Zisman rule

Zisman s Rule. Having treated a surface, wettability can be characterised by measuring the contact angle for each member of the alkane series. The curve cos E = /(7n) (see Fig. 1.7) is used to define a critical surface tension qc ... 

This rule, due to Zisman, is a useful way of characterising a surface treatment. It can be used to predict wettability by simple liquids, subject only to van der Waals forces, but becomes inaccurate for polar liquids. 

As a next step, Zisman combines Dupre s rule with Eqs. 6.12 and 6.17 to give... 

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