Anaerobic adhesives/sealants application

The most important application of anaerobic adhesives/sealants is as liquid lock washers for screws and bolts. Because of their strong penetrating ability, they can be applied either before or after assembly. The prevailing torque for the strongest grades is many... 

There are altogether at least thirteen different ways in which anaerobic adhesives, sealants and gasketing compounds may be used. The more important applications are discussed below. 

Vernon Krieble, chairman of the Chemistry Department at Trinity College in Hartford, Connecticut, learned about the product through his son, Robert Krieble, who was employed at General Electric. Vernon Krieble found a chemical solution to the problem by using cumene hydroperoxide (I) (see Section XII for all structures) as the initiator and packaging in half-filled oxygen-permeable polyethylene bottles [8]. He licensed the GE patent and in 1954 founded the American Sealants Corporation, which later became Loctite Corporation [9]. At the present time anaerobic adhesives and sealants are manufactured or sold on every continent by more than a dozen companies. Applications in virtually every industry, and technological iimovation, as measured by patent activity, continue unabated. 

The wide variety of applications of anaerobic adhesives and sealants is made possible by the modifications that make the viscosity appropriate to the application. An application that requires penetration into close-fitting parts should have very low viscosity, while a produet used with large, loose-fitting parts should have a high viscosity. A styrene aerylate eopolymer could be used to increase the viscosity [59]. Polymethacrylates, eellulose esters, butadiene-styrene eopolymers, acrylonitrile-butadiene-styrene copolymers, poly(vinyl ehloride), copolymers of vinyl chloride and vinyl acetate, poly(vinyl aeetate), eellulose ethers, polyesters, polyurethanes, and other thermoplastic resins have also been used to eontrol the flow eharacteristics of anaerobic sealants [60]. The flow eharaeteristies of anaerobic formulations can also be controlled by the addition of fumed siliea and other solid additives whieh can impart thixotropic properties [61]. 

The use of adhesives/sealants in both the industrial and consumer spheres has increased dramatically in the past 20 years. In the industrial segment, both reactive and nonreactive systems are used in a wide variety of applications. The increasing use of reactive systems has, however, tended to overshadow that of the nonreactive systems. Most prominent amongst the reactive systems favored in industrial applications are anaerobic sealants (methacrylate ester based), instant adhesives (alkyl cyanoacrylate ester based), acrylic (toughened) adhesives, epoxy resin adhesives, polyurethane/isocyanate-based adhesives, silicone adhesives/sealants, and phenolic resin adhesives. 

In the Automotive industry there is a trend towards complete automation of production lines. In the application of adhesives/sealants for gasketing, the principles of dispensing have normally been to use a pressure-time system, or alternatively a cartridge system with a robotic head. However, a faster system is to screen print an anaerobic on to the surface of a component. 

Anaerobic adhesives are frequently used as sealants in various applications. Of these, perhaps the most useful illustrations are the sealing of pipes, whether unions are intended to be permanent or dismountable for maintenance. 

The use of anaerobic adhesives has become increasingly popular in appliance assembly applications, as they provide a number of manufacturing benefits. Typically used to augment the seal or holding force of a mechanically joined appliance assembly, anaerobic adhesives serve as threadlockers, thread sealants, retaining materials, and flange sealants [19]. 

All anaerobic-curing adhesives consist of a monomer, an initiator, one or more accelerators, and stabilizers. The properties of the cured and uncured adhesives can be modified to control viscosity, color, or fluorescence, reduce strength, increase toughness or heat resistance, provide lubrication and reduce settling of solid fillers. In some applications anaerobic sealants cure more rapidly if the surface is treated with chemicals which catalyze their polymerization. 

Plonchak, M., Applications Grow for Anaerobic Sealants and Adhesives, Adhesives Age, 45 (Nov. 1972). 

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