Sorption of solvents

Another interesting case is the much higher solvent resistance of the P crystalline form of s-PS, with respect to the other ones. In fact, it has been found that the sorption of solvents (which are suitable to produce transformations from the a or the y form toward clathrate structures) occurs only in the amorphous phase, for the case of P form samples [122-124]. Sorption kinetic curves of liquid methylene chloride in s-PS samples in the a and p form are, for instance, compared in Fig. 21 [124]. 

One of the biggest problems with present-day septum inlet systems is that of septum bleed. Kolloff (13) was the first to note the bleed of monomers and short-chain polymers (used in the production of the synthetic elastomers from which septa are derived) from gas chromatographic septa. Another problem is sorption of solvents and sample components on the septa. A thorough study of this phenomena was made by Adler (14) related to the use of selfsealing elastomer septa for quantitative operations with volatile laboratory solvents. It was found that a silicone septum could absorb over twice its weight of carbon tetrachloride and chloroform and more than its weight of benzene at 25°C. 

SORPTION OF SOLVENT MIXTURES IN ION EXCHANGE RESINS INFLUENCE OF ELASTIC PROPERTIES ON SWELLING EQUILIBRIUM AND KINETICS... 

It has been recognized for some time that the kinetics of sorption of solvents into glassy polymers vary in form with the penetrant activity Fickian, anomalous, and Case II kinetics may be observed as activity is increased in a given solvent/polymer system (13). The recent study of several organic liquid and vapor penetrants in rigid PVC indicates that the the interaction parameter and plasticizing efficiency of the penetrant, as well as its activity, are factors affecting the form of the sorption kinetics (4). 

The partition and displacement model considers retention to result from a two step process. The first involves formation of a mixed stationary phase by intercalation of solvent molecules from the mobile phase. The composition of the solvents in the stationary phase is established according to thermodynamic equilibrium and is usually different to the bulk mobile phase composition. Competitive sorption of solvents is modeled as a displacement process and is complete before the solute is introduced into the two-phase system. Solute retention is then modeled as a partition process between the solvent modified stationary phase and the mobile phase by taking into account all solute-solvent interactions in both phases. The phenomenological model of solvent effects attempts to model retention as a combination of solute-solvent interactions (the solvation effect) and solvent-solvent interactions (the general medium... 

Cosolvent-enhanced electrokinetic remediation of chlorinated pesticides has yet to be explored. Few studies have shown enhancements in the transport of polycyclic aromatic hydrocarbons (PAHs) when cosolvents were used (Maturi and Reddy, 2008 Reddy and Saichek, 2003). The potential success of cosolvents depends on their ability to mobilize the HOCs and to increase the EOF. It was shown that 10% n-butylamine generated the greatest EOF, followed by 20% n-butylamine and water (Maturi and Reddy, 2008). The sorption of solvents to the soil matrix may not be as high as the surfactants, which cause a better solubilization with the same amount of electro-osmotic transport. 

An initial increase and subsequent decrease of the diffusion coefficient of an antioxidant [167] and analogical picture obtained for sorption of solvents [168] in relation to the degree of crosslinking of LDPE was interpreted as being due two counter-acting effects, namely by a reduction in crystallinity and by an increase of packing of amorphous regions. 

A.A. Tager [110] determined the change of AG k by producing thermodynamic cycles using static sorption of solvent vapors on the polymeric specimens. However, in solution the polymer compatibihty is influenced by the difference of the thermodynamic interaction parameters of the common solvent with each indvidual polymer. Additionally, compatibility in solution does not always correspond to that in the solid state (without a solvent). These shortcomings limit the applicability of the AG ix estimation method that Tager developed. 

The mass change increases with the number of cycles due to the gradual swelling of the film. In the negative potential region (N), irreversible mass and charge increases occur due to the sorption of solvent molecules [65],... 

Chloroprene Single Tg when I had 18 % acrylonitrile sorption of solvent vapors Two phases in electron micrograph when I had 18 % acrylonitrile may indicate a crystalline phase two torsional transitions when I had >28 % acrylonitrile Casper and Morbitzer (1977), Tager et aL (1987)... 

Mahesh K P O, Tsujita Y, Yoshimizu H, Okamoto S, Mohan D J (2005) Study on 6-form complex in syndiotactic polystyrene-organic molecules systems. IV. Eormation of complexes with a mixture of solvents and structural changes during the sorption of solvents by syndiotactic polystyrene mesophase membranes. J. Polym. Sci. Part B Polym. Phys. 43 2380-2387... 

Sorption of solvents through the membrane depends much more on Langmuir sorption than on Henry s Law. Solubility of solvent in membrane is usually very small (less than 1%). The permeability coefficients of solvents correlate with the longest molecular dimension of solvents. The permeation flux through the film is given by the following equation ... 

PTFE is inert to essentially all common chemicals (see Refs. 64 and 65). It is, however, attacked by molten alkali metals, elemental fluorine, and pure oxygen at elevated temperatures, it can also react under some conditions with alkaline earth oxides and finely divided metals such as aluminum or magnesium at elevated temperature. Sorption of solvents is mentioned in Note 13. Solutions containing 0.1-2% PTFE were obtained in perfluoroker-osene C2iF44(FCX-412) in the temperature range 290-310°C (see Refs. 71 and 74). 

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