Mixtures polymer plus solvent

Shulgin, I. L. and E. Ruckenstein. 2003. Prediction of gas solubility in binary polymer plus solvent mixtures. Polymer. 44, 901. 

Mixed solvents are generally unsatisfactory for use in the determination of polymer molecular weights owing to the likelihood of selective absorption of one of the solvent components by the polymer coil. The excess of polarizabilit f of the polymer particle (polymer plus occluded solvent) is not then equal to the difference between the polarizabilities of the polymer and the solvent mixture. For this reason the refractive increment dn/dc which would be required for calculation of K, or of i7, cannot be assumed to equal the observed change in refractive index of the medium as a whole when polymer is added to it, unless the refractive indexes of the solvent components happen to be the same. The size Vmay, however, be measured in a mixed solvent, since only the dissymmetry ratio is required for this purpose. 

Dynamically, there is an essential difference between this case and the more common problem of one polymer plus one solvent. In the latter problem, near the critical point, backflow is essential, while entanglements are minor but with a molten mixture of chains, the situation is reversed backflow is negligible, and entanglements are essential. 

Organosol. A mixture of polymer and plasticizer used for niolding. Organosol comes from the words organic and solvent. The polymer, which is the organic and is typically PVC, in fine particles is rrtixed as a colloid in plasticizer plus a little solvent. It-all forms goo that can be put in a mold. With a little heat, the solvent evaporates, and the plasticizer and polymer-particle colloid form a gel, the final product. 

The nylons used as modifiers for epoxy adhesives are soluble, semicrystalline copolymers made from conventional nylon monomers.7 These resins can be dissolved in alcohols and other solvents, and they can be melted below their decomposition temperature. A preferred solvent mixture is ethanol plus up to 20% water. A commercial example of an adhesive-grade nylon is Dupont s Zytel 61. Conventional crystalline nylon polymers, such as nylon 6 or nylon 66, would be incompatible with epoxy resins. 

The property levels of cresol free solvent based poly(ester-imide) enamels are inferior to the cresylic products. In Table 3 the cresylic poly(ester-imide) varnish, solved in a mixture of cresol and Solvesso and the cresol free varnish 1, solved in a mixture of diethyleneglycol monomethyl and monoethyl ether plus some small amounts of Solvesso have the same resin composition. The cresylic product is superior. The reason is that the preparation of the cresol free resin was made using diethyleneglycol monomethyl ether as solvent in the synthesis, causing a lower average molecular weight of the polymer. The cresol free po-... 

Today, most polycarbonate is produced by an interfacial adaptation of the reaction in equation 4 (7 ). The bisphenol plus 1-3 raol% monofunctional phenol, which controls molecular weight, is dissolved or slurried in aqueous sodium hydroxide methylene chloride is added as a polymer solvent, a tertiary amine is added as a catalyst, and phosgene gas is dispersed in the rapidly stirred mixture. Additional caustic solution is added as needed to maintain basicity. The growing polymer dissolves in the methylene chloride, and the phenolic content of the aqueous phase diminishes. 

The decrease is due to the incompatibility existing between polymer A and polymer B. The quantity A[t7]b = ([t ] B [t ] BA)/[t ]B similarly gives the decrease of the intrinsic viscosity of polymer B due to the presence of polymer A in the solvent. The constant quantity of the polymer A or B in the mixture, solvent plus polymer, is always the same (typically 0.125 X10 g/cm ). Then the quantity A[i7]ab given by Equation (4.4) expresses a measure of the incompatibility existing between polymer A and polymer B. A high value of AjtjjAB for a polymer pair indicates a high value of incompatibility and vice versa. 

Other ingredients, such as stabilizers, fillers, colorants, surfactants, and possibly blowing agents or gelling agents are also present. The polymer particles do not dissolve in the liquids but remain dispersed until the mixture is heated. Fusion (plus loss of solvent for the organosols) then yields the final plastic object. 

Despite the fact that these solutions represent binary systems, at least three Hory-Huggins interaction parameters are involved in their modeling, like with ternary mixtures. Because of the necessity to account for the interaction of the solvent with monomer A and with monomer B, plus the interaction between the polymers A and B, one should expect the need for a minimum of two additional parameters. Experimental data obtained for solutions of a given copolymer of the type A-ran-B with a constant fraction / of B monomers can be modeled [25] by means of (32), with one set of a, v, and parameters. For predictive purposes, it would of course be interesting to find out how these parameters for the copolymer solution (subscripts AB) relate to the parameters for the solutions of the corresponding homopolymers in the same solvent (subscripts A and B, respectively) at the same temperature. 

Release systems based on this condensation cure chemistry are commonly sold as two-part packages. One (A) is a high-solids solution of the silanol-terminated high viscosity polymer (commonly called a gum) plus the methylhy-drogen crosslinker. The second part (B) is a solution of the tin soap catalyst. Further dilution of the A and B mixture is then done with more solvent to achieve an approximate 5-10% solids content the bath is then adequately coat-able by techniques such as reverse roll, rotogravure, metering rod, or doctor blade. 

CPC and spinodal curve touch each other and share a common tangent as required by thermodynamics. Only for mixtures of exactly two chemical species, e.g. pure solvent plus completely homodisperse polyethylene, is the critical point situated at a common extremum of both the spinodal and binodal curve. In the case of UCST behaviour the extremum is a maximum if it is a minimum, it is called a lower critical solution temperature (LCST). In polydisperse polymer solutions, even for polymers characterized by a narrow MWD, the critical point moves appreciably away from the extremum of the CPC towards the polymer rich side of the phase diagram as is shown in Figure 1. 

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