EHD FILM FORMATION AND STARVATION OF OIL-IN-WATER EMULSIONS

The elastohydrodynamic film-forming properties of oil-in-water emulsions in rolling point contacts have been investigated using a combination of ultrathin film interferometry and short duration TV microscopy. It has been shown that at slow rolling speeds, all the o/w emulsions tested formed EHD films comparable to those of their water-free components. Above a certain critical rolling speed, which depended upon the emulsion composition, the film thickness started to decrease. This was due to EHD starvation, and the film thickness/inlet oil meniscus relationships developed for starved oil systems were found to apply to emulsion starvation. At high rolling speeds, the EHD film thickness did not collapse to zero, but instead leveled off at a low value, typically 10 to 30 nm, which persisted to the highest rolling speeds attained.