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Solvent rich phase

Let us now consider a system composed of a polymer and a solvent. For compositions in between the inflection points, solvent molecules will diffuse into the solvent-rich phase, and the polymer molecules diffuse in the polymer-rich phase. Thus diffusion occurs against a concentration gradient. Therefore, this type of phase separation is known as up-hill diffusion. The up-hill diffusion leads to a spontaneous decomposition and it is therefore also named spinodal decomposition. The formation of two phases via spinodal decomposition occurs immediately upon reaching the spinodal decomposition region and does not require any activation energy. [Pg.172]

Graphically, the conditions for thermodynamic equilibrium are equal to two points which have a common tangent. These points give the composition of a polymer-rich phase (I) and a solvent-rich phase (II) that can coexist in thermodynamic equilibrium. The summation of such points is also called the coexistence curve or binodal line. [Pg.172]

In essence, the model divides a reactive polymer solution into a dispersed polymer-rich phase (phase 1), within which the concentration of functional groups is defined by the polymer morphology and structure, and a solvent-rich phase which contains no functional groups (phase 0). The individual polymer molecules are modeled as spheres of polymer-rich phase stuck at points of an imaginary lattice in solution. If the polymer concentration is sufficiently high, another phase enters the calculations which consists of overlapping polymer-rich spheres (phase 2). [Pg.200]

Extraction is a process whereby a mixture of several substances in the liquid phase is at least partially separated upon addition of a liquid solvent in which the original substances have different solubilities. When some of the original substances are solids, the process is called leaching. In a sense, the role of solvent in extraction is analogous to the role of enthalpy in distillation. The solvent-rich phase is called the extract, and the solvent-poor phase is called the raffinate. A high degree of separation may be achieved with several extraction stages in series, particularly in countercurrent flow. [Pg.459]

Extraction is the process of separating the constituents (solutes) of a liquid solution (feed) by contact with another insoluble liquid (solvent). During the liquid-liquid contact, the solutes will be distributed differently between the two liquid phases. By choosing a suitable solvent, you can selectively extract the desired products out of the feed solution into the solvent phase. After the extraction is completed, the solvent-rich phase is called the extract and the residual liquid from which solute has been removed is called the raffinate. [Pg.268]

An approximation to the miscibility limit in a binary system is obtained by assuming that the polar solvent is essentially insoluble in the hydrocarbon. Since the activity of the hydrocarbon in the hydrocarbon phase is near unity, at equilibrium it must be the same as that in the solvent-rich phase. [Pg.31]

Consider a polymeric species with degree of polymerization i in solution. The homogeneous solution can be caused to separate into two phases by decreasing the affinity of the solvent for the polymer by lowering the temperature or adding some poorer solvent, for example. If this is done carefully, a small quantity of polymer-rich phase will separate and will be in equilibrium with a larger volume of a solvent-rich phase. Tlie chemical potential of the i-mer will be the same in both phases at equilibrium, and the relevant Flory-Huggins expression is... [Pg.463]

If the volumes of the polymer rich and solvent-rich phases are V and V, respectively, then the fraction /, of t-mer that remains in the solvent-rich phases is given by... [Pg.463]

If the volume of the solvent-rich phase is much greater than that of the polymer-rich phase (R 1), then most of the smaller macromolecules will remain in the former phase (Eq. 12-33). Also, as i increases, the proportion of i-mer in the polymer-rich phase will increase. [Pg.464]

