Thermal resistance interfacial, condensation

More recently, similar polysulfonates, eg, (61) and (62), prepared by conventional interfacial condensation using water-chloroform as an interface, alkali as an acid acceptor, and cetyltrimethylammonium bromide [57-09-0] as an emulsifier have thoroughly been studied (195-206). In general, the polymers possess good solubility in common solvents, good acid and alkali resistance, thermal stabilities of up to 355°C, and tensile strength of up to 20 MPa (199). 

The idea that agrees best with experiments is that initially tiny drops form at nuclei sites, at depressions in the condensation surface or on the remnants of liquids. Their growth rate is determined by the resistance to thermal conduction in the drops and also partly by the thermal conduction resistances at the phase interface with the vapour. The growth rate is therefore only dependent on the specific drop radius and the driving temperature difference. This has also been confirmed by experiment [4.24], The main reasons behind the lack of success in developing an explicit theory are that the nucleation site density is unknown, and it is difficult to predict the radius of the rolling drops, as this depends on the purity and smoothness of the condensation surface as well as the interfacial tension. 

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