Toughened, two component epoxy for bonding, sealing and encapsulation

Key Features

  • Withstands rigorous thermal cycling
  • Superior durability
  • Low exotherm during cure
  • Long working life
  • Cures at ambient temperatures
  • Withstands 1,000 hours 85°C/85% RH

Product Description

Master Bond EP21FL is a lower viscosity, two component, flexibilized epoxy resin system for high performance bonding, coating, sealing and encapsulating. It is formulated to cure at room temperature or more rapidly at elevated temperatures, with a four to one mix ratio by weight. The optimum cures schedule is overnight at room temperature followed by 2-3 hours at 150-200°F. Especially noteworthy is its very long open time as indicated below. This compound is 100% reactive and does not contain any solvents or diluents.

EP21FL bonds well to a variety of substrates, including metals, glass, ceramics and many plastics. Since it is a toughened system, it is ideal for bonding dissimilar substrates with differing coefficients of expansion. It is effective for bonding materials that might be subjected to rigorous thermal cycling as well as thermal and mechanical shocks. EP21FL is an effective potting material, particularly for larger encapsulations. Its excellent electrical insulation properties are especially significant. It is resistant to chemicals including water, fuels and oils. The temperature range is -100°F to +250°F. Part A is clear and the color of Part B is amber-clear. Master Bond EP21FL can be used advantageously in electronic, electrical, optical, aerospace and specialty OEM applications, among others.

Product Advantages

  • Convenient handling
  • Low exotherm, long working life
  • Low viscosity; easily applied for bonding, coating and encapsulation
  • Outstanding ability to withstand thermal cycling
  • Excellent electrical insulation properties

Industrial Certifications

1,000 Hours at 85°C/85% RH



Double Barrel Cartridge


Gun Applicator

Premixed & Frozen Syringe


EP21FL is available is various sizes and units to accommodate customer's needs.

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