Figure 9.2 Schematic phase diagram of a polymer/solvent mixture, where y is the Flory chi parameter, and xe = 1/2 is x at the theta temperature. The quantity Xe X along the ordinate is a reduced temperature, and is the polymer volume fraction. CP is the critical point, and BL is the binodal line. SSL and KSL are the static symmetry line and the kinetic symmetry line, respectively. These lines define the phase-inversion boundaries during quenches. In quenches that end at the right of such a line, the polymer-rich phase is the continuous phase, while to the left of the line the solvent-rich phase is the continuous one. SSL applies at long times, after viscoelastic stresses have relaxed, while KSL applies at shorter times before relaxation of viscoelas-... Figure 9.2 Schematic phase diagram of a polymer/solvent mixture, where y is the Flory chi parameter, and xe = 1/2 is x at the theta temperature. The quantity Xe X along the ordinate is a reduced temperature, and <l> is the polymer volume fraction. CP is the critical point, and BL is the binodal line. SSL and KSL are the static symmetry line and the kinetic symmetry line, respectively. These lines define the phase-inversion boundaries during quenches. In quenches that end at the right of such a line, the polymer-rich phase is the continuous phase, while to the left of the line the solvent-rich phase is the continuous one. SSL applies at long times, after viscoelastic stresses have relaxed, while KSL applies at shorter times before relaxation of viscoelas-...
Figure 9.6 Coarsening process during phase separation of a polymer-rich phase (dark) from a solvent-rich phase (light). In the earliest period, image (b), the polymer-rich phase is the majority phase but eventually, in image (d), the majority phase is the solvent-rich one. The elastic stresses in the polymer-rich phase prevent it from... Figure 9.6 Coarsening process during phase separation of a polymer-rich phase (dark) from a solvent-rich phase (light). In the earliest period, image (b), the polymer-rich phase is the majority phase but eventually, in image (d), the majority phase is the solvent-rich one. The elastic stresses in the polymer-rich phase prevent it from...
Binary interaction parameters (Ay) and infinite dilution activity coefficients are available for a wide variety of binary pairs. Therefore the ratio of the solute infinite dilution coefficient in solvent-rich phase to that of the second phase ( ) will provide an estimate of the equilibrium distribution coefficient. The method can provide a reasonable estimate of the distribution coefficient for dilute cases. [Pg.485]

Water-rich phase Solvent-rich phase ... [Pg.792]

A chain in a poor solvent collapses into a globule with significant amounts of solvent inside. Most chains agglomerate with other chains and precipitate from solution. Only a very small number of polymers remain in the solvent-rich phase of a poor solvent in a globular conformation described by Fq (3,131) Far below the <9-temperatnre, the attraction dominates... [Pg.125]

Polymer-solvent mixtures can be separated and the polymer recovered from solution at the lower critical solution temperature (LCST). This is the temperature at which the miscible polymer-solvent mixture separates into a polymer-rich phase and a solvent-rich phase. LCST phenomena are related to the chemical nature of the mixture components, the molecular weight of the mixture components, especially the polymer, and the critical temperature and critical pressure of the solvent (Allen and Baker, 1965). As the single-phase polymer solution is isobarically heated to conditions near the critical point of the solvent, the polymer and solvent thermally expand at different rates. This means their free volumes change at different rates (Patterson, 1969). The thermal expansion of the solvent is much greater than that of the polymer. Near its critical point, the solvent has expanded so much that it is no longer able to solubilize the polymer. Hence, the polymer falls out of solution. If the molecular weight of the polymer is on the order of 10 a polymer-solvent LCST can occur within about 20-30°C of the solvent s critical temperature. If the molecular weight of the polymer is closer to 10, the LCST phase... [Pg.140]

Figure 9.4 shows a schematic diagram of the phase behavior of a semicrystalline polymer having a narrow molecular weight distribution. The two-phase envelopes located beneath the liquid-gas, critical mixture curve represent equilibrium between a molten, polymer-rich phase and a compressed, solvent-rich phase. If the pressure is isothermally increased to a point above the two-phase envelope, the liquid and gas phases merge to form a single homogeneous phase. As described in some detail in chapter 3, the border... [Pg.199]

In liquid extraction, sometimes called solvent extraction, a mixture of two components is treated by a solvent that preferentially dissolves one or more of the components in the mixture. The mixture so treated is called the raffinate and the solvent-rich phase is called the extract. The component transferred from raffinate to extract is the solute, and the eomponent left behind in the raffinate is the diluent. The solvent in the extract leaving the extractor is usually recovered and reused. In extraction of solids, or leaching, soluble material is dissolved from its mixture with an inert solid by means of a liquid solvent. The dissolved material, or solute, can then be recovered by crystallization or evaporation. Crystallization is used to obtain materials in attractive and uniform crystals of good purity, separating a solute from a melt or a solution and leaving impurities behind. [Pg.496]


See other pages where Solvent rich phase is mentioned: [Pg.168]    [Pg.239]    [Pg.233]    [Pg.260]    [Pg.138]    [Pg.140]    [Pg.174]    [Pg.463]    [Pg.633]    [Pg.648]    [Pg.649]    [Pg.45]    [Pg.398]    [Pg.483]    [Pg.459]    [Pg.592]    [Pg.592]    [Pg.592]    [Pg.594]    [Pg.46]    [Pg.125]    [Pg.141]    [Pg.142]    [Pg.142]    [Pg.280]    [Pg.282]    [Pg.439]    [Pg.443]    [Pg.97]   
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