How to Select Thermoset Adhesives
Image credit: All-Spec Industries | Acrolab Ltd. | R.S. Hughes Company, Inc.
Thermoset adhesives are crosslinked polymeric resins that are cured using heat and/or heat and pressure.
Understanding Thermoset Adhesives
Thermoset adhesives represent a number of different substances that undergo a chemical reaction when curing, such that the structure formed has superior strength and environmental resistance. Despite their name, thermosets may or may not require heat to cure and may instead use irradiation or electron beam processing. Due to their superior strength and resistance, thermosets are widely used for structural load-bearing applications; they also tend to be more expensive than other adhesives for this reason.
One Component vs. Two Component Systems
Thermoset adhesives are available as one- or (more commonly) two-component systems. One component systems use heat curing and require cold storage for sufficient shelf life. Most one component adhesives are sold as pastes and applied by a trowel to easily fill gaps.
Two component systems must be mixed and applied within a set time frame, ranging from a few minutes to hours. Two component epoxies are suitable for bonding nearly all substrates and feature high strength and chemical resistance as well as excellent long-term stability. Despite these superior characteristics, two component systems are often avoided in favor of one component ones due to the latter's easier use and storage requirements.
The image below shows a thermoset compound cross-linking as heat is applied.
Image credit: American Laboratory
Specifications
Substrate Material and Systems
Common thermoset adhesive materials include epoxy resin, phenolic formaldehyde (PF) resins, phenolic neoprene, resorcinol formaldehydes (RF), polyesters, and polyimides. The table below details some of these common materials and the substrates they effectively bond to.
|
System |
Material Compatibility |
|||||||
|
*** |
Ceramic |
Concrete |
Metal |
Plastic |
Porous |
Rubber |
Textiles |
Wood |
|
Phenol PF |
x |
|
x |
x |
|
|
|
x |
|
RF |
x |
x |
|
|
|
|
x |
x |
|
Polyester |
x |
|
|
|
|
|
|
x |
|
Polyimides |
|
|
x |
|
|
|
|
|
|
Epoxies |
x |
x |
x |
x |
x |
x |
|
x |
|
Redux adhesive |
x |
|
|
x |
|
x |
x |
|
Table credit: RoyMech
For more detailed information about adhesive and sealant materials and substrates, please visit GlobalSpec's Industrial Sealants Selection Guide.
References
American Laboratory - Thermosets: How to Avoid Incomplete Curing
AZOM - Thermosetting Adhesive Systems
Related Products & Services
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Conformal Coatings
Conformal coatings encapsulate circuit boards and their electronic components in order to prevent the ingress of moisture, fungus, dust and other environmental contaminants.
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Epoxy Adhesives
Epoxy adhesives are chemical compounds for joining components. They require clean surfaces and are valued for their toughness and resistance to chemical and environmental damage.
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Gel Elastomers
Gel elastomers are highly viscoelastic polymer gel materials that have excellent shock absorption and damping characteristics. They are available in a variety of material types and grades.
-
Pressure Sensitive Adhesives (PSA) and Contact Adhesives
Pressure sensitive adhesives (PSA) and contact adhesives adhere to most surfaces with very slight pressure. They are available in solvent and latex or water-based forms.
-
Silicone Adhesives and Sealants
Silicone adhesives and sealants have a high degree of flexibility and a very high temperature resistance (up to 600° F), but lack the strength of other epoxy or acrylic resins.
-
Thermoplastics and Thermoplastic Materials
Thermoplastics and thermoplastic materials soften when heated and harden when cooled. They can withstand many heating and cooling cycles and are often suitable for recycling.
-
Thermosets and Thermoset Materials
Thermosets and thermoset materials are crosslinked polymeric resins that are cured or set using heat or heat and pressure. They generally have a higher resistance to heat than thermoplastics.
