Bruce W. Davis

Estimation of surface free energies of polymeric materials

Abstract A new method has been developed for calculating surface free energies of polymeric materials using a simplified solution to the Fowler equation and polarizabilities and diamagnetic susceptibilities for polymer constituent groups. Comparison of this new method with estimates from group parachors, contact angle measurements, or extrapolation of data for melts indicates generally good agreement among the different methods. Discussions are also included on the effect of limited rotation on dipolar interactions and on the proper application of Good and Girifalcos method for estimating surface free energies of solids.

Contact angles for two liquids and a solid in the presence of adsorbed layers

Abstract The Fowler approximation is used to obtain expressions for the surface tension of a pure substance, the interfacial tension between two pure substances, and the case where a slab of intervening material lies below the interface. Numerical solutions are obtained by introducing the 6: 12 interaction potential and a step function approximation for the radial distribution function. Semiquantitative-agreement between predicted and experimental surface and interfacial tensions occurs if the cut-off for the radial distribution function is taken at 0.93 ro. Contact angles are predicted for the H2O/CS2 contact on polyethylene and polytetrafluoroethylene. A hypothetical adsorbed layer is simulated by a slab of CS2 lying below the interface. Contact angles are given as a function of slab thickness.