Thread Lockers and Retainers

Thread lockers and retainers are used to render threaded fasteners immovable. They are used mainly with devices that are subject to transverse and axial loads that may lead to vibrational loosening. There are two basic types of thread lockers and retainers: adhesives and sealants. Adhesives are organic or inorganic chemical compounds for joining compounds. Sealants are liquid compounds that prevent leaks and block the ingress of unwanted materials. Some thread lockers and retainers are compatible with materials made of ceramics, glass, concrete, masonry, metal, plastic, or wood. Others adhere to porous surfaces or composite materials. Products that can bond dissimilar substrates such as metal to rubber are also available.

Thread lockers and retainers differ in terms of chemical systems and curing technologies. Some chemical systems contain acrylics, elastomers, natural or synthetic rubbers, epoxy resins, silicone compounds, or vinyl systems. Others contain cryanoacrylates, ethylene copolymers, styrene copolymers polybutadiene, polysulphide, or polyurethane (PUR). Many curing technologies for thread lockers and retainers are available. Typically, thermoplastics and hot melt adhesives are cured using heat or heat and pressure. Vulcanization, a thermosetting reaction, uses heat and/or pressure in conjunction with a vulcanizing agent to produce materials with greatly increased strength, stability, and elasticity. Some materials cure or vulcanize at room temperature. Others cure in the absence of oxygen or react with moisture. Single component curing systems consist of a resin that hardens through the application of heat or a reaction with surface moisture. Two-component and multi-component curing systems consist of two or more resins and a hardener, crosslinker, activator or catalyst. 

Selecting thread lockers requires an analysis of physical, mechanical, thermal, electrical and optical properties. Physical properties include viscosity and gap fill, the space between the material and the substrate. Mechanical properties include tensile strength and elongation, the percentage amount of deformation. Thermal properties consist of use temperature, thermal conductivity, and the coefficient of thermal expansion (CTE). Resistivity, dielectric strength, and relative permittivity are important electrical properties. Optical properties include index of refraction, a measure of the speed of light in a material, and transmission. 

Thread lockers and retainers vary in terms of features. Products that are designed for electrical and electronics applications often provide protection against electrostatic discharge (ESD), electromagnetic interference (EMI), and radio frequency interference (RFI). Filled or reinforce compounds consist of resins with additional modifiers such as fillers, pigments, or chopped fibers. Flexible adhesives and sealants form a layer that can bend or flex without cracking or delaminating. Flame retardant materials resist ignition or reduce the spread of flame when exposed to high temperatures.

Thread lockers and retainers are used in many industries and applications. Some products are used in aerospace, automotive, marine, military, photonics, optical, or tooling applications. Others are designed for use with electrical power products, high voltage applications, semiconductors, or integrated circuit (IC) packaging. Materials that are suitable for medical, pharmaceutical and food processing applications meet requirements established by the Food and Drug Administration (FDA) and the U.S. Department of Agriculture (USDA). Original equipment manufacturers (OEMs) and repair, maintenance and overhaul (MRO) organizations also use thread lockers and retainers.

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