Carbon dioxide with Polystyrene (PS) (IUPAC SDS Volume 70)
Evaluator
Yuri P. Yampol'skii A. V. Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences
Evaluation
Nine experimental studies are available for the solubility of carbon dioxide in PS. In several papers this system was studied in the range of glassy state of this polymer and at pressures as high as 7.0 MPa.3,4,6-9 Newitt et a1.1 and Durrill2 have studied the solubility at higher temperatures and pressures. Chiou, Maeda, and Paul5 have investigated sorption in plasticized PS.

Different samples of PS having molecular mass in the range 36 000-850 000 were studied in the range of temperature 293-393 K. Up to 333 K sorption isotherms are concave to the pressure axis, i.e., agree with the dual mode sorption model, above this temperature they are linear possibly due to the plasticization effect exerted by carbon dioxide on PS.

A summary of the dual mode sorption parameters as well as the apparent solubility coefficients S are given in Table 1.

The parameters kd and b decrease with temperature but do not form an overall smooth dependence. Accordingly, is is not included into this critical evaluation and, for the temperatures 293-313 K, the results of Sada et al.7 and, for the range 313-333 K, the results of Carfagna et al.6 should be recommended.

The values of C'H and S found by different authors4,6,1,9 are in good agreement and form, within experimental scatter, a smooth temperature dependence ( Figures 16 and 17 ). The results of Vieth et al.3 reveal a deflection from these and were excluded from the group of recommended values.

Temperature dependence of C'H intersects the horizontal axle at about 360 K, i.e., somewhat lower than accepted glass transition temperature of PS (about 373 K).

Temperature dependence of the apparent solubility coefficient can be given by time equation

log(S/cm3(STP) cm-3 atm-1) = -2.840 + 970.0/(T/K).

Enthalpy of sorption in equal to -18.6 kJ/mol.

The interval of higher pressure has been investigated by Wissinger and Paulaitis.8 They found nearly linear sorption isotherms, probably, owing to the plasticization effects. The solubilities found in Ref. 6 and 8 for 3.0 MPa, where the presaure ranges of two works overlap, are in good agreement. So for higher pressure the renults of Ref. 8 may be recommended.

All the results considered shove concern high molecular mass PS (MM about 105). Toi and Paul4 studied the effects of the molecular mass of PS on the solubility and the parameters of the dual mode sorption isotherms. The increase in molecular mass from 3 600 to 850 000 results in the increase in the solubility at any given pressure as well as in the values of C'H, while two other parameters remain intact.

The solubility in PS stretched or biaxially oriented was studied by Vieth et al.3 and Carfagna et a1.6 It was shown that the deformation tends to decrease the solubility. Meanwhile, no quantitative recommendation can be made basing on the results of thaee papers.

The range of rubbery state of PS was investigated touch less thoroughly.1,2 The results of Newitt and Weale1 and of Dyrrill2 do not agree with each other. The results of Ref. 2 may be preferred at least tentatively. Further studies are needed to resolve this range of conditions.

Table 1. The dual mode sorption parameters at different temperatures
C $T$ ($\pu{K}$) D $S$ ($\pu{cm3(g) cm-3(s) atm-1}$) D $k_{\rm{H}}$ D $C_{\rm{H}}^{\prime}$ ($\pu{cm3/cm3}$) D $b$ ($\pu{atm-1}$)
293.0 3.19 8.01 x 10-1 13.0 1.84 x 10-1
303.0 2.19 7.13 x 10-1 11.0 1.34 x 10-1
308.0 2.2 5.35 x 10-1 8.6 1.94 x 10-1
308.0 1.97 5.0 x 10-1 9.2 1.6 x 10-1
313.0 1.4 5.86 x 10-1 8.8 9.2 x 10-2
313.0 1.96 8.0 x 10-1 8.3 1.4 x 10-1
323.0 1.6 7.0 x 10-1 6.0 1.5 x 10-1
333.0 1.21 6.6 x 10-1 5.0 1.1 x 10-1

Figures
Solubility graph
Solubility graph
Sources:

1 Newitt, D. M.; Weale, K. E.; J. Chem. Soc.; 1541-1549 (1948).
2 Durrill, P. L.; Ph.D. Dissertation, Virginia Polytech. Inst. (1965).
3 Vieth, W. R.; Tam, P. M; Michaels, A. S.; J. Colloid Interface Sci. 22, 360 (1966).
6 Carfagna, C.; Nicodemo, L.; Nicolais, L.; Campanile, G.; J. Polym. Sci. B: Polym. Phys. 24, 1805 (1986).
7 Sada, E.; Kumazawa, H.; Yakushiji, H.; Bamba, Y.; Sakata, K.; Wang, S. -T.; Ind. Eng. Chem. Res. 26, 433-438 (1987).
5 Chiou, J. S.; Maeda, Y.; Paul, D. R.; J. Appl. Polym. Sci. 30, 4019 (1985).
4 Toi, K.; Paul, D. R.; Macromolecules 15, 1104 (1982).
9 Raymond, P. C.; Paul, D. R.; J. Polym. Sci. B: Polym. Phys. 28, 2079-2102 (1990).
8 Wissinger, R. G.; Paulaitis, M. E.; J. Polym. Sci. B: Polym. Phys. 25, 2497-2510 (1987).