Search results for "Diagram"
showing 10 items of 795 documents
Calculation of phase diagrams not requiring the derivatives of the Gibbs energy for multinary mixtures
1996
A method for the calculation of phase diagrams (tie lines and binodal, spinodal, critical points and their stability) based exclusively on the Gibbs energy of mixing with no need of its derivatives with respect to the composition variables is extended to multinary mixtures for any number of components. The mathematical description of the (K-1)-dimensional phase diagram of a K-component mixture is presented. The method is demonstrated for a quinternary blend of five polymers exhibiting a closed miscibility gap; all binary, ternary and quaternary subsystems are completely miscible. The phase separation in the quinternary system is caused by very favorable interactions in the ternary subsystem…
Continuous fractionation and solution properties of PIB. I. Search for the best mixed solvent and first results of the continuous polymer fractionati…
1987
To adopt a recently developed method for large scale fractionation (CPF = continuous polymer fractionation, a special kind of counter current extraction) to polyisobutylene (PIB), a systematic search for the best mixed solvent was performed. For this purpose, the essential parts of the phase diagrams solvent/nonsolvent/PIB were determined for 21 mixed solvents by cloud-point measurements; with eight systems of special interest, the molecular weight distributions of the polymers contained in the coexisting phases were also studied. On the basis of these experiments and of considerations concerning additional criteria for the performance of the continuous counter current extraction, the mixed…
Phase behavior of the system hyperbranched polyglycerol+methanol+carbon dioxide
2010
Abstract Phase equilibrium data have been measured for the ternary system hyperbranched polyglycerol + methanol + carbon dioxide at temperatures of 313–450 K and pressures up to 13.5 MPa. Phase changes were determined according to a synthetic method using the Cailletet setup. At elevated temperatures the system shows a liquid–liquid–vapor region with lower solution temperatures. Besides the vapor–liquid and liquid–liquid equilibria, the vapor–liquid to vapor–liquid–liquid and vapor–liquid–liquid to liquid–liquid phase boundaries are reported at different polymer molar masses and can serve as test sets for thermodynamic models. A distinct influence of the polymer molar mass on the vapor–liqu…
Lattice fluid model generalized for specific interactions: An application to ternary polymer solutions
2011
Abstract The phase diagram of the Poly- l -Lactic-Acid (PLLA), dioxane and water system was derived by using the lattice fluid model generalized for specific interactions. A qualitative analysis of Hansen solubility parameters together with empirical observations were adopted to reduce the number of adjustable parameters. The as-selected model parameters were derived by fitting a set of cloud point curves; consequently, the complete phase diagram of the system was computed. The use of specific interactions between species gave out a quantitative agreement with a set of experimental data, whereas changing the polymer polydispersity the agreement is only qualitative. In principle, the present…
The effect of pressure on the liquid–liquid phase equilibrium of two polydisperse polyalkylsiloxane blends
2002
The effect of pressure-induced immiscibility in polymer blends is investigated by experimental and theoretical methods. Experimental data of cloud point curves and critical points are obtained by turbidity measurements. The chosen system is a mixture of polydimethylsiloxane and polyhexylmethylsiloxane which is one of the very few polymer blends exhibiting pressure-induced immiscibility. This unusual behaviour is related to a critical temperature minimum of the critical curve and cloud point isopleths at positive pressure in the temperature–pressure diagram. The effect of the chain length on the critical temperature minimum is investigated here based on theoretical models. The effect of diff…
Quick and reliable routes to phase diagrams for polyethersulfone and polysulfone membrane formation
2000
Phase diagrams were measured and calculated for the ternary membrane forming systems DMF/water/polysulfone and DMF/water/polyethersulfone at different temperatures. Customary experiments yielded cloud point curves, tie lines, and critical compositions. The theoretical computation starts from the Flory-Huggins theory and employs binary interaction parameters g ij that vary with the composition. This information was mainly obtained by means of Headspace-Gas Chromatography (HSGC, yielding the partial pressures of the volatile components); these data were complemented by light scattering and swelling experiments. The calculation of binodals, spinodals, tie lines, and critical points avoids the …
Shear Effects on the Phase Diagrams of Solutions of Highly Incompatible Polymers in a Common Solvent. 2. Experiment and Theory
1997
Cloud point temperatures (Tcp) were measured at different constant shear rates for three representatives of the ternary system cyclohexanone/polystyrene/poly(n-butyl methacrylate) (CHO/PS/PBMA) by means of a newly constructed rheo-optical apparatus that can be operated in the temperature range from 0 to 100 °C up to maximum shear rates of 1440 s-1 and maximum stresses of 384 Pa. In all cases one observes an extension of the homogeneous region as the shear rate γ is raised. With the system CHO/PS 196w/PBMA 2050 (the figures denote the molar masses of the polymers in kilograms/mole) the effects become maximum for high concentrations of PBMA, where the demixing temperatures increase by more th…
Shear Effects on the Phase Diagrams of Solutions of Highly Incompatible Polymers in a Common Solvent. 1. Equilibrium Behavior and Rheological Propert…
1997
Phase diagrams (cloud points, tie lines, critical compositions) and viscosities of homogeneous solutions were determined at temperatures ranging from 20 to 100 °C for three representatives of the ternary system cyclohexanone/polystyrene/poly(n-butyl methacrylate) [CHO/PS/PBMA] in preparation of a study on shear influences. An only moderate increase of the two-phase region observed upon heating (LCST behavior) witnesses little heat effects upon mixing. Tie lines which are nearly parallel to the PS/PBMA edge of the Gibbs phase triangle indicate comparable solvent quality of CHO for both polymers. The quantitative mathematical description of the equilibrium behavior-required for a theoretical …
Ternary Polymer Solutions with Hydrogen Bonds, 2
2007
Experimental ternary phase diagrams for ternary systems CHL/PS-MAA/PVPy with diverse MAA contents have been determined by GPC. The presence of MAA in the copolymers gives rise to specific interactions, by hydrogen bond formation between both polymeric components, so strong that the isotherm for the system with the highest MAA content so far studied, CHL/PS-MAA(8%)/PVPy, is representative of a complex coacervation situation. By applying the theoretical background deduced by coupling the Flory-Huggins lattice model to the AET developed for ternary polymeric systems SPP with specific intermolecular interactions (via hydrogen bonds), free energy surfaces for the CHL/PS-MAA/PVPy systems are cons…
Temperature and pressure dependence of phase separation of trans-decahydronaphthalene/polystyrene solution
2004
Abstract The cloud-point temperatures (Tcl’s) of trans-decahydronaphthalene (TD)/polystyrene (PS, Mw=270 kg/mol) solutions were determined by light scattering measurements over a range of temperatures (1–16 °C), pressures (100–900 bar), and compositions (4.2–21.6 vol% polymer). The system phase separates upon cooling and the Tcl was found to increase with the rising pressure for the constant composition. In the absence of special effects this finding indicates positive excess volumes. The special attention was paid to the demixing temperatures as a function of the pressure for the different polymer solutions and the plots in the T-volume fraction plane and P-volume fraction plane. The cloud…