Feb. 8, 2022
Two component epoxy system for encapsulating and coating that passes UL746A high amp arc ignition at 3.0 mm thickness with a PLC of 0

Key Features

  • Convenient handling
  • Versatile cure schedules
  • Non halogenated filler
  • UL94HB flame retardant

Master Bond has developed an epoxy system that is UL tested as per Standard 746A. This specification is referred to as High Amp Arc Ignition (HAI), and the rating system is called PLC (performance level category). The numbers range from 0 to 4, with 0 being the best. When EP21AC was cured at a thickness of 3.0 mm, it withstood 150 arcs without ignition, thereby achieving a PLC of 0. It also passed the UL94HB flammability test.

Electrical arcing is a luminous discharge of current that is formed when a strong current jumps a gap in a circuit or between two electrodes.* Arcing can arise through a number of occurrences, including breaks in the electrical insulation, corrosion, faulty insulation, exposed surfaces on the conductor, rupturing, among others. This causes the electrical current to lose its way and travel through the tainted insulation, jumping from one conductor to the other. The conduction is not controlled and the air surrounding the current is ionized and arcs, which may lead to combustion and fire. It is critical to either avoid the condition entirely, or if arcing does occur, to limit the damaging repercussions.

EP21AC is a two component, room temperature curing epoxy formulated to optimize arc resistance. It is a flowable system with an easy to use 1:1 mix ratio by weight with a relatively long working life at ambient temperature. It cures at 75°F in 2-3 days or 2-3 hours 150-175°F. The optimum cure schedule is overnight at ambient temperature followed by 4-6 hours at 135-165°F. EP21AC has low shrinkage upon cure along with excellent dimensional stability.

It bonds well to a wide variety of substrates, including metals, glass, ceramics and many plastics. It has exceptional durability, toughness and strength. It will resist thermal cycling and is serviceable over the temperature range of -60°C to +90°C. It has good chemical resistance to water, oils, fuels, acids and bases. Part A is translucent and the color of Part B is light yellow. In summary, EP21AC is a user friendly, two part epoxy, that meets the exceptionally demanding requirements of the arcing component of UL Standard 746A. This system can be utilized in electronic, electrical, aerospace, specialty OEM and virtually any situation where electrical arcing might be a concern.

Product Advantages

  • Convenient processing, 1:1 mix ratio by weight
  • Good flow properties
  • Flame retardant as per UL94HB
  • Has a UL746A PLC rating of 0 by resisting 150 arcs without igniting

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