Mechanical engineering, anaerobic

The special role of anaerobic adhesives in mechanical engineering... 

Anaerobic adhesives were created specifically for assembling a wide variety of mechanical engineering components. The impact their properties and use have on fundamental design concepts is discussed in relation to other types of adhesives in Chapter 2. What this approach does not demonstrate is the overall value of these unique materials to the mechanical engineer in a wide range of situations, nor does it show the degree to which the characteristics of individual grades are matched to the intended end use. 

A few illustrative case histories provide a feel for the application scope of anaerobics in mechanical engineering. The eight examples below cover the main outlets for materials of this type. 

Dragoni, E., Mauri, P. (2002). Cumulative static strength of tightened joints bonded with anaerobic adhesives. Proceedings of the Institution of Mechanical Engineers, Part L Journal of Materials Design and Applications, 216(1), 9-15. 

Pavlostathis, S.G., Gossett, J.M., 1988. Preliminary conversion mechanisms in anaerobic digestion of biological sludges. Journal of Environmental Engineering and Science 114, 575-592. 

Yoo ES, Libra J, Adrian L (2001) Mechanism of decolorization of azo dyes in anaerobic mixed culture. J Env Engin 127 844—849... 

Essentially limited as a class to co-axial mechanical assembly, retention and sealing, they also make good general purpose gasketting media. The cure rate depends upon surface activity and may require a supplementary catalyst. The family copes with the gaps of normal engineering practice. As clearances increase, the anaerobics capacity to cope well falls rapidly. The majority of materials in the family are only suitable for use in lap joints as gasketting media or to seal a gap. Only the special anaerobic materials can be considered to be true adhesives and suitable for use on unsupported lap joints. 

Fig. 7.2. The major engineering joints, (a) The lap joint this simple form, and its many variants, is the basis of most bonded structures, (b) The co-axial joint this form is particularly suited to the assembly of mechanical components. The anaerobic adhesives employed are normally quite different in nature from those...

Epoxy adhesives such as Huntman s Araldite AW 134 with HY 994 hardener (cured for 15 min at 120°C) and Araldite AV 1566 GB (cured for 1 h at 230°C) give the best results with this engineering resin. Other adhesives that can be used are cyanoacrylate (Loctite 414 with AC primer), anaerobics (Loctite 638 with N primer), and silicone sealant (Loctite Superflex). The highest lap-shear strength was obtained with Araldite AW 134. This adhesive has balanced properties, good resistance to mechanical shock, thermal resistance to 100°C, and reasonable stability in the presence of aliphatic and aromatic solvents. Some solvents, particularly chlorinated hydrocarbons, will cause deterioration of the bond [30]. 

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