Description

Anaerobic adhesives and anaerobic sealants cure in the absence of air or oxygen. They are designed for fastening and sealing applications in which a tight seal must be formed without light, heat or oxygen.

Anerobic adhesives and sealants cure when exposed to metal ion, typcially from metal surfaces of threads or joints on fasteners, fittings, and connectors. Heat, primers or activators can be used to accelerate the cure.

Substrate, or material compatibility, is an important factor to consider when selecting anaerobic adhesives and anaerobic sealants.

Some products adhere to:

• Ceramics or glass
• Concrete or masonry
• Metal
• Paper
• Plastic
• Rubber or porous surfaces

Others are compatible with substrates or materials made from composites, textiles, fabrics, wood, rubber, or elastomers.

Products that can bond dissimilar substrates such as metal to rubber are also available.

Chemical and Polymer Systems

Anaerobic adhesives and anaerobic sealants use many different chemical and polymer systems. Some systems contain:

Monomer - methacrylate esters are used in almost all anaerobic products. Acrylates, acrylic and methacrylic acids, and other vinyl polymerizable monomers may be used for special purposes.

Specifications

Selecting anaerobic adhesives and anaerobic sealants requires an analysis of mechanical, thermal, electrical and optical properties. Mechanical properties include:

• Tensile strength (break)
• Tensile modulus
• Elongation

Thermal properties for anaerobic adhesives and anaerobic sealants include:

• Use temperature
• Thermal conductivity
• Coefficient of thermal expansion (CTE)

Thermal conductivity is the linear heat transfer per unit area for a specific temperature. CTE is the amount of linear expansion or shrinkage that occurs in a material with a change in temperature.

Resistivity, dielectric strength, and dielectric constant are important electrical properties for hot melt adhesives. Optical properties include index of refraction, a measure of the speed of light in a material.

Features

Anaerobic adhesives and anaerobic sealants differ in terms of features. Flame retardant products are designed to reduce the spread of flame or resist ignition when exposed to high temperatures. Flexible or dampening products are designed to reduce sound, shock, or vibration.

Solvent-based anaerobic adhesives use a volatile organic compound (VOC) to thin or alter viscosity.

Water-based or water borne adhesive resins do not. In terms of shape or form, anaerobic adhesives and anaerobic sealants can be cast, extruded, or molded.

Thermal interface materials use a phase change to enhance thermal characteristics or heat absorption from electronic devices or electrical components.

Applications

Anaerobic adhesives and anaerobic sealants are used in many industries and applications. For example, some products are used in:

• Aerospace
• Automotive
• Marine
• Military
• Photonics
• Optical
• Tooling application

Others are designed for use with:

• Electronic devices
• Electrical power products
• High voltage applications
• Semiconductors
• Integrated circuit (IC) packaging

Anaerobic adhesives and anaerobic sealants 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).

Standards

ASTM D5363 - Standard specification for anaerobic single-component adhesives (AN). 

BS 5350-G2 - Methods of test for adhesives - part g2: determination of static shear strength of anaerobic adhesives. 

BS EN 15275 - Structural adhesives - characterisation of anaerobic adhesives for co-axial metallic assembly in building and civil engineering structures.

DIN EN 15865 - Adhesives - determination of torque strength of anaerobic adhesives on threaded fasteners.

9985253 - Sealant compound, pipe, anaerobic, grade 253.  

References

Adhesive Systems, Inc., "What Is The Anaerobic Adhesive Chemistry And Exactly How Does It Work?"

Handbook of Adhesive Technology, Second Edition, Revised and Expanded, Ch. 39

Reliable Plant and Lean Manufacturing Journal

Image Credits:

ND Industries, Inc. | Henkel Corporation | 3M Industrial Adhesives & Tapes