The air surrounding the current becomes ionized and arcs, which may lead to combustion and fire. 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. EP21AC is designed primarily with the aim to prevent arcing related issues.
The US manufacturer has tested the material against United Laboratories, UL, test criteria. “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,” says 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 to 20%, and is capable of resisting thermo-mechanical stresses. It is described as an excellent electrical insulator with a volume resistivity greater than 1014 ohm-cm, and a dielectric constant of 4.7 at 24°C. Other noteworthy 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].
EP21AC has a one-to-one mix ratio by weight and cures at room temperature, or more rapidly with heat. It is said to have good flow properties with a mixed viscosity of 30,000-50,000 cps, and a relatively long working life of 75-120 minutes at room temperature. This compound bonds well to a variety of substrates including metals, ceramics, composites and many plastics and rubbers. It is available for use in ounce kits, ½ pint, pint, quart and gallon container kits. Specialty packaging is also available in premixed and frozen syringes.