The wettabilities of Al(2)O(3)/nylon 1010 (Al(2)O(3)/PA1010) composite, polysiloxane/steel T8 (polysiloxane/T8) composite, polyethylene, nylon 1010, nylon 6, polystyrene, steel T8 (a high carbon steel with 0.75-0.84% carbon), steel 45 (a medium carbon steel with 0.42-0.50% carbon), and Al(2)O(3) surfaces were tested and analyzed. The contact angles of water and formamide on their surfaces were measured. For composite surfaces formed by dispersing particles in a matrix, an equation relating the contact angle on the composite surface with the contact angles on component materials and the volume fraction of the dispersed phase has been derived. Using this equation, the contact angle on the composite surface can be easily calculated from the contact angles on component materials and the volume fraction of the dispersed phase. For the composite surfaces with Al(2)O(3) particles dispersed in PA1010 matrix, the measured values of the contact angles are in agreement with the values calculated by the equation. It was found that the size of Al(2)O(3) particles had almost no influence on the contact angle on Al(2)O(3)/PA1010 composite surface when the content of Al(2)O(3) particles was in a certain range. However, the hydrophobicity of polysiloxane/T8 composite surface is considerably enhanced in comparison to that of steel T8. The wettability of rough surfaces of steel, Al(2)O(3), and polymers used in the experiment was obviously different from that of their smooth surfaces, and the change in the contact angle on rough surfaces depends on the contact angle on the smooth surfaces of these materials. The greater is the difference between the value for the smooth surface contact angle and 90 degrees, the greater is the influence of surface roughness on contact angles. (c) Koninklijke Brill NV, Leiden, 2008