Adhesive bonding application

Some of these techniques using electrons and photons as probes of the surface chemistry have been described in this symposium by other authors. In this paper methods of surface analyses using beams of ions will be described. Emphasis is placed on ion scattering spectrometry (ISS) and secondary ion mass spectrometry (SIMS). Examples are shown for adhesive bonding applications including determination of locus of failure, contamination, cleaning and thermal and chemical pretreatments. 

EDISON WELDING INSTITUTE 1250 Arthur E. Adams Drive, Columbus OH 43210, (614) 688-5000. Extensive research and development of joining processes, including adhesive bonding. Applications laboratory and consulting. Testing and analysis. 

Pultrusions can be fabricated by machining (drilling, sawing, etc.), bolting, riveting and adhesive bonding. Applications include structural beams, handrails, floor supports and ladders. 

It is most important to develop good working practices for adhesive bonding applications so that physical contact with these substances is avoided as far as possible. A clean working environment and careful, methodical workmanship that are required for successful adhesive bonding go a long way towards meeting this objective. 

Many adhesive bonding applications require a unique answer and it is difficult to make generalised recommendations, as you can within limits, with vulcanisation bonding. 

In efficient or critical adhesive-bonding applications, it is necessary to demonstrate that a bonded Joint will behave as required in service. Bond performance (the characteristics under the envisaged stress and environmental conditions) is assessed by a combination of analysis and testing. A iarge amount of effort has been devoted to the development of mathematical models to describe the performance of bonded joints and provide quantitative values for strength, stiffness, etc. It must be said that, despite this, it is still very difficult to produce realistic predictions of joint characteristics for all but the simplest designs and materials. It continues to be a topic of investigation. 

Adhesive Bonding Application for Current Rolling Stock.1214... 

Adhesive Bonding Applications in the Civil Construction Sector. 1265... 

Picatinny Arsenal workers also carried out a 3-year weathering program on aluminum joints, using 17 different adhesives [25]. Of the 17 adhesives, 13 were epoxies or modified epoxies, as epoxy types are most widely used in adhesive-bonding applications. In the study, only 5 of the original 17... 

Fig. 2. Illustrations of forces to which adhesive bonds are subjected, (a) A standard lap shear specimen where the black area shows the adhesive. The adherends are usually 25 mm wide and the lap area is 312.5 mm. The arrows show the direction of the normal apphcation of load, (b) A peel test where the loading configuration, shown by the arrows, is for a 180° peel test, (c) A double cantilever beam test specimen used in the evaluation of the resistance to crack propagation of an adhesive. The normal application of load is shown by the arrows. This load is appHed by a tensile testing machine or other...

In 1993, worldwide consumption of phenoHc resins exceeded 3 x 10 t slightly less than half of the total volume was produced in the United States (73). The largest-volume appHcation is in plywood adhesives, an area that accounts for ca 49% of U.S. consumption (Table 11). During the early 1980s, the volume of this apphcation more than doubled as mills converted from urea—formaldehyde (UF) to phenol—formaldehyde adhesives because of the release of formaldehyde from UF products. Other wood bonding applications account for another 15% of the volume. The next largest-volume application is insulation material at 12%. 

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. 

Another illustrative example of the application of FTIR spectroscopy to problems of interest in adhesion science is provided by the work of Taylor and Boerio on plasma polymerized silica-like films as primers for structural adhesive bonding [15]. Mostly these films have been deposited in a microwave reactor using hexamethyldisiloxane (HMDSO) as monomer and oxygen as the carrier gas. Transmission FTIR spectra of HMDSO monomer were characterized by strong... 

In primer formulations for adhesive bonding of metals, the coupling agents that are most frequently used are those based on epoxy and amine functionalities. Aqueous solutions of aminosilanes have been successfully used for obtaining stable adhesive bonds between epoxy and steel [10] and epoxy and titanium [11,12], while epoxy functional silanes are preferable for applications involving aluminum substrates [13,14], A simple solution of % epoxy functional silane in water is currently used for field repairs of military aircraft [15] where phosphoric acid anodization would be extremely difficult to carry out, and performance is deemed quite acceptable. 

The primary challenge facing adhesive bonding of metals is to obtain sufficient durability of a bonded structure. Initial bond strength in metal-polymer adhesive joints is almost invariably excellent. Challenging the application of adhesives in polymer-polymer joining, however, is the problem of obtaining a joint that is... 

For many bonding applications a variety of adhesives can perform adequately. Hot melt adhesives are normally chosen where process speed is critical. Since hot melts have no carrier vehicle (solvent or water), and thicken rapidly as they cool, they are limited in their ability to (1) penetrate low porosity substrates or wet out very rough surfaces (2) cut through or imbibe surface contaminants and (3) wet out high thermal conductivity substrates (e.g. metals). Nonetheless, hot melts are increasingly the adhesive of choice in automated production environments because of their fast set speed. 

Acrylic adhesives can also be used in automotive assembly. For example, the hem flanges between the inner and outer panel of automotive doors can be bonded with acrylic adhesives [153]. There are many smaller industrial assembly applications where acrylic adhesives are applicable. An interesting recent example is the bonding of cable splice enclosures, using a borane initiated adhesive [154]. 

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