Master Bond EP21AC is a two-part epoxy with a non-halogenated filler that is formulated for applications where arc resistance and flame retardancy are required. Electrical arcing is a challenge for numerous electronic or electrical devices; this occurs when electricity jumps from one connection to another, resulting in an electrical breakdown. The air surrounding the current becomes ionized and arcs, which may lead to combustion and fire. Master Bond reports that EP21AC is designed primarily with the aim to prevent arcing related issues.

“EP21AC withstood over 150 arcs without igniting and therefore was assigned the highest PLC (Performance Level Category) of 0 under the UL746A High Amp Arc Ignition test,” said Rohit Ramnath, senior product engineer. “The compound is also flame retardant, as per the UL94HB standard for flammability testing. This combination of unique performance properties makes EP21AC suitable for encapsulating, potting or coating in many demanding applications.”

The system is toughened, with an elongation of 10-20%, and is capable of resisting thermomechanical stresses. It is reportedly an excellent electrical insulator, with a volume resistivity greater than 1014 ohm-cm and a dielectric constant of 4.7 at 75°F. Additional properties include a tensile strength of 5,000-6,000 psi and a tensile modulus of 300,000-350,000 psi at 75°F. It is serviceable over the temperature range of -60°C to 90°C (-75°F to 194°F).

Master Bond reports that EP21AC has a convenient-to-use 1:1 mix ratio by weight and cures at room temperature (more rapidly with heat). It has good flow properties, with a mixed viscosity of 30,000-50,000 cps, and a relatively long working life of 75-120 min at room temperature. This compound bonds well to a variety of substrates, including metals, ceramics, composites, and many plastics and rubbers.

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