Higher temperature and oil tolerance as well as improved performance on passive materials are the benefits of the latest generation of Loctite retaining compounds from Henkel. These anaerobic adhesives are formulated to secure bearings, bushes and cylindrical parts into housings and onto shafts. They are high-strength products that form 100 per cent contact between mating metal surfaces so they can carry high loads and are particularly effective in combination with shrink- or press fits.
Two of the most popular products in this range are typical examples of the improved formulation. Loctite 638 and 648 are single-component acrylic adhesives that are now able to tolerate minor surface contamination from various oils such as those used for metal cutting, lubrication, corrosion resistance and protection. This, together with their ability to withstand higher operating temperatures, considerably extends the application scope of these retaining compounds.
Both products cure when confined in the absence of air between close-fitting metal surfaces, preventing loosening and leakage from shock and vibration. They also achieve a robust cure on all metals, including passive metals such as stainless steel and plated surfaces. The reliability of the joint is greater than that of a conventional unbonded assembly and the need for expensive machining and surface-finishing operations is eliminated.
Loctite 638 was originally introduced as the choice for resistance to dynamic, axial and radial loads. In addition to these inherent qualities, the latest formulation allows the product to be used in operating temperatures to 180degC. Tests also confirm it has superior heat ageing properties than its forerunner. This is a high-viscosity, fast-curing adhesive that can be used for applications which involve gap filling up to 0.25mm.
For applications requiring increased temperature resistance, Loctite 648 has always been recommended but its performance has also been improved and it can now be used effectively in service temperatures up to 200degC. It is most suitable for applications with smaller gaps up to 0.15mm.
Available now, both the upgraded Loctite 638 and 648 retaining compounds carry WRAS, DVGW and NSF certification. For more information go to www.loctite.co.uk.