Development and evaluation of terminally epoxidized triglycerides for coatings applications

Epoxidized 10-undecenoic acid triglyceride, an experimental seed oil derivative that has a terminal epoxy group on each of the three acyl glyceride segments, has been found to have good reactivity with amine curatives and allows room temperature cures to be obtained. Coatings based on epoxidized 10-undercenoic acid triglyceride have also shown excellent UV stability. As an example, coatings samples placed in a QUVA chamber exhibit no loss in gloss after 3000 hr of a cycled exposure to high intensity UV lamps and moisture at temperatures of 50–60°C. In comparison, coatings based on standard liquid epoxy resins (LERs) and commercially available hydrogenated LERs lose gloss due to chalking/decomposition within 200–800 hr. Presented at the 81 st Annual Meeting of the Federation of Societies for Coatings Technology, November 12–14, 2003, in Philadelphia, PA.     

The importance of wet-powder dynamic mechanical properties in understanding granulation

Granule impact deformation has long been recognised as important in determining whether or not two colliding granules will coalesce. Work in the last 10 years has highlighted the fact that viscous effects are significant in granulation. The relative strengths of different formulations can vary with strain rate. Therefore, traditional strength measurements made at pseudo-static conditions give no indication, even qualitatively, of how materials will behave at high strain rates, and hence are actually misleading when used to model granule coalescence. This means that new standard methods need to be developed for determining the strain rates encountered by granules inside industrial equipment and also for measuring the mechanical properties of granules at these strain rates. The constitutive equations used in theoretical models of granule coalescence also need to be extended to include strain-rate dependent components.     

Morphology,crystallinity, and electrochemical properties of in situ formed poly(ethylene oxide)/TiO2 nanocomposite polymer electrolytes

A method to produce nanocomposite polymer electrolytes consisting of poly(ethylene oxide) (PEO) as the polymer matrix, lithium tetrafluoroborate (LiBF₄) as the lithium salt, and TiO₂ as the inert ceramic filler is described. The ceramic filler, TiO₂, was synthesized in situ by a sol–gel process. The morphology and crystallinity of the nanocomposite polymer electrolytes were examined by scanning electron microscopy and differential scanning calorimetry, respectively. The electrochemical properties of interest to battery applications, such as ionic conductivity, Li⁺ transference number, and stability window were investigated. The room‐temperature ionic conductivity of these polymer electrolytes was an order of magnitude higher than that of the TiO₂ free sample. A high Li⁺ transference number of 0.51 was recorded, and the nanocomposite electrolyte was found to be electrochemically stable up to 4.5 V versus Li⁺/Li. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2815–2822, 2003     

Self-assembled nano-phase particles for enhanced oxygen barrier coatings on polymeric materials

Aqueous-based inorganic–organic hybrid coating materials comprising self-assembled nanophase particles (SNAP) were investigated for their potential to confer high gas barrier performance to flexible polymeric substrates, particularly to improve suitability of the substrates as encapsulation materials for organic photovoltaic (OPV) devices. Potential benefits of this approach include versatility in barrier coating formulation to achieve specific barrier properties, and application of coatings in a reel-to-reel process under ambient conditions. The present study focused on enhancement of the oxygen barrier performance of polypropylene (PP) substrates by applying SNAP-based coatings with and without the addition of an oxygen scavenging additive. SNAP particles were characterised using ²⁹Si NMR and dynamic light scattering, and coatings were analysed using atomic force microscopy and X-ray photoelectron spectroscopy. SNAP particle preparation and coating formulation was optimised with respect to oxygen transmission rate (OTR) of the coating on PP, and mechanical properties of the coating solution. In the absence of oxygen scavenger, the lowest OTR attained for the SNAP-based coatings was 0.87 cm³ mil m⁻² day⁻¹ atm⁻¹. The OTR was further reduced to 0.22 cm³ mil m⁻² day⁻¹ atm⁻¹ on addition of 9,10-anthraquinone-2,6-dissulfonic acid (AQDS) into the coating as an oxygen scavenger. These results represent a decrease in OTR by 4 orders of magnitude compared with uncoated PP, and the oxygen barrier obtained by addition of AQDS surpasses the performance of many plastic materials considered to be high oxygen barriers in the food and pharmaceutical industries.     

Chemical Analysis with High Spatial Resolution by Rutherford Backscattering and Raman Confocal Spectroscopies: Surface Hierarchically Structured Glasses

Copper and iron in glasses constitute classical aims of study because of the optical effects that they produce. Structured materials are also interesting due to the incorporated functionalities derived from their spatial organization. Here, CuO and Fe₂O₃ were incorporated into a standard glass, from which glass coatings with different thicknesses were studied. Whereas iron cations dissolved in the glassy matrix, copper cations saturated it and crystallized at the surface, forming a hierarchical microstructure. The surface microstructure consisted of crystallizations of Tenorite (CuO) forming interconnected walls. The walls surrounding areas of glassy matrix gave rise to a cells microstructure. Rutherford Backscattering Spectrometry provided the composition of the samples with high depth resolution, and Raman Confocal Microscopy determined the phases location and their distribution forming the microstructure. The joint information from both techniques allowed high chemical and spatial resolution of the main cations location for the hierarchical surface microstructure.     

