Polymer solution temperature dependence

Simha, R., and Chan, F. S., Corresponding state relations for the Newtonian viscosity of concentrated polymer solutions temperature dependence, J. Phys. Chem., 75, 256-267 (1971). 

The melting point Tm is computed by solving this equation iteratively. It is often convenient to use Ec/(kBTm) as our unit of (inverse) temperature. The phase diagram of the polymer solution then depends on the molecular parameters r, q, B/Ec, and Ep/Ec, the composition parameters n and 2, and on the temperature parameter Ec/(kBTm). 

Let s designate a force such as stirring or spreading a shear force. By shearing we mean forcing the molecules to slide past each other. No matter how hard we stir a pot of water or a jar of honey at constant temperature, the viscosity remains the same because both are Newtonian liquids. But what happens when we stir some polymer solutions It depends. Not all of the examples we discuss below are true solutions. So we ll use the broader term fluid. ... 

The solubility of polymers is highly solvent and solution temperature dependent [76], As a result, some of the early pioneering work on plastics recycling examined selective dissolution of polymers as a means to separate different plastics from mixtures [2, 75, 93-95]. Various plastic-solvent combinations are shown here ... 

On account of the dual retention mechanism, the shapes of experimental retention diagrams, for a given polymer-solute system, depend directly on the sm face to volume ratio of the stationary phase at temperatures above Tg. In the equilibrium region III the net retention volume is given, according to eqn (4.11), by the sum of the volumes for the two contributions [161] ... 

Harrah LA. Excimer formation in vinyl polymers. I. Temperature dependence in fluid solution. J. Chem. Phys. 1972 56 385-389. 

Fig. 9. Pressure and polymer solution composition dependences of the enthalpy of the mixing, AH, for the TD/PS polymer solutions at the indicated temperature (the inserted figure shows pressure dependences of the enthalpy of the mixing, AH, for the TD/PS polymer solutions with fixed composition and temperature).

Fig. 10. Temperature and polymer solution composition dependences of the volume change of the mixing,, for the TD/PS polymer solutions under the indicated pressures.

Vitrification, whereby the polymer chains are immobilized when the glass transition temperatme is passed. The glass transition temperature of a polymer solution is dependent on the type of polymer and solvent, as well as the eoneentration of the polymer [11]. 

Polymer solution viscosity is dependent on the concentration of the solvent, the molecular weight of the polymer, the polymer composition, the solvent composition, and the temperature. More extensive information on the properties of polymer solutions may be found ia refereaces 9 and 54—56. 

The heated polymer solution emerges as filaments from the spinneret into a column of warm air. Instantaneous loss of solvent from the surface of the filament causes a soHd skin to form over the stiU-Hquid interior. As the filament is heated by the warm air, more solvent evaporates. More than 80% of the solvent can be removed during a brief residence time of less than 1 s in the hot air column. The air column or cabinet height is 2—8 m, depending on the extent of drying required and the extmsion speed. The air flow may be concurrent or countercurrent to the direction of fiber movement. The fiber properties are contingent on the solvent-removal rate, and precise air flow and temperature control are necessary. 

Concentration and Molecular Weight Effects. The viscosity of aqueous solutions of poly(ethylene oxide) depends on the concentration of the polymer solute, the molecular weight, the solution temperature, concentration of dissolved inorganic salts, and the shear rate. Viscosity increases with concentration and this dependence becomes more pronounced with increasing molecular weight. This combined effect is shown in Figure 3, in which solution viscosity is presented as a function of concentration for various molecular weight polymers. 

In order to observe any temperature dependence in transient flow degradation, it would be necessary to prolong considerably the effective residence time of the polymer coil. This can be accomplished either by recirculating the solution or by using an oscillatory flow equipment as described in Sect. 4.1 (Figs. 23 and 24). 

Cationic polymerization of cyclic acetals generally involves equilibrium between monomer and polymer. The equilibrium nature of the cationic polymerization of 2 was ascertained by depolymerization experiments Methylene chloride solutions of the polymer ([P]0 = 1.76 and 1.71 base-mol/1) containing a catalytic amount of boron trifluoride etherate were allowed to stand for several days at 0 °C to give 2 which was in equilibrium with its polymer. The equilibrium concentrations ([M]e = 0.47 and 0.46 mol/1) were in excellent agreement with that found in the polymerization experiments under the same conditions. The thermodynamic parameters for the polymerization of 1 were evaluated from the temperature dependence of the equilibrium monomer concentrations between -20 and 30 °C. 

This stipulation of the interaction parameter to be equal to 0.5 at the theta temperature is found to hold with values of Xh and Xs equal to 0.5 - x < 2.7 x lO-s, and this value tends to decrease with increasing temperature. The values of = 308.6 K were found from the temperature dependence of the interaction parameter for gelatin B. Naturally, determination of the correct theta temperature of a chosen polymer/solvent system has a great physic-chemical importance for polymer solutions thermodynamically. It is quite well known that the second viiial coefficient can also be evaluated from osmometry and light scattering measurements which consequently exhibits temperature dependence, finally yielding the theta temperature for the system under study. However, the evaluation of second virial... 

The solution to this problem has been to isolate the lactide and to polymerize this directly using a tin(ii) 2-(ethyl)hexanoate catalyst at temperatures between 140 and 160 °C. By controlling the amounts of water and lactic acid in the polymerization reactor the molecular weight of the polymer can be controlled. Since lactic acid exists as d and L-optical isomers, three lactides are produced, d, l and meso (Scheme 6.11). The properties of the final polymer do not depend simply on the molecular weight but vary significantly with the optical ratios of the lactides used. In order to get specific polymers for medical use the crude lactide mix is extensively recrystallized, to remove the meso isomer leaving the required D, L mix. This recrystallization process results in considerable waste, with only a small fraction of the lactide produced being used in the final polymerization step. Hence PLA has been too costly to use as a commodity polymer. 

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