Master Bond EP21NS is a two-part epoxy employed for bonding, sealing, coating and potting/encapsulating. It includes a nanosilica filler that imparts dimensional stability and abrasion resistance. When measured according to ASTM D4060, standard test method for abrasion resistance, with CS-17 wheel for 1,000 cycles, the epoxy displays a very low weight loss of 25mg. This formulation is a dependable electrical insulation with a volume resistivity greater than 1015Ohm-cm, an excellent dielectric constant of 2.6 at 16.4GHz and a dielectric strength of 450V/mil at 75F, for a 1/8th inch thick specimen. It is serviceable over the temperature range of -80F to +250F.
This system offers a long working life and good flow properties with moderate mixed viscosity of 50,000-90,000cps. The mix ratio of the epoxy is one to one by weight, and its optimal cure time is overnight at room temperature followed by four to five hours at 150F. It provides very low shrinkage upon curing, a low coefficient of thermal expansion of 30-35 x 10-6x in/in/C and a compressive strength of 16,000-18,000psi.
This compound bonds well to an assortment of substrates including metals, composites, ceramics, glass, rubbers and many plastics. The epoxy is resistant to water and salts. It is packaged in ounce kits, half-pint kits, pint kits, and quart kits. The colour of Part A is translucent, and Part B is amber. The epoxy does not contain solvents and is RoHS compliant.