Wettability characteristics of treated aluminum surfaces

The surface free energy of aluminum surfaces treated with silicon compounds was studied by wetting procedures. The polar component gamma(s)P was determined from contact angle measurements. Two methods were applied: Kaelble's method and the newly developed MSSDC method (minimizing the sum of the square of the differences between the cosines of measured and calculated angles). It has been shown that the MSSDC method is superior to Kaelble's method because it gives proper results without omitting any arbitrary data. Two kinds of treatments were compared, the silane coupling agent treatment and the sol-gel treatment. The higher gamma(s)P values of the silane coupling agent treated surfaces have been attributed to abundant -OCH3 and -OC2H5 groups on these surfaces in contrast to dominant siloxane networks on the sol-gel treated surfaces. This is the reason why the former surfaces bring about strong affinities with printing inks to cause undesired stains in non-imaged areas. (C) 1998 Elsevier Science B.V. All rights reserved.