Measurement of interfacial tension in PS/LDPE melts saturated with supercritical C[O.sub.2]

The effect of supercritical carbon dioxide (scC[O.sub.2]) on the interfacial tension between a polymer melt pair--polystyrene (PS) and low density polyethylene (LDPE)--was studied using the pendant drop method at temperatures varying from 200 to 240°C and C[O.sub.2] pressures up to 18 MPa. The LDPE melt was prepared in a high pressure optical cell and the PS pendant drop was injected into the LDPE melt with a special high pressure syringe. For measurements with scC[O.sub.2], the optical cell was first pressurized with scC[O.sub.2] and measurements were taken after the saturation of scC[O.sub.2], into both polymer melts. Excellent agreement was found with literature data for the same system without using scC[O.sub.2]. For the polymer pair saturated with scC[O.sub.2], it was found that the interfacial tension decreases significantly with increasing C[O.sub.2] pressure and appears to level off at higher C[O.sub.2] pressures.