Search results for "volume fraction"
showing 10 items of 87 documents
Physico-chemical properties of dense water/copper(II) bis(2-ethylhexyl) sulfosuccinate/CCl4 microemulsions
2007
Measurements of some physico-chemical properties (density, viscosity, conductance, infra-red spectra) of water/copper(II) bis(2-ethylhexyl) sulfosuccinate (Cu(DEHSS)2)/CCl4 microemulsions, as a function of the volume fraction O of the dispersed phase (0 < O < 0.6) and of the molar ratio R (R = [water]/[DEHSS−]), have been performed at 25 °C. At each value of R, the density of the micellar phase is practically independent of O whereas the viscosity of microemulsions diverges above threshold O values. A divergent behavior for the electrical conductivity has also been observed but only at certain R values. These results, together with those from infra-red spectra, suggest that in percolated mi…
Linear versus Three-Arm Star Polybutadiene: Effects of Polymer Architecture on the Thermodynamic Solution Behavior
2012
The interaction of linear and of three-arm star polybutadiene (PB) with THF was studied in the temperature range between 25 and 55 °C. Information for dilute solution rests on light scattering experiments; Flory–Huggins interaction parameter χ stem from vapor pressure measurements as a function of φ, the volume fraction of polymer. Despite the minute divergence in the architecture, the second osmotic virial coefficients of the two PBs differ noticeably. The present work demonstrates that these disparities become much more pronounced as φ increases and that they depend strongly on temperature. These findings are interpreted on the basis of an approach accounting for the effects of chain conn…
Effects of particle clustering on the plastic deformation and damage initiation of particulate reinforced composite utilizing X-ray CT data and finit…
2018
In this paper, a new simulation technique which can include microstructural inhomogeneity of particulate reinforced composites is proposed to accurately study deformation pattern and damage mechanism in these composites. Three dimensional microstructures constructed from XCT images incorporated into finite element modeling codes with minimal approximation to capture the effects of cluster size, local volume fraction of particles in the cluster and the distance between clusters as relevant statistical quantities describing the microstructural inhomogeneity of particulate reinforced composites. A quantitative parameter as degree of clustering is defined to consider particle clustering effect.…
Prediction of the retention in reversed-phase liquid chromatography using solute-mobile phase-stationary phase polarity parameters.
2002
Abstract A previously reported algorithm, based on the equation: log k=( log k) 0 +p(P N m −P N s ) , that relates the retention in reversed-phase liquid chromatography with solute (p), mobile phase (PmN) and stationary phase (PsN) relative polarity parameters, is improved. The retention data reported by several authors for different sets of compounds, eluted with acetonitrile–water and methanol–water mixtures, are used to test the algorithm and elaborate a database of p values. The methodology is successfully applied to predict the retention using PmN values calculated as PmN=1.00−(2.13ϕ)/(1+1.42ϕ) for acetonitrile–water and PmN=1.00−(1.33ϕ)/(1+0.47ϕ) for methanol–water, ϕ being the organi…
On what terms and why the thermodynamic properties of polymer solutions depend on chain length up to the melt
2003
Theoretical considerations based on chain connectivity and conformational variability of polymers have lead to an uncomplicated relation for the dependence of the Flory-Huggins interaction parameter, chi, on the volume fraction of the polymer, phi, and on its number of segments, N. The validity of this expression is being tested extensively by means of vapor pressure measurements and inverse gas chromatography (complemented by osmotic and light scattering data from literature) for solutions of poly(dimethylsiloxane) in the thermodynamically vastly different solvents n-octane (n-C8), toluene (TL), and methylethylketone (MEK) over the entire range of composition for at least six different mol…
Free energy of solvation of solutes and their partition coefficients in methanol-water binary mixtures
2001
A method is presented that permits semiquantitative estimation of the partitioning of any solute between any two media. The method is adapted to the simulation of multicomponent solvents. As an example, the free energies of solvation ΔG solv,aq o in methanol-water binary mixtures and the partition coefficientsP for organic solvent—aqueous solvent were calculated. The organic solvents studied were 1-octanol, cyclohexane and chloroform. Linear relationships were observed between the relative dielectric constant and the volume fraction of methanol in mixtures with water. The four hydrocarbon models studied were hexane, cyclohexane, hexatriene and benzene. The results are in agreement with calc…
Equilibrium and transport properties of ion-exchange membranes
1984
Abstract Specific properties (ion-exchange capacity, water content, pore volume fraction) and transport properties (counterion transport number and electrical conductivity) have been measured in four commercial cation-exchange membranes loaded with a variety of cations of different nature and charge. Not surprisingly, equivalent conductances are lower than in free solution and transport numbers decrease with valency of the counterion. This behavior is explained by taking into account a “tortuosity factor”, due to a lengthening of the pores across the membrane, except for a membrane with a lower water content and for ions of higher charge, in which electrostatic interactions between mobile a…
Polymer induced changes of the crystallization scenario in suspensions of hard sphere like microgel particles
2012
We investigated the crystallization scenario of highly cross linked polystyrene particles dispersed in the good solvent 2-ethylnaphtalene and their mixtures with non-adsorbing low molecular weight polysterene polymer using time resolved static light scattering. The samples were prepared slightly below the melting volume fraction of the polymer free system. For the polymer free samples, we obtained polycrystalline solids via crystallization scenario known from hard sphere suspensions with little competition of wall crystal formation. Addition of non-adsorbing low molecular weight polystyrene polymer leads to a considerably slowing down of the bulk crystallization kinetics. We observed a dela…
Diffusion of spherical micronetworks in polymer diluent systems and melts studied by dynamic light scattering techniques
1994
Spherical polystyrene (PS) micronetworks can be prepared in microemulsion with bulk radii of 5–60 nm and different cross-linking densities. The diffusion of these PS spheres has been studied in polymer diluent systems ranging from dilute solutions to plasticized melts by using forced Rayleigh scattering and photon correlation spectroscopy. On increasing the PS concentration, a colloid glass transition is observed at a volume fraction ΦC ≈ 0.64 of the swollen spheres. At higher concentration inside the “colloid glass” state the sphere diffusion is slowed down and becomes very complex but can be observed up to the limit of a melt of collapsed spheres.
Orientational ordering transitions of semiflexible polymers in thin films: A Monte Carlo simulation
2011
Athermal solutions (from dilute to concentrated) of semiflexible macromolecules confined in a film of thickness D between two hard walls are studied by means of grand-canonical lattice Monte Carlo simulation using the bond fluctuation model. This system exhibits two phase transitions as a function of the thickness of the film and polymer volume fraction. One of them is the bulk isotropic-nematic first-order transition, which ends in a critical point on decreasing the film thickness. The chemical potential at this transition decreases with decreasing film thickness ("capillary nematization"). The other transition is a continuous (or very weakly first-order) transition in the layers adjacent …