POLYMER DRYING .1. EFFECT OF HISTORY ON THE KINETICS OF EVAPORATION FROM POLY(STYRENE-CO-DIVINYLBENZENE) LIQUID-SYSTEMS IN THE RUBBERY AND GLASSY STATES

In these time studies of evaporation from liquid-saturated microporous composite film samples, comprised of poly(styrene-co-divinylbenezene) particles enmeshed in poly(tetrafluoroethylene) microfibers, the samp les were preswelled to saturation in a good solvent, such as toluene, which was then replaced via solvent exchange in excess test liquid bef ore the start of the time study that monitored the residual weight (W( t)) of sorbed liquid to virtual dryness. The patterns of change with t ime (i.e., W(t) vs. t and Log W(t) vs. t) obtained thereby were compar ed with the corresponding time studies already reported for evaporatio n from equivalent polystyrene-liquid (PS-L) systems that did not have a history of preswelling in a better solvent. These comparisons show t hat the history of the sample in its liquid-saturated gel state can af fect markedly the kinetics of desorption from the PS-L system in its g lassy state, and also during the interval of transition from the rubbe ry state to the glassy state, as discussed in the text. (C) 1994 John Wiley & Sons, Inc.