Adhesives for Mechanical Applications

In this range of applications, adhesives are used for fastener locking, formed-in-place gaskets, and bonding of mechanical parts. Mainly cyanoacrylates, anaerobic and encap­sulated adhesives, modified acrylates, and elastomer or resin-based compounds are applied. Examples of applications are listed in Table 1. To choose a suitable adhesive, the required strength and mechanical properties as well as the chemical conditions for the specific application should be well known. For example, for the curing of dimetha­crylates, the catalytic effect of the glued surface, the absence of oxygen, the temperature, the mold of the bond line, and the type of material to be bonded are important. Depending on the type of bonding, the requirements differ. The bond strength, temperature and aging stability, and the resistance to chemical reagents must fit the application load. The specific conditions of the joint performance have to be taken into consideration.

Table 1 Adhesive and Sealant Applications in Mechanical Parts Production

Type of adhesive

Method of curing


Anaerobic adhesives

Absence of oxygen and


metal contact

Flat surface bonding Adhesive bonding of electric and electronical components Fastener locking Shaft/hub bonding



Gaskets Thread sealing Flat surface bonding Bonding of caps in cylinder head covers, gearboxes, crankcases, axle housings Shaft/hub bonding

Epoxy resin adhesive foils

Heat treatment

Bonding of heat exchanger

Synthetic resin

Solvent evaporation



Common sealing


Anaerobic or with

Fastener locking


hardener after bursting of the capsules

Modified acrylates

Activator and absence of oxygen

Bonding of flat surfaces


Heat treatment

Bonding of brake straps

adhesive foils

Bonding of clutch and brake linings

Silicone rubbers

Moisture or hardener

Sealing of oil pans and housing covers

Figure 2 Examples of fasteners coated with encapsulated adhesives. (Courtesy of Loctite Deutschland GmbH).

For adhesive bonding of plastics to plastics and plastics to metal the cyanoacrylates are usually better than anaerobic compounds, which are more suitable for metal-to-metal bonding because of their greater resistance to mechanical vibrations and impacts. Encapsulated adhesives can be used to coat the fastener by the supplier. The curing takes place after fastening and locking are done. Figure 2 shows the great variety of available coated fasteners. Formed-in-place gaskets and adhesive sealants are used in various mechanical applications to seal and bond surfaces. There are cyanoacrylates, anaerobic adhesives, and modified acrylates and solvent-based rubber or resin compounds as well as silicones. The products are applied manually or automatically on the surfaces just prior to assembly. Figure 3 shows a sealant application extruded automatically onto an oil pan flange.

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