Thermochemical investigations of associated solutions: calculation of solute--solvent equilibrium constants from solubility measurements.
A simple solution model that has lead to successful predictive equations for the partial molar excess properties of a solute in simple binary solvent mixtures containing only nonspecific interactions is extended to include association between the solute and one of the solvent components. An expression is derived and tested for its ability to describe anthracene solubilities in binary solvent mixtures containing benzene. The best description of the experimental solubilities requires the formation of a 1:1 anthracene-benzene complex, with a molarity-based equilibrium constant of KcAC approximately equal to 0.107 M-1. In comparison, a stoichiometric complexation model which attributes all solubility enhancement to the formation of anthracene-benzene complexes requires a somewhat larger equilibrium constant (KcAC approximately equal to 0.228 M-1) to describe the solubility behavior of anthracene in the benzene-n-heptane system. The results of these calculations illustrate that the determination of solute-solvent equilibrium constants from solubility data depends on the theoretical model used and the manner in which nonspecific interactions are incorporated into the model.
Solubility in binary solvent systems: 8. Estimation of binary alkane plus p-dioxane solvent nonideality from measured anthracene solubilities.
Experimental solubilities are reported for anthracene in binary solvent mixtures containing p-dioxane with n-hexane, cyclohexane, n-heptane, methylcyclohexane, n-octane, cyclooctane, and isooctane at 25 degrees C. Results of these measurements, used in conjunction with the nearly ideal binary solvent (NIBS) model, enabled excess Gibbs free energies, delta GBCfh, of the seven binary solvent mixtures to be estimated. Estimated values for p-dioxane plus cyclohexane, p-dioxane plus n-heptane, and p-dioxane plus methylcyclohexane mixtures are in reasonable agreement with published values based on vapor pressure measurements.
Enhancement of surface properties on Low Density Polyethylene packaging films using various fluorination routes
Nowadays, packaging market deployment requires an important attention. Influence of treatment with molecular (F2) or atomic (Fradical dot) fluorine on properties of Low Density Polyethylene (LDPE) films was investigated. The films were treated using direct fluorination conditions with F2 or a specific reagent XeF2, which releases atomic fluorine Fradical dot. Changes of LDPE chemical composition were investigated by FTIR and solid state NMR. Surface morphology was studied by several microscopy techniques (SEM and AFM). Finally to further characterize film properties after treatments, surface energy measurements and electron paramagnetic resonance (EPR) analyses were also carried out. An upper fluorinated layer, which contains mainly high amount of single bondCF2single bond, was formed during the direct fluorination conditions (F2). For the process performed with XeF2, specific groups single bondCHFsingle bond were detected not only on the polymer surface but also in the bulk. The final CHF/CF2 ratio depended on the fluorination route. Treatment with Fradical dot (originated from XeF2 decomposition) resulted in single bondCHFsingle bond groups in bulk prevailing formation whereas F2 formed mainly single bondCF2single bond groups. Regardless to the reactive species, radicals (dangling bonds) appeared during the fluorination and reacted with oxygen during the exposition to air after the treatment. Such a process resulted in oxygenated polar groups formation and consequently in the surface energy increase.