| Abstrakt: |
The contact angle of water was measured with the Wilhelmy plate method on apolar polymers: soft ethylene−propylene copolymer (EP), rigid polypropylene (PP), and their blends PP/EP (80 wt % PP) and EP/PP (20 wt % PP). Upon liquid displacement, the contact angles of the soft materials, EP and EP/PP, depended on viscoelastic energy dissipation due to solid deformation. This was observed in different situations: wetting and dewetting, liquid displacement due to the relative motion of the plain liquid with respect to the solid, and meniscus relaxation when that motion was stopped. The wetting hysteresis of polymer blends may be understood by considering viscoelastic energy dissipation and the static contact angles. The former depends on the elastic modulus while the latter is determined by the more hydrophobic phase and the less hydrophobic phase, for advancing and receding contact angles, respectively. |
