The effect of solvent and temperature on the miscibility of polystyrene (PS) and poly (styrene-co-acrylonitrile) (PSAN) was examined by the dilute-solution viscometry (DSV) method. The extent of miscibility of different PS/PSAN blend compositions (30/70, 50/50, and 70/30) in chloroform (CHCl3) and N, N- dimethyl formamide (DMF) was discussed in terms of the signs of various viscosity (ΔB, μ, Δ[η], α, and β) parameters. Based on the sign convention of these interaction parameters, partial miscibility in DMF and almost immiscibility in CHCl3 was indicated for the examined blend. The data obtained from the DSV method were then correlated with the ones obtained through density and refractive index measurements; good agreement was obtained. The study also revealed a relatively greater influence of temperature and composition on the miscibility of the blend in DMF than in CHCl3. 相似文献
Calculations were performed on the basis of a generalized Gibbs energy of mixing G, which is the sum of the Gibbs energy of mixing of the stagnant system and Es, the energy stored in the system during stationary flow. With increasing shear rate , the demixing temperatures shift to lower values (shear-induced mixing; diminution of the heterogeneous area), then to higher values (shear-induced demixing), and finally to lower values again before the effects fade out. The details of the rather complex phase diagrams resulting for a given shear rate are primarily determined by a band in the T/ plane ( = mole fraction) within which (2Es/2)T<0 (i.e., ES acts towards phase separation). There are two ranges of within which closed miscibility gaps can exist: The more common outer islands are partly or totally situated outside the equilibrium gap (and within the above mentioned band). As is raised they break away from the mainland at the upper end of the first region of shear-induced mixing and shift to T>UCST where they submerge. Bound to a suitable choice of parameters, a second kind of closed miscibility gaps, the inner islands, which always remain within the equilibrium solubility gap (and outside the band of negative curvature of ES) is additionally observed. This time the islands break away from the mainland at the lower end of the first region of shear-induced mixing where they also submerge. The present findings are compared with the results of previous calculations for LCSTs. 相似文献
This is the second of two joint papers which study the influence of several physical properties on the transport phenomena in chemical flooding. To that aim, we use a previously reported ternary two-phase model into which representative physical properties have been incorporated as concentration-dependent functions. Physical properties such as phase behavior, interfacial tensions, residual saturations, relative permeabilities, phase viscosities and wettability have been analyzed in the first paper.
In this paper, we discuss the influence of capillary pressure, adsorption of the chemical component onto the rock and dispersion. Although arising from different phenomenological sources, these transport mechanisms show some similar effects on concentration profiles and on oil recovery. They are studied for systems with different phase behavior. A numerical analysis is also presented in order to determine the relevance of the number of grid blocks taken in the discretization of the differential equations. This numerical analysis provides useful guidelines for the selection of the appropriate numerical grid in each type of displacement.
The phase behavior of several polycarbonate homopolymers and copolymers blended with PVC and chlorinated PVCs (CPVCs) has been investigated. Tetrachlorobisphenol-A polycarbonate (TCPC) is miscible in all proportions with PVC and CPVCs containing up to70.2 wt% chlorine. CPVCs having chlorine contents greater than 70.2% (by weight) are immiscible with TCPC. Tetrabromobisphenol-A polycarbonate (TBPC) exhibits phase mixing with PVC and CPVCs; however, the high Tg of this polycarbonate (260°C) prevents adequate investigation of equilibrium phase behavior. Bisphenol-A polycarbonate (BPC), tetramethylbisphenol-A polycarbonate (TMPC), and hexafluorobisphenol-A polycarbonate (HFPC) form two-phase mixtures with the vinyl polymers. Microstructural differences in the CPVCs due to chlorination method (solution chlorination vs. slurry chlorination) have no effect on the miscibility results. Miscibility was observed in several copolycarbonate/CPVC blends and was found to be dependent on copolymer composition. Using a binary interaction, mean-field theory, segmental interaction parameters were estimated for repeat unit interactions. Based on the estimated interaction parameters, miscibility in these blends is primarily the result of intramolecular repulsive effects, rather than strong intermolecular attractive forces.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献