Fundamental thermo‐mechanical property modeling of triglyceride‐based thermosetting resins

The glass transition temperature (T_g) of acrylated triglycerides was clearly a function of the level of acrylation of triglyceride‐based polymers and was modeled using simple empirical relationships. We began by calculating the distribution of unsaturation sites in plant oils. We assumed a binomial distribution of chemical functionality that was added to these unsaturation sites to calculate the distribution of epoxides, acrylates, and reacted acrylates to predict the crosslink density, thermal softening, and dynamic mechanical behavior. The glass transition temperatures of n‐acrylated triglycerides were used as the relaxation temperatures of acrylated oils with a broad distribution of functionality for prediction of the modulus as a function of temperature. Essentially, the percent drop in the elastic modulus is equal to the percentage of n‐acrylated triglycerides in the acrylated oil with T_g less than that of the ambient temperature. The tan (δ) was also accurately predicted based on the percentage change of n‐functional triglycerides as the temperature changes from one relaxation temperature to the next. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Morphological and Elemental Classification of Freshly Emitted Soot Particles and Atmospheric Ultrafine Particles using the TEM/EDS

The Transmission Electron Microscopy (TEM) and Energy Dispersive Spectroscopy (EDS) were used to determine morphology and elemental composition of a variety of freshly emitted soot particles (acetylene flame, candle flame, kerosene flame, diesel exhaust, electric arc, plastic burning, styrofoam burning, wood burning [white oak and pine bark], and rice straw burning), which can be possible candidate soot in the ambient atmosphere, and ultrafine particles sampled in urban, industrial, and coastal sites during ultrafine particle formation events (combustion and photochemical events). By using mobility-classified non-refractory ((NH ₄ ) ₂ SO ₄ ) and refractory (Polystyrene latex (PSL) and salt (NaCl)) particles, limitation of the TEM was tested. Data showed that the TEM method can be used to examine shapes of both volatile particles such as (NH ₄ ) ₂ SO ₄ (100 nm) at low, but not high magnification (refer to low and high beam intensity, respectively), and non-volatile particles like NaCl (100 nm) and PSL (84 nm) at either low or high magnification. Distinct differences in morphological properties such as primary particle diameter, fractal dimension, and microstructure were observed among the different types of fresh soot particles. The atmospheric ultrafine particles were classified as agglomerates, sulfate mixtures (spherical), metallic oxides (spherical and polygonal), C-rich refractory (not agglomerated), C-rich non-refractory (not agglomerated), Si-rich (spherical), Na-rich (porous), or P-containing (non-spherical) particles. At the urban Gwangju site, a higher fraction of fresh and aged agglomerates was observed than at other sites. The C-rich non-refractory and sulfate mixtures were often observed in the photochemical event. The C-rich refractory particles were abundant at the Gwangju and Yeosu sites. The coastal Taean site had few agglomerates due to limited anthropogenic combustion source.     

Spatial Measurements of Ultrafine Particles Using an Engine Exhaust Particle SizerTM within a Local Community Downwind of a Major International Trade Bridge in Buffalo,New York

Ultrafine particles (UFP) can be defined as having at least one dimension that is less than 100 nanometers. Because of their dimensions, they exhibit unique properties that affect atmospheric transport, exposures, and possibly health endpoints. Freshly generated Diesel particulate matter (DPM) is predominantly in the ultrafine particle size range size range, which in practice is defined by the detection characteristics of the sampling instrument. During two seasons, an Engine Exhaust Particle Sizer^TM (TSI, St. Paul, MN) detects particles over a range of 5.6–560 nm was used to continuously measure real-time particle size distributions along several streets that extend from the Peace Bridge (PB), a major international trade bridge, into a the nearby adjacent neighborhood that has reported a high prevalence rate of asthma (Lwebuga-Mukasa 2000). The Peace Bridge connects Buffalo, NY, USA to Fort Erie, ON, Canada. During summer 2004, one minute average particle number concentrations were continuously monitored along neighborhood streets near the Peace Bridge Complex (PBC) plaza out to about 2 km. Ultrafine particle counts as a function of bridge traffic showed downwind UFP levels at 300 m ranging from 60,000–70,000 p/cm³. Upwind background UFP levels at the shore line of Lake Erie were typically 8,000–10,000 p/cm³ under similar traffic and meteorological conditions. During winter 2006, additional measurements were conducted in front of several homes that were part of a separate indoor-outdoor exposure study (McAuley et al. 2010 McAuley, T. R., Fisher, R., Zhou, X., Jaques, P. A. and Ferro, A. R. 2010. Relationships of Outdoor and Indoor Ultrafine Particles at Residences Downwind of a Major International Border Crossing in Buffalo, NY.. Indoor Air, 20: 298–308. [Crossref] , [Google Scholar]). Sampling at the homes was done during the weekdays when heavy diesel truck traffic was highest. Results showed that most of the UFP number concentrations fell between 10–20 nm in front of homes with UFP levels ranging from 59,000 p/cm³ at couple hundred m downwind to 81,000 p/cm³ several hundred m directly downwind of the Peace Bridge under similar diesel trucks traffic and meteorological conditions.     

