Polymer-solvent mixture

The industrial process for which this methodology was developed comprised polymerizing a monomer in the presence of a mixed solvent, the catalyst and other Ingredients. Once the batch polymerization is complete, the product requires removal of the solvents to a specified level. The solvents, an aromatic Cy and aliphatic Cy compounds, are removed by a two-step process schematically shown in Figure 1. As shown, the polymer slurry is initially flashed to a lower pressure (Pj ) in the presence of steam and water. The freely available solvent in the polymer-solvent mixture is removed by the shift in thermodynamic equilibrium. Solvent attached to the surface of the polymer particle is removed by the steam. In this first step, 90% of the total solvents are recovered. The remaining solvents are recovered in the second flash, where the effluent is almost all water with very low concentrations of the solvents. 

The characteristic features of phase equilibria in polymer-solvent mixtures will be examined in the present section, the discussion being confined to systems having both phases completely liquid. Equilibria involving a polymer-rich phase in which the polymer is semicrystalline will be the subject of the following section. 

Nanocapsules of biodegradable polymers, such as PLA and PLA copolymers or poly (e-caprolactone), have been prepared by an interfacial polymer deposition mechanism [163-166], An additional component, a water-immiscible oil, is added to the drug-polymer-solvent mixture. A solution of the polymer, the drug, and a water-immiscible oil in a water-miscible solvent such as acetone is added to an external... 

Flory-Huggins Approach. One explanation of blend behavior lies in the thermodynamics of the preceding section, where instead of a polymer-solvent mixture, we now have a polymer-polymer mixture. In these instances, the heat of mixing for polymer pairs (labeled 1 and 2) tends to be endothermic and can be approximated using the solubility parameter. The interaction parameter for a polymer-polymer mixture, Xi2, can be approximated by... 

Figure 8.1. Visual observations of melting, dissolution, and reciystallization of tetrafluoroethylene polymer-solvent mixtures.

Hydrogen bonding in polar polymer-solvent mixtures... 

Nauman and He (2001) considered the modeling of the formation of two-phase morphologies by the spinodal decomposition of the initially homogeneous polymer/polymer or polymer/solvent mixture that was thermally quenched into a two-phase region. Let us outline their modeling approach. 

The reduced volume of the polymer-solvent mixture is calculated using Equation (3C-15). 

You then heat the vial. The polymer/solvent mixture now becomes turbid and looks like milk. You then cool the vial and the polymer/ solvent mixture reverts to a perfectly clear. solution. Explain your observations. 

Computer simulations of the binodal in the phase diagrams of polymer/polymer solvent mixtures have been carried out and show the effect of the various interaction parameters on the shape of the phase diagram. ... 

Under dilatational stresses and in contact with solvents, polymers exhibit a cavitational mode of plasticity called environmental crazing. This phenomenon occurs at small strains in the order of a few percent well below the yield point of the polymer. Environmental crazes are normally observed at the surface of a specimen where the penetrating solvent produces a polymer-solvent mixture. Environmental crazing has been extensively discussed in the literature (see e.g. However, one basic problem in studying this phenomenon arises from the fact that the macroscopic state of the sample at craze initiation may differ considerably from the local one which is, in general, poorly defined. 

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-...

In the case of a polymer-solvent mixture, the phase diagram is highly asymmetric, as depicted in Fig. 9-2, and the critical point is at a low volume concentration of polymer, 0c a where N is the number of segments in the polymer. If a temperature quench,... 

Prediction of the solubihty of gases in binary polymer + solvent mixtures. 

Vergara, A., L. Paduano, and R. Sartorio. 2002. Kirkwood-Buff integrals for polymer solvent mixtures. Preferential solvation and volumetric analysis in aqueous PEG solutions. Phys. Chem. Chem. Phys. 4 4716-4723. 

There is, however, a mass transfer problem of demixing at lower temperatures caused by high viscosities. Concentrated polymer solutions tend to take hours to form two distinct liquid phases. A solution to this problem is the use of the lower critical solution temperature. Because of their thermodynamic nature, all polymer-solvent mixtures tend to form two liquid phases ( LL ) with low viscosities, at higher temperatures (LCST) as depicted in Figure 3. 

Figure 8. Ternary phase diagram of a liquid crystal, polymer, solvent mixture.

Orbey, H., Chen, C.-C., and Bokis, C.P., An extension of cubic equations of state to vapor-liquid equilibria in polymer-solvent mixtures. Fluid Phase Equilibria, 145, 169, 1998. 

Wang, W., Tree, D.A., and High, M.S., A comparison of lattice-fluid models for the calculation of the liquid-liquid equilibria of polymer solutions. Fluid Phase Equilibria, 114, 47-62, 1996. a) Novenario, C.R., Caruthers, J.M., and Chao, K.-C., VLE of polymer+solvent mixtures by the chain-of-rotators EoS, Ind. Eng. Chem. Res., 21, 1033, 1998. b) Saraiva, A., Bogdanic, G., and Fredenslund, Aa., Revision of the GC-Flory EoS for phase equilibria calculations in mixtures with polymers. 2. Prediction of LLE for polymer solutions, Ind. Eng. Chem. Res., 34, 1835, 1995. 

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