ESCA Studies of Silicone Release Coatings

X-ray photoelectron spectroscopy (XPS or ESCA) has been used to examine the surfaces of silicone release coatings to shed light on phenomena not adequately addressed by our previous contact angle studies. In most cases, the surface composition of the coatings corresponds to pure polydimethylsiloxane. Other components of the coatings, e.g. the emulsifier in the emulsion-based material, are not detected by ESCA. The differences in surface tension between the coatings must be due to other factors, possibly different surface morphologies or low molecular weight constituents that are removed in the high vacuum environment of the ESCA experiment. Delamination has little effect on the surface composition of the silicone coatings but some transfer of silicone to the adhesive occurs in all cases during the release process. The amount transferred increases as the crosslink density of the coating decreases. However, the release force also increases suggesting that bulk effects are more important than surface effects.