Sorption, polymers

For glassy polymers, sorption isotherms are more complex and hysteresis oetween the pressurization and depressurization steps may... 

Figure 7. Sorption steps and selective binding in case of simple polymers sorption processes take place comparable to effects occurring in separation columns. The different steps are demonstrated.

The ability of SCFs to dissolve to considerable extent into amorphous glassy polymers (polymer sorption) ... 

As discussed above for simple adsorption, polymer sorption can be treated in both thermodynamic and kinetic contexts. The quantity of an analyte that is sorbed by a polymer at equilibrium is referred to as the solubility of the analyte, while the rate at which the analyte is transported through the polymer is referred to as permeability. Although high solubility is generally a prerequisite for high permeability (on any reasonable time scale), there are some notable exceptions. Poly-siloxanes and polytetrafluoroethylene (Teflon ), for example, are quite permeable to water, but the solubility of water is not particularly large in either material. 

Figure 5.15 Typical sorption isotherms representing different polymer sorption models, as indicated.

The crystallites are impermeable to penetrants leading to a hindered diffusion (tortuosity effect). For a semicrystalline polymer, sorption of pure liquid is given by [36]... 

M. J. Pikal, D. A. Bibler, and B. Rutherford, Polymer sorption of nitroglycerin and stability of molded nitroglycerin tablets in unit-dose packaging, / Pharm. Sci. 66, 1293-1297(1977). 

The two examples above show that the model allows us to predict accurately the solubility of the blends when the pure polymer sorption isotherm for the solvent under investigation is known and the binary parameter associated with the polymer-polymer pair is set to its default value, as in the present cases. The results are more than satisfactory, with average errors that seldom exceed the value of 10% in the case of PS-TMPC blends and are generally even lower for the other blends considered. 

Given a reliable PVT description of polymer melts and their mixtures, the equilibrium behavior of a polymer with a gas phase was examined [Xie et al., 1992], During the last 20 years, studies of gas polymer sorption enjoyed great advances on two fronts ... 

Xenon-129 NMR as a Probe of Polymer Sorption Sites A New View of Structure and Transport... 

On Organic Polymers. Sorption on PVC, nylon, and Teflon is assumed to be the reason for a small loss of PH3 (including diffusion) when the gas is kept in tubes of these materials [40]. The percentage of PH3 (500 pg in Nj) sorbed on various sorts of flours and on starch, etc., are given in [4]. 

The book Porous Materials for Carbon Dioxide Capture is aimed at providing researchers with the most pertinent and up-to-date advances related to the fields of porous materials design and fabrication and subsequent evaluation in innovative cyclic CO2 adsorption processes, with special emphasis on uncovering the relationships between structural characteristics and CO2 capture performance. The book is divided into seven chapters that provide a resume of the current state of knowledge of porous CO2 capture materials, which include ionic liquid-derived carbonaceous adsorbents, porous carbons, metal-organic frameworks, porous aromatic frameworks, microporous organic polymers, sorption techniques such as cyclic calcination and carbonation reactions, and membrane separations. 

In this chapter, results of research template synthesis of bioinoiganic polymers on ions of transitive metals are discussed. The chemical stmc-ture of bioinorganic polymers, sorption properties and thermal-oxidative degradation are investigated. 

In Figure 6 a sorption isotherm for Polymer JR-400 on hair is presented. The data points represent values after contact times of 3 1/2 days. It should be pointed out that these measurements were carried out on a batch of hair different from that employed for the measurements of Figures 1, 2, etc., and somewhat higher sorptions were observed. The isotherm is typical of polymer sorption in the sense of possessing an apparent zero concentration adsorption intercept. However, a steady increase in sorption was observed with concentration, and no obvions plateau was evident (1). 

The form of polymer sorption isotherms has received mnch attention and many adsorption equations have been proposed and employed. In the present case, conformance was found with an equation of the Freundlich type ... 

Several features of the sorption of the polyeation by brown hair and, to a lesser extent, rayon and cotton snggest diffusion of the polymer into the fiber. First, the level of polymer sorbed by hair corresponds to several monolayers. (See Table 1.) By contrast, sorption onto the glass snbstrate closely approximates monolayer coverage. Second, the decrease in polymer sorption by hair that accompanies an increase in polymer MW is the reverse of that which is normally observed for the adsorption of polymers on nonporous solid interfaces. Finally, evidence for diffusion is found in the dependence of polymer sorption (M,) upon the sqnare root of time (t) for values of M,/M of up to 0.5 (Fig. 3). Crank (9) has shown that, in the simplest case where the sorption isotherm is linear, such a relationship always holds for diffusion of solnte from an infinite bath. 

---