INTERACTION OF SUPERCRITICAL CARBON-DIOXIDE WITH POLYMERS .1. CRYSTALLINE POLYMERS

Supercritical fluid (SCF) technology involving carbon dioxide is recen tly receiving wide attention due to its vast potential application in various fields such as cleaning, extraction, synthesis, etc., in addit ion to its environmental benefits. To fully exploit the use of SCFs in new technologies, it is important to understand how SCFs interact wit h materials. To this end, we have undertaken a systematic study involv ing a wide pressure and temperature range to investigate the interacti on of supercritical carbon dioxide (SC CO2) with nine different crysta lline polymers, namely, substituted anti unsubstituted polyethylene (f our varieties), polypropylene, nylon 66, poly(ethylene terephthalate), poly(oxymethylene), and poly(vinylidine fluoride). Critical factors s uch as changes in appearance and weight, temperature, pressure and tim e of the supercritical fluid treatment, and dimension of samples have been observed. The influence of SC CO2 on the thermal properties of tr eated polymers has been investigated through TGA analysis. Further, ch anges in the mechanical properties such as yield strength, ultimate el ongation, and modulus of elasticity of the investigated crystalline po lymers were also observed. A discussion has been included to show the possible implications of the observed changes in realizing various app lications. (C) 1996 John Wiley & Sons, Inc.