by Renee Bernstein
Epoxy formulations offer high-strength adhesives, encapsulants and protective coatings for a variety of difficult applications in the electronics, instrumentation, automotive, aerospace, repair, maintenance and medical industries. Epoxies are easy to use and are available in two-component, resin-hardener systems that cure at room temperature or one-component systems that cure at elevated temperatures. These systems provide electrical properties, high bond and shear strength, and resistance to chemicals, solvents and moisture.
In the past, use of epoxies was limited by their hardness, brittleness and inability to maintain physical properties at elevated temperatures. Today, a variety of modified resins and hardeners, additives, and fillers are being used to expand typical epoxy usage to include applications that require high-temperature service, high-temperature stability and varying degrees of flexibility.
To obtain formulations that can withstand high temperatures, engineers mix unique resins with specialty hardeners. These modified systems cure easily to form cross-linked, organic/inorganic polymers that can be used at 500° to 700°F.
In addition to extending an epoxy`s temperature rating and thermal stability, these formulations also provide higher tensile strength and improved moisture, chemical and solvent resistance. The formulations can be used to bond, coat, protect or repair applications, such as delicate electronic assemblies, electronic components, cables, heaters, motors, thermocouples, heat exchangers, exhaust pipes, manifolds and bonding brake pads.
Flexible epoxy formulations are obtained by modifying existing resin-hardener systems to include rubber-based additives, flexiblizers and adhesion promoters. The result is that they offer adhesion to a variety of surfaces. They can bond, coat or encapsulate parts that are exposed to thermal shock. They have excellent vibration and impact resistance. They can accommodate differences in coefficients of thermal expansion and bond dissimilar materials without cracking.
These epoxy formulations can be used to bond nylon, PTFE, phenolic, polycarbonates, polyphenylsulfone and other plastics. They are used to form flexible seals and gaskets, and to bond transducers, strain gauges, medical instrumentation or any other parts that are exposed to repeated thermal cycles, vibration and impact.
Formulators can combine high-temperature, resin-hardener systems and/or flexible systems with specialty fillers to offer industry-economical, easy-to-use, high-strength adhesives with high bond strength and temperature stability, and resistance to chemicals, solvents, electricity and thermal shock.
RENEE BERNSTEIN is senior applications engineer, Cotronics Corp., 3379 Shore Parkway, Brooklyn, NY 11235; (718) 646-7996; Fax: (718) 646-3028; Web site: www.cotronics.com.
