Adhesive Bonding Techniques

Adhesive Bonding Technique. Standard procedures for preparing adhesive bond specimens were used. The composite was initially sanded with 240 grit emery paper and then thoroughly rinsed with methylene chloride. Steel substrates were rinsed thoroughly with methylene chloride. Bonds were prepared as one inch overlap shear specimens bond thickness was 0.75 mm. Bond thickness was defined using 1.5 mm long wires of the appropriate thickness. 

Cagle, C. V., Adhesives Bonding Techniques and Applications, McGraw-Hill, New York, 1968. 

Adhesive properties were monitored both directly and indirectly. Direct measurements included changes in shear strength and Tg (glass transition temperature) of adhesive. Indirect measurements include those changes in mirror properties such as reflectance and shape which may occur as changes occur in the nature of the adhesive bond. Techniques used for the above direct and indirect measurement are summarized below. 

Weldbonding is also called spot-weld adhesive bonding. It is a method of fabricating hardware that uses both welding and adhesive bonding techniques. A layer of adhesive, either in paste or in film form, is applied to one of the metal members to be joined. The other metal member is placed on top, forming a lap-type joint, and the assembly is clamped or resistance... 

The advantages of adhesive bonding techniques for the assembly of shafts and associated components, discussed above in detail, can be summarised as follows Cracking due to excessive hoop stresses in interference-fitted parts is avoided. 

Acrylic adhesive bonding techniques, although simple, are distinct from traditional structural adhesive techniques (e.g., 1 1 mix-in or heat cure). This creates a marketing barrier requiring thorough user instruction. 

The very low surface energy of polyethylene prohibits the widespread use of adhesive bonding techniques. Even the adhesion of printing ink to polyethylene requires prior chemical modification of the surface by one of the techniques described in Chapter 7. 

Surface analysis has made enormous contributions to the field of adhesion science. It enabled investigators to probe fundamental aspects of adhesion such as the composition of anodic oxides on metals, the surface composition of polymers that have been pretreated by etching, the nature of reactions occurring at the interface between a primer and a substrate or between a primer and an adhesive, and the orientation of molecules adsorbed onto substrates. Surface analysis has also enabled adhesion scientists to determine the mechanisms responsible for failure of adhesive bonds, especially after exposure to aggressive environments. The objective of this chapter is to review the principals of surface analysis techniques including attenuated total reflection (ATR) and reflection-absorption (RAIR) infrared spectroscopy. X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and secondary ion mass spectrometry (SIMS) and to present examples of the application of each technique to important problems in adhesion science. 

With the exception of coupling agent technology, primers for structural adhesive bonding have received little theoretical treatment in the literature beyond a discussion of mechanisms of corrosion inhibition by primer additives and limited discussion about statistical techniques for primer formulation. Perhaps because of the much more widespread use and greater economic importance of corrosion-protective coatings, the design and function of primers for these systems have... 

Wegman, R.F., Surface Preparation Techniques for Adhesive Bonding. Noyes Publications, Park Ridge, NJ, 1989. 

Maturation as a technology does not mean that advancement and innovation has ceased. Adhesive bonding is so essential to the aerospace field that as long as there is a desire to go higher, faster and farther more efficiently, there will be an incentive to develop new materials and processes for adhesive bonding. Areas of particular interest for future applications are high-temperature adhesives, fiber-reinforced metal laminates and more efficient bond assembly techniques. 

New coating techniques in commercial use are mechanical coating (now incorporated under plating in Table 13.7) and adhesive-bonded or vapour-deposited coatings, although each of these represents less than 1% of the zinc coatings used. 

SURFACE PREPARATION TECHNIQUES FOR ADHESIVE BONDING by Raymond F. Wegman... 

Asphalt—mbber is mixed and applied to roadways by several techniques. In one method, mbber and asphalt are mixed at ca 175—220°C for one to two hours. The hot mixture is applied to the roadway and covered with a layer of stone chips to form a chip seal. The mbber cmmb consists of scrap tires ground into particles less than 2 mm in diameter. Rubber-modified asphalt is also used for waterproofing membranes, crack-and-joint sealers, hot-mix binders, and roofing materials. The mbber improves asphalt ductility and increases its softening point. The aggregate adhesive bond is stronger, and the asphalt lasts longer. Production of rubber-modified asphalt has increased from 405 t in 1970 to 27,000 t in 1980 (41). Typically, about 2 t of mbber is used for 1 km of roadway. If it is assumed that asphalt—mbber contains ca 25% mbber and 75% asphalt, the potential demand for scrap mbber would be ca 40,500 t/yr, or ca 2% of the amount available. 

Metals such as aluminium, steel, and titanium are the primary adherends used for adhesively bonded structure. They are never bonded directly to a polymeric adhesive, however. A protective oxide, either naturally occurring or created on the metal surface either through a chemical etching or anodization technique is provided for corrosion protection. The resultant oxide has a morphology distinct from the bulk and a surface chemistry dependent on the conditions used to form the oxide 39). Studies on various aluminum alloy compositions show that while the oxide composition is invariant with bulk composition, the oxide surface contains chemical species that are characteristic of the base alloy and the anodization bath40 42). 

Adhesive bonding for structural joint formation is attractive because it presents a number of distinct advantages over more conventional metal joining techniques, such as 1-3> ... 

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