Specialty adhesives, sealants, and compounds are specialized and/or proprietary products with unique chemistries, cure technologies, and compositions.

Types of Specialty Adhesives, Sealants, and Compounds

Adhesives are organic or inorganic chemical compounds used to join components.

Sealants are liquid compounds that prevent leaks and block the ingress of unwanted materials. There are many different types of specialty adhesives, sealants and compounds. Examples include levelers, fillers, chocking materials, mastics, caulks, grouts, and thread lockers.

Specifications

Chemical System

Specialty adhesives, sealants, and compounds use many different chemical systems. Some contain acetals, acrylics, or vinyl systems. Others contain bituminous substances, butyls, ceramic or inorganic cements, cyanoacrylates, ethylene copolymers, styrene copolymers, fluropolymers, glues and gums, phenolics, formaldehyde resins, polyamides, or polyimides.

Curing

There are several curing technologies for specialty adhesives, sealants and compounds. Examples include air setting, film drying, and anaerobic curing.

• Many 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 with radiation, electron beam irradiation, visible light, or ultraviolet (UV) light.
• 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.
• Pressure sensitive adhesives (PSA) and non-corrosive curing systems for specialty adhesives, sealants and compounds are also available.

Applications

Specialty adhesives, sealants and compounds 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.

Specialty adhesives, sealants, and compounds 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 specialty adhesives, sealants and compounds.

Specialty adhesives are frequently required for specialty applications. For example, products with very high temperature resistance may be used in the aerospace industry, while adhesives featuring high resistance to acids, bases, and strong solvents are used in extreme environments.

Standards

Specialty adhesives must adhere to certain standards and specifications to ensure proper design and function. 

9982190 - This specification covers an adhesive for bonding injection molded PVC to stainless steel or nickel-chrome plated steel moldings. The adhesive shall be a smooth homogeneous mixture free from lumps and unmixed particles. The adhesive bond is obtained through the use of heat and pressure.

A-A-50272 - This Commercial Item Description (CID) covers two types of room temperature curing, epoxy adhesives. These epoxy adhesives are intended for bonding metal to metal, metal to plastic, plastic to plastic, and electronic components to boards or metal surfaces where excellent physical and electrical properties are required.

ASTM C916 - This specification covers minimum material requirements, and safety precautions in application, for adhesives to bond thermal insulation duct liner on the interior surfaces of sheet metal air conditioning ducts; and for coating exposed edges and joints of duct liner thermal insulation to minimize erosion of insulation fibers by air movement.

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Transtar | Applied Industrial Technologies