Measurement of interfacial tension in PS/LDPE melts saturated with supercritical CO 2

The effect of supercritical carbon dioxide (scCO 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 CO 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 scCO 2 , the optical cell was first pressurized with scCO 2 and measurements were taken after the saturation of scCO 2 into both polymer melts. Excellent agreement was found with literature data for the same system without using scCO 2 . For the polymer pair saturated with scCO 2 , it was found that the interfacial tension decreases significantly with increasing CO 2 pressure and appears to level off at higher CO 2 pressures.