Polymer supercritical

A number of theoretical models have been proposed to describe the phase behavior of polymer—supercritical fluid systems, eg, the SAET and LEHB equations of state, and mean-field lattice gas models (67—69). Many examples of polymer—supercritical fluid systems are discussed ia the Hterature (1,3). 

Gas AntisolventRecrystallizations. A limitation to the RESS process can be the low solubihty in the supercritical fluid. This is especially evident in polymer—supercritical fluid systems. In a novel process, sometimes termed gas antisolvent (GAS), a compressed fluid such as CO2 can be rapidly added to a solution of a crystalline soHd dissolved in an organic solvent (114). Carbon dioxide and most organic solvents exhibit full miscibility, whereas in this case the soHd solutes had limited solubihty in CO2. Thus, CO2 acts as an antisolvent to precipitate soHd crystals. Using C02 s adjustable solvent strength, the particle size and size distribution of final crystals may be finely controlled. Examples of GAS studies include the formation of monodisperse particles (<1 fiva) of a difficult-to-comminute explosive (114) recrystallization of -carotene and acetaminophen (86) salt nucleation and growth in supercritical water (115) and a study of the molecular thermodynamics of the GAS crystallization process (21). 

SFE has been used extensively in the analysis of solid polymers. Supercritical fluid extraction of liquid samples is undertaken less widely because dissolution or entrainment of the matrix can occur. As illustrated elsewhere SFE has also been applied for the analysis of liquid poly(alkylene glycol) (PAG) lubricants and sorbitan ester formulations [370]. The analysis of PAG additives (antioxidants, biocides and anticorrosion, antiwear and antifoaming agents) is hindered by the presence of the low molecular weight PAG matrix (liquid) and therefore a method for the selective separation of additives from PAG is required. The PAG... 

Polymer-supercritical fluid systems, phase behavior of, 24 11... 

Optimizing solvents and solvent mixtures can be done empirically or through modeling. An example of the latter involves a single Sanchez-Lacombe lattice fluid equation of state, used to model both phases for a polymer-supercritical fluid-cosolvent system. This method works well over a wide pressure range both volumetric and phase equilibrium properties for a cross-linked poly(dimethyl siloxane) phase in contact with CO2 modified by a number of cosolvents (West et al., 1998). 

The phase behaviour of binary polymer - supercritical fluid systems can be modelled with an equation of state model. In general, non-cubic equations of state are used, mainly from the PHCT and SAFT families. Lattice-fluid equations of state are also commonly used for the... 

A Statistical-Mechanics based Lattice-Model Equation of state (EOS) for modelling the phase behaviour of polymer-supercritical fluid mixtures is presented. The EOS can reproduce qualitatively all experimental trends observed, using a single, adjustable mixture parameter and in this aspect is better than classical cubic EOS. Simple mixtures of small molecules can also be quantitatively modelled, in most cases, with the use of a single, temperature independent adjustable parameter. 

Representation of Polymer-Solvent and Polymer-Supercritical Fluid VLE and LLE with the EOS Models... 

Shim, J.J. and Johnston, K.P., Molecular thermodynamics of solute-polymer-supercritical fluids, AIChE J., 37, 607-616, 1991. 

Pesticides, 161,165 Peter, S., 10 Peters, C. J., 77 Peterson, R. C., 336 Petsche, 1. B., 105 pH effect, 180-181 Pharmaceuticals, 304-307, 340, 347 Phase behavior, 27-45 binary mixtures, 31-45 elassifieation scheme, 29 polymer-supercritical fluid, 61-71 semicrystalline polymers, 199-201 solid-supercritical fluid, 45-61 ternary mixtures, 71-84... 

Liau, I. S., and M. A. McHugh. 1985. High pressure solid polymer-supercritical fluid phase behavior. In Supercritical Fluid Technology, ed. J. M. L. Penninger, M. Radosz, M. A. McHugh, and V. J. Krukonis, 415. New York Elsevier. 

HA4 Haschets, C.W. and Shine, A.D., Phase behavior of polymer-supercritical chlorodifluoro-methane solutions, Macrowo/ecM/es, 26, 5052, 1993. 

Some new cosolvent effects will be also described particularly of polymer-supercritical CO2 mixtures. 

Polymer supercritical-fluid systems show complex phase behavior (for a general overview see also [80]). Polymer solubihty in these systems depends on (apart from temperature, pressure, and concentration) the chemical nature, molecular weight, and molecular-weight distribution of the polymer and on the comonomer composition in the case of copolymers. 

The use of supercritical CO2 can be beneficial in reactive blending also. Here, where a monomer polymerizes in a host polymer, supercritical CO2 improves the infusion of reagents (monomer and initiator) into the host polymer, after which a polymerization reaction of the monomer is carried out For this process... 

Kalospiros, N.S. and M.E. Paulaitis, Molecular thermodynamic model for solvent-induced glass transitions in polymer supercritical-fluid systems. Chemical Engineering Science, 1994. 49(5) p. 659-668. 

Haschets, C.W. and A.D. Shine, Phases behavior of polymer supercritical chlorodifluoromethane solutions. Macromolecules, 1993. 26(19) p. 5052-5060. 

Gromov, D. G., de Pablo, J. J., Luna-Barcenas, G., Sanchez, I. C. and Johnston, K. P. (1998) Simulation of phase equilibria for polymer-supercritical solvent mixtures, J. Chem. Phys. 108,4647. 

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