Film forming processing surface-oriented phase

Gibbs equation. The adsorption process involves the transport of molecules from the bulk solution to the interface, where they form a specially oriented monomolecular layer according to the nature of the two phases. When a Gibbs monolayer forms, it does not necessarily mean that the molecules are touching each other in this monolayer. Instead, if the anchoring from the sub-phase molecules is weak, the molecules may move freely in the two-dimensional interfacial area. Thus, the physically measurable monolayer area is sometimes much larger than the close-packed area where all the molecules touch each other. When any monolayer is fairly well populated with adsorbed molecules, it exerts a lateral spreading (film) pressure, it, which is equal to the depression of the surface tension (see Section 5.5.2). 

It is generally assumed that surface-active molecules accumulate on the surface and are oriented such that the hydrophobic part containing the hydrocarbon chain extends into the plastic, and the hydrophilic part points outwards there it is able to absorb water on the surface. The phase boundary angle between water and plastic is reduced by the surface active antistatic agents thus allowing the absorbed water to be uniformly distributed on the plastic surface. A water film forms on the surface thus increasing the conductivity by means of an ion conduction process. This also explains why surface conductivity, and hence the antistatic action, are found to increase with increasing atmospheric humidity. 

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