Simultaneous measurement of the solubility of nitrogen and carbon dioxide in polystyrene and of the associated polymer swelling

New experimental results for the solubility of nitrogen and carbon dioxide in polystyrene are reported, accompanied by data on the change in volume of the polymer caused by the sorption process. The two phenomena were measure d simultaneously with a combined technique, in which the quantity of penetr ating fluid introduced into the system was evaluated by pressure-decay meas urements in a calibrated volume, whereas a vibrating-wire force sensor was employed for weighing the polymer sample during sorption inside of the high -pressure equilibrium cell. The use of the two techniques was necessary bec ause the effects of Swelling and solubility could not be decoupled in a sin gle gravimetric or pressure-decay measurement. The sorption of nitrogen in polystyrene was studied along three isotherms from 313 to 353 K at pressure s up to 70 MPa. The sorption of carbon dioxide was measured along four isot herms from 338 to 402 K up to 45 MPa. The results are compared with values from the literature when possible, although our data extend significantly t he pressure ranges of the latter. The uncertainties affecting our measureme nts with nitrogen are I mg of N-2/g of polystyrene in solubility and 0.1% o f the volume of the polymer. For carbon dioxide, the uncertainties are 5 mg of N-2/g of polystyrene and 0.5% respectively, carbon dioxide being about 1 order of magnitude more soluble than nitrogen. (C) 2001 John Wiley & Sons , Inc.