Laminating adhesives and composite resins are cured using heat and/or heat and pressure. They are used for high load assemblies and in severe service conditions. Cured thermoset resins may soften when heated, but do not melt or flow. Phenolic, melamine, resorcinol formaldehyde, furan, polyester, polyimide and urea formaldehyde resins are thermoset adhesives that offer strong chemical bonds and good resistance to high temperatures. Other types of thermoset adhesives include:

• Acrylics
• Elastomers
• Epoxy resins
• Ceramic
• Inorganic cements
• Natural or synthetic rubbers
• Silicone compounds
• Fluropolymers
• Phenolics
• Formaldehyde resins

Common chemical systems for laminating adhesives and composite resins also include polybutadiene, polyester, vinyl ester, polysulfide, polyurethane (PUR), water-based resins, and volatile organic compounds (VOCs).

Laminating adhesives and composite resins vary in terms of material compatibility and features. Some products adhere to ceramics or glass, concrete or masonry, metal, paper, plastic, rubber, or porous surfaces. Others are compatible with substrates made from composite materials, textiles, fabrics, wood, rubber, or elastomers. Laminating adhesives and composite resins that can bond dissimilar substrates such as metal to rubber are also available.

In terms of features, thermoset adhesives that are designed for electrical and electronics applications often provide protection against electrostatic discharge (ESD), electromagnetic interference (EMI), and radio frequency interference (RFI).  Materials that are electrically conductive, resistive, insulating, or suitable for high voltage applications are also available. Flame retardant materials reduce the spread of flames or resist ignition when exposed to high temperatures. Dampening materials are used to form layers that can bend or flex without cracking or delaminating. Thermal compounds and thermal interface materials absorb heat from electronic devices or electrical components.

Specifications

Selecting laminating adhesives and composite resins requires an analysis of physical, mechanical, and thermal 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. Use temperature, thermal conductivity, and coefficient of thermal expansion (CTE) are important thermal properties. 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 thermoset adhesives. Optical properties include index of refraction, a measure of the speed of light in a material, and transmission.

Applications

Laminating adhesives and composite resins 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 thermoset adhesives.

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Ellsworth Adhesives