Toluene-polystyrene system

Figure 5-3 Test of predictive capabilities of proposed free-volume model using data for the toluene polystyrene system. Only data points represented by solid symbols were used to obtain free-volume parameters (73).

Fig. 13. Concentration dependence of the self-diffusion coefficient and the thermodynamic factor Q for the toluene-polystyrene system at 110°C and for the o-xylene-polyethylene system at 150°C. Q = (l a>A)(d In a /d In coa- From Ref. 45.

Except for supercritical extraction conditions, hydrostatic pressure effects are typically of negligible importance for simple solvent vapors diffusing in polymers, since the saturation vapor pressure is low, <101.3 kPa (1 atm), in most applications. The predictive power of the approach is indicated by the results for the mutual diffusion coefficient of toluene in a toluene-polystyrene system (Fig. 14) (35). 

Fig. 14. Dependence of diffusivity on mass fraction for the toluene-polystyrene system.

Solution We approximate the styrene-polystyrene system by using a toluene-polystyrene system. For this, the viseosity ean be estimated by... 

This process has been illustrated by Duda et al. for a variety of polymers [59] and Figine 13.12 shows the predictive abilities of their theory for the toluene-polystyrene system. Parameter values used are listed in Table 13.1. The results obtained are excellent. These authors also note that the diffusion coefficient given by Eq. (13.6.11) is insensitive to polymer molecular weight, and there is, therefore, no influence of polydispersity. Furthermore, for semicrystalline polymers above the glass transition temperature, the polymer may be considered to be made up of two phases—one of which has a zero diffusivity [51]. Thus, if the volume fiaction of the crystalline phase is 4>, the effective diffusivity of the polymer is D(j). Finally, Kulkami and Mashelkar [63] have proposed an altered fi-ee-volume-state model that seeks to provide a unified... 

Figure 13.12 Test of predictive capabilities of free-volume theory using data for the toluene-polystyrene system. Only data points represented by solid symbols were used to obtain free-volume parameters. (From Duda, J. L., J. S. Vrentas, S. T. Ju, and H. T. Liu Prediction of Diffusion Coefficients for Polymer-Solvent Systems, AIChE J., vol. 28, pp. 279-285. Reproduced with the permission of the American Institute of Chemical Engineers Cop3right 1982 AIChE. All rights reserved.)...

Seckner A.J., McClellan A.K., McHugh M.A., High-Pressure Solution Behavior of the Polystyrene-Toluene-Ethane System AIChE J. 1988, 34(1), 9-16... 

Seckner, A. J. McClellan, A. K. McHugh, M. A., "High-Pressure Solution Behavior of the Polystyrene-Toluene- Ethane System," AlChE J., 34, 9 (1988). 

Lundberg. Bull s data at T = 298.15 K have been used for the activity of water in this system." Starkweather has determined the activity of water in the concentration range 0 volume fraction as ai = 12 1, the expression that was used in our calculations. The molecular weight and the partial specific volume of collagen were taken from ref 41. The results of the calculations are presented in Figures IB, 2B, and 3B. In contrast to the toluene + polystyrene mixture, the solvent (water) is in deficit around a central water molecule but in excess around a protein molecule. 

The potential of this separation technique is demonstrated by Seckner, McClellan, and McHugh (1988) with the polystyrene-toluene-ethane system shown in figure 9.51. Without any ethane, the LCEP for the polystyrene-... 

Figure 9.52 Ternary behavior of the polystyrene-toluene-ethane system (Seckner, McClellan, and McHugh, 1988).

Scott, R. L., and P. B. van Konynenburg. 1970. Static properties of solutions van der Waals and related models for hydrocarbon mixtures. Discuss. Faraday Soc. 49 87. Seckner, A. J., A. K. McClellan, and M. A. McHugh. 1988. High-pressure solution behavior of the polystyrene-toluene-ethane system. AIChE J. 34 9-16. 

Figure 4.4.15. Experimental data of the system toluene + polystyrene, = 1380 g/mol, at 323.15K, isopiestic vapor pressure/sorption measurement (fiill circles), VPO at higher concentrations (gray circles), data from authors own work.

Subsequent measurements of swelling ratios were carried out in a toluene-methanol mixture (75/25 wt%). By making use of the cycle rank values determined above, values of the interaction parameter for the polystyrene-toluene-methanol system were calculated at different temperatures by means of equation (156). Least-squares analysis of the data gave equation (163) for the dependences of x on V2 and T,... 

Fig. 6. Specific viscosity, r sp, as a function of the product c- [q] for narrowly distributed polystyrene in toluene (good solvent) (A) and frans-decalin (poor solvent) ( ) at 25 °C. Experimental data for the polystyrene/toluene system at 30 °C (taken from [65]) are represented by (O). 

One of the earliest published studies on extraction in twin-screw extruders was conducted by Todd (1974). In this work devolatilization was conducted under vacuum using two different polymeric systems, polystyrene in one and polyethylene in the other. In the case of polystyrene, styrene was not used as the volatUe component so as to avoid problems associated with further polymerization or depolymerization instead, use was made of mixtures of thiophene and toluene or ethylbenzene. Todd found good agreement between the measured exit concentrations of the volatile component and the predicted values using Pe = 40 in the solution to Eq. (38) (see Fig. 15). The value of 5 in Eq. (39) was not reported and it is not known whether a value was chosen to provide a fit with the data or whether it was known a priori. In any event, what is clear is that the exit concentration varies with IVwhich suggests that mass transfer is occur-... 

The solvent mobility in atactic polystyrene-toluene solutions has been studied as a function of temperature using NMR. The local reorientation of the solvent was studied using deuterium NMR relaxation times on the deuterated solvent. Longer range motions were also probed using the pulsed-gradient spin-echo NMR method for the measurement of diffusion coefficients on the protonated solvent. The measurements were taken above and below the gel transition temperatures reported by Tan et al. (Macromolecules, 1983. 16, 28). It was found that both the relaxation time measurements and the diffusion coefficients of the solvent varied smoothly through the reported transition temperature. Consequently, it appears that in this system, the solvent dynamics are unaffected by gel formation. This result is similar to that found in other chemically crossed-linked systems. 

BLUM AND naNAGARA Atactic Polystyrene-Toluene Systems... 

The high-pressure phase behavior of polymer-solvent-supercritical carbon dioxide systems was investigated experimentally The polymers used were poly(methyl methacrylate), polystyrene, polybutadiene, and poly(vinyl ethyl ether) at concentrations ranging from 5 to 10% in mixtures with toluene or tetrahydrofuran. The experiments were conducted for temperatures from 25 to 70°C and pressures up to 2200 psi in a high-pressure cell (Kiamos and Donohue, 1994). 

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