Diffusion-Limited Versus Quasi-Equilibrium Aerosol Growth

Condensation of gas-phase material onto particulate matter is the predominant route by which atmospheric aerosols evolve. The traditional approach to representing formation of secondary organic aerosols (SOAs) is to assume instantaneous partitioning equilibrium of semivolatile organic compounds between gas and particle phases. Growth occurs as the vapor concentration of the species increases owing to gas-phase chemistry. The fundamental mathematical basis of such a condensation growth mechanism (quasi-equilibrium growth) has been lacking. Analytical solutions for the evolution of an organic aerosol size distribution undergoing quasi-equilibrium growth and irreversible diffusion-limited growth are obtained for open and closed systems. The quasi-equilibrium growth emerges as a limiting case for semivolatile species condensation when the rate of change of the ambient vapor concentration is slow compared with the rate of establishment of local gas-aerosol equilibrium. The results suggest that the growth mechanism in a particular situation might be inferred from the characteristics of the evolving size distribution. In certain conditions, a bimodal size distribution can occur during the condensation of a single species on an initially unimodal distribution.

Copyright 2012 American Association for Aerosol Research     

Enhancement of Surfactants in Nanoparticles Produced by an Electrospray Aerosol Generator

Electrospray aerosol generators (EAGs) disperse conducting solutions into air, promptly neutralize the particles to remove the excess charge, and evaporate the residual solvent with a dry air flow. For solutions containing multiple solutes, the particles may become enhanced in the more surface-active solutes. The extent of the enhancement was estimated for nanoparticles electrosprayed from a solution containing NaCl and surfactant sodium dodecyl sulfate (SDS) mixed in a 9:1 weight ratio. A tandem particle mobility analyzer was used to quantify the hygroscopic growth factor (GF). The relative fractions of NaCl and SDS in the particles were estimated from the measured GFs assuming that NaCl and SDS take up water independently of each other. The nanoparticles were considerably enhanced in SDS relative to the starting solution, with the NaCl:SDS weight ratio increasing with the distance from the EAG electrified capillary tip to the neutralizer, and reaching ～1:1 at the longest distances probed. The enhancement in SDS likely occurred during particle fission events as particles traveled from the capillary to the neutralizer. This study has practical ramifications for aerosol nanotechnology and aerosol-assisted drug delivery, which rely on EAG as an instrument of choice for nanoparticle generation.

Copyright 2012 American Association for Aerosol Research     

Effect of Dipping Temperature and Dipping Time on Drying Rate and Color Change of Grapes

Thompson seedless grapes (Vitis vinifera) were pretreated in potassium carbonate and ethyl oleate solutions for 1, 2, and 3 min at 30, 40, 50, and 60°C and dried in a convective air dryer at 60°C. The effect of dipping time and solution temperature on drying rate and color kinetics were investigated. Grapes dipped into the solution at 60°C for 2 and 3 min had the fastest drying rate. Among the seven semi theoretical models compared, the Midilli equation best described the drying curves of grapes for all dipping pretreatments. Color data were obtained using a machine vision system in CIE L*a*b* color space. Regardless of the dipping time and temperature applied, all raisins had varying degrees of brown coloring. At all dipping times and temperatures the highest R ² value was obtained for a* values, which followed zero-order reaction kinetics during drying.     

