Surface characterization method adhesive bonding

Aspects of Adhesive Bonding and Applicable Surface Characterization Methods... 

In deciding which surface chemistry tools to use for the broad area of adhesion and for adhesive bonding in particular, a number of aspects must be considered. More often than not, a combination of instruments must be used to take advantage of the unique information provided by each method. Table 1 shows some of the important aspects of adhesive bonding and some of the characterization methods... 

Ion beams provide useful information either as a diagnostic tool or as a precision etching method in. adhesive bonding research. The combination of SIMS with complementary methods such as ISS or AF.S provides a powerful tool for elemental end limited structural characterization of metals, alloys and adhesives. The results shown here indicate that surface chemistry (and interface chemistry) can be decidedly different from bulk chemistry. Often it is this chemistry which governs the quality and durability of an adhesive bond. These same surface techniques also allow an analysis of the locus of failure of bonded materials which fail in service or test. 

One important influence in the formation of a good adhesive bond is surface or interfacial chemistry. In the broader sense, in which two substances are held together by interfacial forces, adhesion is of importance in many technologies such as in thin films and semiconductors. It is the purpose of this paper to discuss ion beam methods of surface characterization applicable to the broad area of adhesion with emphasis on adhesive bonding. 

Earlier we considered the regularities of the effect of simfactants on the oligomer surface tension. The properties of adhesive-bonded joints are also determined by the character and the magnitude of the interaction at the adhesive-substrate interface, which to a greater extent is characterized by the magnitude of the interphase tension [82]. Study of the interphase tension is of great theoretical and practical interest, but at present there are no direct methods for its determination. 

Fortunately, a great deal of work has been accomplished in a short time, and notably by aircraft manufacturers as well as adhesives suppliers. There are several important contributions in this area. First, in the area of FPL etch, the important consideration is what kind of bonding surface is provided by the preparation method. The chromic acid/sulfuric acid not only removes air oxide and leaves base metal it also has a chemical potential which produces a very thin anodic type oxide layer of the surface. This oxide layer is porous, due to the dissolving action of the strong acid mixture, and thus the surface produced may be characterized as a thin, porous anodic oxide. (A. W. Smith compared it to a 3V chromic acid anodize based on impedance measurements.) The optimum conditions for this etch as to time, temperature, and composition have been studied at Fokker and by Smith and generally a somewhat higher concentration of sodium dichromate or chromic acid was recommended than was commonly used. 

To quantify the interaction of solute in the gaseous form with the polymer blend layer, the surface energy, ys, may be obtained. The dispersive component of the surface energy describes the interactions due to dispersive forces or a combination of dispersive forces with H-bonding or with dipole-dipole forces, Fowkes 44) first reported this method of characterization. Fowkes 44) determined the surface energy of several components. Generally, the contribution of dispersive forces and all other types of forces can be expressed as the energy of adhesion, as follows ... 

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