV–Vis spectrophotometric technique. In all cases the binding constant of flavors to β-cyclodextrin are bigger than the corresponding one to α-cyclodextrin. This fact is due to the different size of cyclodextrin cavity. As well as, a relationship between log P of each flavor and the binding constants was found, proving that the driving force for host–guest complex formation is hydrophobic/hydrophilic interactions.     

Performance tradeoffs among low‐complexity detection algorithms for MIMO‐LTE receivers

The upcoming Third‐Generation Partnership Project—Long‐Term Evolution (3GPP‐LTE) cellular standard will employ spatial multiplexing to significantly increase the data rates. Detection of the spatially multiplexed signals is an essential issue in the design of an LTE receiver. In this paper, we evaluate the performance–complexity tradeoffs for a set of low‐complexity multiple input multiple output (MIMO) detection algorithms in a realistic LTE downlink system. Specifically, antenna correlation and channel estimation errors have been considered for a practical MIMO‐LTE receiver. An LTE downlink model has been implemented in order to evaluate three types of detectors: linear, unsorted successive interference cancellation (SIC), and ordered SIC. Our simulation results show that the unsorted SIC detectors present a very poor performance–complexity tradeoff. Besides, linear detectors are shown to be the best candidates as the performance improvement for the ordered SIC detectors is not significant in a realistic scenario. Copyright © 2009 John Wiley & Sons, Ltd.