Vapor sorption behavior

The effect of physical aging on the crystallization state and water vapor sorption behavior of amorphous non-solvated trehalose was studied [91]. It was found that annealing the amorphous substance at temperatures below the glass transition temperature caused nucleation in the sample that served to decrease the onset temperature of crystallization upon subsequent heating. Physical aging caused a decrease in the rate and extent of water vapor adsorption at low relative humidities, but water sorption could serve to remove the effects of physical aging due to a volume expansion that took place in conjunction with the adsorption process. 

Guerrieri P, Salameh AK, Taylor LS (2007) Effect of small levels of impurities on the water vapor sorption behavior of ranitidine HCl. Pharm Res 24(1) 147-156. 

Mohanty AK, Misra M, Drzal LT (2002) Sustainable bio-composites from renewable resources opportunities and challenges in the green materials world. J Polym Environ 10(l-2) 19-26 Hill CAS, Norton A, Newman G (2009) The water vapor sorption behavior of natural fibers. J Appl Polym Sci 112(3) 1524-1537... 

EXTRACT and O-METHYLATED EXTRACT. The sorption of benzene by the extract and the O-methylated extract is characterized by a rapid, initial uptake followed by a very slow approach to equilibrium. Such sorption behavior is very similar to that of glassy polymers. Thus we have chosen to interpret the sorption curves shown in Figures 2 and 3 in terms of the Berens-Hopfenberg model developed for the sorption of organic vapors into glassy polymers.(lS) By doing so, we attempt to correct the total sorption values for surface adsorption in order to calculate x parameters. 

In recent years the Coal Research Laboratory has been investigating the kinetics and isotherm behavior of methanol sorption on coal (6, 7, 10) along with the sorption of other vapors on coal (6) and of polar vapors on swelling gels (9, 10). Methanol sorption was shown to be reversible on coal, and its sorption behavior supports the model of coal as a gel or mixture of gels in its physical structure. All indications (I, 6, 7) are that its interaction is with specific and a fixed number of sites for a particular coal sample. Although the sorption of methanol is reversible, coal exhibits sorption behavior which is interpreted in terms of an irreversible swelling of the coal gel upon initial exposure to methanol vapor. As a result of these studies, an isotherm and experimental rate equation for the sorption and desorption were derived that fit the observed data. The isotherm derived for methanol sorption on coal was ... 

The complex sorption behavior of the water in amine-epoxy thermosets is discussed and related to depression of the mechanical properties. The hypothesized sorption modes and the corresponding mechanisms of plasticization are discussed on the basis of experimental vapor and liquid sorption tests, differential scanning calorimetry (DSC), thermomechanical analysis (TMA) and dynamic mechanical analysis. In particular, two different types of epoxy materials have been chosen low-performance systems of diglycidyl ether of bisphenol-A (DGEBA) cured with linear amines, and high-performance formulations based on aromatic amine-cured tetraglycidyldiamino diphenylmethane (TGDDM) which are commonly used as matrices for carbon fiber composites. 

When the solvent concentration is very small, as in the case of gas or low-activity vapor sorption, Eq. (1) becomes the limiting Henry s law and a linear sorption behavior is expected. 

However, only limited experimental studies on the thermodynamic properties of polypeptide solutions have been carried out. The results of vapor sorption studies for PBLG and poly(P-benzyl L-aspartate) solutions at high polymer concentrations by Flory and Leonard could not be explained by the Flory model, but could be explained by assuming that mixing of solvent with flexible side chains dominates the thermodynamic behavior at high concentrations. Rai and Miller obtained similar results for the PBLG-dimethylformamide (DMF) system at high concentrations. They also showed that the results could be explained by the Wee-MiUer theory in which modification of Flory s lattice theory to allow for side chain... 

Many methods of measuring water activity have been developed by researchers. These include direct vapor pressure measurement, equilibration with a stable hygroscopic substance that has a known sorption behavior, and various types of hygrometers (Doe, 1998). 

Spectroturbidimetry, conductimetry, ultrafiltration, ultracentrifugation, vapor sorption, polarizing microscopy, and nuclear magnetic resonance spectroscopy were used to study phase behavior of pure sodium 8-phenyl-n-hexadecyl-p-sulfonate in water as a function of temperature and sodium chloride concentration, and in decane. The first four techniques gave information on solubility and states of dispersion ranging from visible, settling suspensions to transparent, stably dispersed submicro-scopic particles. Surfactant solubility in water was only 0.06 wt% at 25°C, increased 11-fold at 90°C, but decreased 300-fold with 3 wt% salt at 25°C. The surfactant-rich phase in... 

Farnworth [14] reported a numerical model describing the combined heat and water-vapor transport through clothing. The assumptions in the model did not allow for the complexity of the moisture-sorption isotherm and the sorption kinetics of fibers. Wehner et al [30] presented two mechanical models to simulate the interaction between moisture sorption by fibers and moisture flux through the void spaces of a fabric. In the first model, diffusion within the fiber was considered to be so rapid that the fiber moisture content was always in equilibrium with the adjacent air. In the second model, the sorption kinetics of the fiber were assumed to follow Fickian diffusion. In these models, the effect of heat of sorption and the complicated sorption behavior of the fibers were neglected. 

The structural changes in the framework of the aluminomethylphosphonate AlMepO-P upon water vapor sorption and the location of the sorbed water molecules have been investigated using X-ray powder diffraction techniques. Only small differences between the framework structures of the degassed and the water-sorbed sample were found. However, the latter did contain additional water positions in the channels. The differences between the water sorption behavior of the two polymorphs of AlMepO (-a and P) are discussed. 

A humidity-sensitive conducting polymer actuator made up of PEDOT doped with poly(4-styrenesulfonate) (PEDOT/PSS) was fabricated [47]. Water vapor sorption and electro-active actuating behavior of free-standing PEDOT/PSS films were investigated by sorption isotherm and electromechanical analyses. The non-porous PEDOT/PSS film, with a specific surface area of 0.13 m g sorbed water vapor of 1,080 cm (STP)g , corresponding to 87 wt%, at relative water... 

A practically very useful method to investigate hydrates is dynamic vapor sorption (DVS) (see Section 8.2.3.2). It provides information on the water sorption behavior of substances, and while it is less suited than slurry experiments to obtain thermodynamic parameters of hydrates, it provides very valuable kinetic information. 

The miscibility behaviors of poly-D(—)(3-hydroxybutyrate) (PHB)/poly(ethylene oxide) (PEO) and PHB/poly(methyl methacrylate) (PMMA) blends have been studied using a chloroform vapor sorption technique [73]. The addition of PEO, which has been reported to be miscible with both PHB and PMMA, did not enhance the compatibility of PHB and PMMA. Polymer-polymer interaction parameters monitored by using the chloroform vapor sorption technique were found to be negative for PHB/PEO, but positive for PHB/PMMA systems. However, the interaction parameters of both systems were changed significantly depending on their composition. 

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