Though it has been developed for many centuries and continues to be improved, threadlocker have the tendency to fail. The failures of the fastener can be attributed to two reasons – tension relaxation and self-loosening. Tension relaxation is often a result of the changes in the temperature which includes the expansion as well as contraction of the bolts and materials used as substrate. When this happens, the tension in the bolt is reduced and the clamping force is not the same as the one set during assembly. Self-loosening, on the other hand, is a result of the lateral sliding action among the fasteners and the surface they are in contact with. There are many different mechanical ways that have been developed to solve the issue of fasteners loosening including locking bolts, wire retainer and spring washers. Despite these mechanical locking methods, the sliding motion still cannot be controlled which is the very reason for self-loosening. Furthermore, these methods make the fastener assembly costs higher.
Comes the chemical adhesive used in threadlocker which is cheaper and is permanent thereby preventing the failure of the threaded fasteners. These adhesives were introduced by the Loctite Corporation around 50 years have passed. These anaerobic adhesives consist of single component and are in the form of liquid resins. It undergoes curing process in order to become tough as a solid with the aid of metal ions in a vacuum setting. The mechanism employed for the anaerobic curing made it possible for the adhesive to become fluid and spread evenly before settling in the grooves present among the threaded fasteners. All of these are done while making sure that there is no premature curing. The excess will just overflow and this can be wiped away since it remains in the liquid state.
During the curing process of the liquid threadlocker, it creates polymer chains that fill any imperfection inside the threads. The adhesive is then responsible in filling the very small gaps among the threads to create a positive lock and seal the assembly together. When this s done, there is no chance for lateral movements and it also acts as protection for the joint.