Adhesion bonding, surface characterization

Surface Morphology. The initial Integrity of an adhesively bonded system depends on the surface oxide porosity and microscopic roughness features resulting from etching or anodization pretreatments. (17) The SAA surface characterized in this study consists of a thick (9 ym), porous columnar layer which provides excellent corrosion resistance in both humid and aggressive (i.e., Cl ) media. I The thinner FPL oxide provides a suitable substrate surface for evaluating the candidate inhibitors. 

Gettings, M., Kinloch, A. J. Surface characterization and adhesive bonding of stainless steels. U. K. Atomic Energy Authority, Elarwell, England, 1978... 

Adhesive wear is characterized by transfer of material from one material to another during sliding as a result of the adhesive forces at the contact points. The transferred material accumulates until the surface forces cause wear particles to form 50). Because the rate at which polymeric material transfers depends on the bonding at the contact point — Coulombic and van der Waals — adhesive wear is usually small compared... 

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... 

Aspects of adhesive bonding and applicable surface characterization methods1... 

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. 

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

Synthetic surfactants and polymers are probably most often used to modify the characteristics of a solid surface, i.e., they function at the solid - liquid interface, such as in the processes of detergency, lubrication, or the formation of adhesive bonds. The performance of modem FT - IR spectrometers is such that many new applications to the characterization of the solid - liquid interface, particularly in kinetics studies, are possible. Reflection - absorption spectroscopy and attenuated total reflectance (ATR) techniques have been applied to "wet" interfaces, even the air - water interface, and have figured prominently in recent studies of "self -assembled" mono - and multilayers. 

One of the benefits of surface treatment prior to adhesive bonding is that it not only removes weak boundary layers such as contamination, but also provides a more consistent surface to which the adhesive can bond. Common surface treatments used for metal substrates are characterized generally in Table 16.2. 

Tadepalli and Thompson focused on the bonding strength of copper-to-copper bonded structures using four-point bending characterization [66]. Adhesion energy was characterized for three different surface preparation... 

Independent of the chemical structure, industrially available adhesives are characterized by the formation of strong adhesive bonds on the respectively pretreated surfaces of the materials described. This results in the criteria for adhesive selection described in Chapter 8. 

In order to understand the aim of surface treatments for composite bonding, we wiU concentrate on a real composite bonding problem for aeronautical purposes. Since classical surface treatments like peel ply can be limited by a cohesive failure occurring in the material, we wiU focus on a new kind of surface treatment (excimer laser) which can completely change surface parameters. The different aspects are presented in two steps the first consists in the surface characterization of the composite material and the second is related to results of destructive single lap shear tests of composite assemblies. Finally, both steps are Hnked in order to derive general mles on phenomena governing adhesion properties of polymer composites. 

The outline of this chapter is as follows. The spectroscopic techniques that can be used for surface of interface characterization of adhesively bonded materials are listed in Table 1. The most popular techniques are then discussed briefly in terms of the type of information they provide and where they can be applied. Their limitations are also described briefly. Since just a handful of techniques are used on a regular basis, notably XPS, AES, SIMS, FTIR, and Raman spectroscopy, only these techniques will be discussed in detail. Recent and ongoing instrumental developments are described and specific applications of each of these techniques are presented and discussed. Finally, a bibliography containing many references to textbooks and important artieles is given. 

The techniques highlighted here are XPS, AES, SIMS, various forms of FTIR, Raman spectroscopies, and HREELS. This selection is based on their relative ease of application and interpretation, their commercial availability, and the unique capabilities that each technique possesses for the study of an aspect of adhesive bonding. These capabilities are also highly complementary. The applications discussed are chosen to illustrate the applications in three major areas described earlier surface characterization, modification of metal or polymer surfaces, and analysis of interfaces. 

This chapter summarizes the principles of some of the many spectroscopic techniques that are available for the analysis or study of aspects of adhesive bonding science and technology. As indicated in Table 1, there are dozens of techniques and new acronyms appear almost on a daily basis. The number of instrumental spectroscopies available today to the scientist is bewildering, especially the many techniques for surface characterization. Therefore, it is likely that some techniques have been missed, although it was attempted to cover them all, at least in Table 1. The choice of techniques from that listing that were actually discussed in this chapter had to be limited and was in some cases somewhat arbitrary and subjective. However, some emphasis was put on techniques that can be used in the study of the science of adhesive bonding technology. Techniques for routine analysis, e.g., NMR or the various mass spectrometries, were not discussed in depth. 

Studies of the dynamic mechanical properties of polymeric objects characterized by the adhesion bond with a solid surface found that the gradient of the segmental mobility and of the indices of the mechanical properties was close to the interphase boundary during withdrawal from the solid surface. 

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. 

The strength of adhesive-bonded joints under the combined effect of tangential and normal stresses at 20, 40, 60, 90, and 100 days after cementing of St3 steel is displayed in Fig. 3.9 as surface stress plotted in coordinates cr—Taj time. Surface I characterizes the extreme stresses of the joints using VAK adhesive surface II is the same without addition of ATG to the adhesive. 

---