Multiobjective optimization of biorefineries with economic and safety objectives

A new approach for the incorporation of safety criteria into the selection, location, and sizing of a biorefinery is introduced. In addition to the techno‐economic factors, risk metrics are used in the decision‐making process by considering the cumulative risk associated with key stages of the life cycle of a biorefinery that includes biomass storage and transportation, process conversion into biofuels or bioproducts, and product storage. The fixed cost of the process along with the operating costs for transportation and processing as well as the value of the product are included. An optimization formulation is developed based on a superstructure that embeds potential supply chains of interest. The optimization program establishes the tradeoffs between cost and safety issues in the form of Pareto curves. A case study on bio‐hydrogen production is solved to illustrate the merits of the proposed approach. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2427–2434, 2013     

Electrical Properties of Stoichiometric BiFeO3 Prepared by Mechanosynthesis with Either Conventional or Spark Plasma Sintering

Phase‐pure powders of stoichiometric BiFeO₃ have been prepared by mechanosynthesis. Ceramics sintered by either conventional heating in air or spark plasma sintering (SPS) followed by oxidative anneal in air are highly insulating at room temperature with resistivity, extrapolated from the Arrhenius plots, of ~10¹⁶ Ωcm and activation energy 1.15(2) eV, comparable with those of a good‐quality BiFeO₃ single crystal. By contrast, the as‐prepared SPS sample without the postsinter anneal shows lower resistivity, e.g., ~10¹⁰ Ωcm at 25°C and activation energy 0.67(3) eV, indicating some reduction in the sample by the SPS process. The reason for the high conductivity reported for some ceramic samples in the literature remains unclear at present.     

Enhanced Hydrothermal Resistance of Y‐TZP Ceramics Through Colloidal Processing

Two commercial zirconia powders with 3 mol% of yttria (TZ3YE and TZ3YS, labeled as ZE and ZS, respectively) supplied by Tosoh (Japan) were used for this study. Maximum colloidal stability for ZE was achieved by dispersing the powders in a mixture of water/ethanol of 90:10 (wt/wt) using a sonication probe. The rheological behavior of the suspensions was optimized in terms of solids content ranging from 20 to 33 vol% and sonication time (0–6 min), the best results being obtained after 2 min. ZS samples were prepared to a solids loading of 30 vol% in water dispersing with 2 min‐sonication. Samples obtained by slip casting in plaster molds were used for dynamic sintering studies, and fully dense and nanostructured specimens were obtained at temperatures of 1300°C–1350°C (ZE samples) and 1400°C per 2 h (ZS samples). The Hardness (H) and Young's Modulus (E) properties of the specimens were studied by nanoindentation technique giving 17 and 250 GPa mean values for H and E, respectively. The specimens were then forced to a low‐temperature degradation (LTD) treatment at 130°C for 240 h in steps of 60 h. Raman spectroscopy and nanoindentation results of hydrothermally treated samples showed the absence of transformation from tetragonal to monoclinic phase until 180 h whereas the mechanical properties maintained constant even at the sample surface. After 240 h of LTD, the monoclinic phase was detected on all specimens by Raman peaks centered at 180, 191, and 383 cm^?1. The nanoindentation study revealed an important loss of mechanical features reaching 10 and 175 GPa for H and E, respectively. In the case of the ZS specimens, no monoclinic phase is detected after 240 h of LTD treatment and no decay of E or H is detected. The free defect microstructure reached for the ZS specimen revealed a higher hydrothermal resistance so that it is concluded that the excellent behavior against thermal degradation is possible due to the large uniformity obtained by colloidal processing rather than the particle size of the starting powders.     

Optimizing the performance of aerosol photoacoustic cells using a finite element model. Part 2: Application to a two-resonator cell

Abstract

Photoacoustic spectroscopy (PAS) measures aerosol absorption in a noncontact manner, providing accurate absorption measurements that are needed to improve aerosol optical property representations in climate models. Central to PAS is resonant amplification of the acoustic pressure wave generated from laser-heated aerosol transferring heat to surrounding gas by a photoacoustic cell. Although this cell amplifies pressure sources from aerosol absorption (signal), it also amplifies noise and background sources. It is important to maximize the cell signal-to-background ratio (SBR) for sensitive absorption measurements. Many researchers have adopted the two-resonator cell design described by Lack et al. (2006 Lack, D. A., E. R. Lovejoy, T. Baynard, A. Pettersson, and A. R. Ravishankara. 2006. Aerosol absorption measurement using photoacoustic spectroscopy: Sensitivity, calibration, and uncertainty developments. Aerosol Sci. Technol. 40 (9):697–708. doi: 10.1080/02786820600803917.[Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]). We show that the uncertainty in PAS measurements of aerosol absorption using this two-resonator cell is significantly degraded by its large sensitivity to background contributions from laser scattering and absorption at the cell windows. In Part 1, we described the use of a finite element method (FEM) to predict cell acoustic properties, validated this framework by comparing model predictions to measurements, and used FEM to test various strategies applied commonly to single-resonator cell optimization. In this second part, we apply FEM to understand the excitation of resonant modes of the two-resonator cell, with comparison measurements demonstrating accurate predictions of acoustic response. We perform geometry optimization studies to maximize the SBR and demonstrate that the laser–window interaction background is reduced to undetectable levels for an optimal cell. This optimized two-resonator cell will improve the sensitivity and accuracy of future aerosol absorption measurements.