Comparative Bounce Properties of Particle Materials

A test impactor with a 10-μm 50% cutoff diameter at a flow rate of 7 liters/min was designed to measure particle bounce by the observed penetration to an optical counter. The effects of surface loading and relative humidity on particle bounce were determined, and a set of test criteria was developed to avoid these effects. The particle bouncing experiments were performed for ten common aerosols: ammonium fluorescein, sodium chloride, ammonium sulfate, potassium biphthalate, polystyrene latex, lycopodium spores, paper mulberry pollen, short ragweed pollen, glass beads, and Pinole soil. The differences in the fraction of bounce for different particle materials are discussed. Systematic measurements for ammonium fluorescein revealed a correlation between the fraction of particles bouncing and the particle kinetic energy and aerodynamic diameter. The EPA bounce criterion for PM ₁₀ samplers is criticized in terms of this correlation.     

Composition and Size Distribution of Residential Wood Smoke Particles

Residential wood combustion emissions are an important source of organic and elemental carbon particulate matter in many urban and suburban areas. This research determined the organic and elemental carbon composition and size distribution of particulate emissions for hot- and cool-burning wood stoves and from conventional fireplaces. Sampling was done from smoke plumes which had been cooled and diluted by ambient air so that the particulate composition measured would be representative of smoke particles as they actually exist in the atmosphere. Organic and elemental carbon were determined by thermo-optical carbon analysis. Corrections were made for vapor organic carbon adsorption on quartz fiber filters during sampling. Particles emitted by hot-burning stoves were black, had a unimodal size distribution, and contained from 20% to 60% carbon (primarily elemental carbon) and high levels of trace elements (11% K, 1% S, 3% Cl). In contrast, particles from cool-burning stoves were tan, had a bimodal size distribution, and contained from 55% to 60% carbon (almost entirely organic carbon) and minute amounts (< 0.1%) of trace elements. The composition of particles emitted by fireplaces had compositions that were intermediate between those of hot- and cool-burning stoves, but tended to be more similar to cool burning stove emissions.     

Aerosol Dynamics in Atmospheric Aromatic Photooxidation

Aerosol formation and growth in aromatic hydrocarbon / NO_x systems was studied in a series of outdoor smog chamber experiments. Analysis of the aerosol size distributions in those experiments that exhibited steady condensational growth provides estimates for the gas-phase partial pressures of the condensing species. Saturation ratios during these growth periods are estimated by comparing these partial pressures with vapor pressures obtained from an analysis of nucleation (Stern et al., 1987), and are found to be in the range of 5 to 20. Modeling of the size–distribution dynamics during the experiments is carried out using the sectional model ESMAP (Warren and Seinfeld, 1985). The full size-distribution model predicts more nucleation than an integral model (Stern et al., 1987), because the polydisperse aerosol representation leads to a lower condensation rate than that predicted for a monodisperse aerosol.     

Complete Recovery of Actinides from UREX-like Raffinates Using a Combination of Hard and Soft Donor Ligands. II. Soft Donor Structure Variation

The feasibility of simultaneous separation of uranium, neptunium, plutonium, americium, and curium from a simulated dissolved used fuel simulant adjusted to 1.0 M nitric acid is investigated using a mixture of the soft donor bis(bis-3,5-trifluoromethyl)phenyl) dithiophosphinic acid (“0”) and the hard donor synergist trioctylphosphine oxide (TOPO) dissolved in toluene. The results reported in this work are compared to our recent demonstration of a complete actinide recovery from a simulated dissolved fuel solution using a synergistic combination of bis(o-trifluoromethylphenyl)dithiophosphinic acid (“1”) and TOPO dissolved in either toluene or trifluoromethylphenyl sulfone. While the extraction efficiency of americium was enhanced for the liquid-liquid system containing “0”, enabling to accomplish a trivalent An/Ln separation at 1.0 M HNO₃, the extraction of neptunium was drastically diminished, relative to “1”. The partitioning behavior of curium was also negatively impacted, introducing an effective opportunity for americium/curium separation. Radiometric and spectrophotometric studies demonstrate that the complete actinide recovery using the solvent based upon “0” and TOPO is not feasible. In addition, the importance of radiolytic degradation processes is discussed through the comparisons of extraction properties of liquid-liquid systems based on both soft donor reagents.