Flowable Silicone Offers Thermal Cycling and Shock Resistance

Master Bond MasterSil 323 is a two component, addition cured system for bonding, sealing and potting applications. This product has a convenient to use 1:1 mix ratio, and can be packaged in double barrel cartridges for dispensing from a gun applicator. It can be applied in thin and thick sections. This silicone has excellent flexibility, with an elongation of 150-250% at room temperature, a Shore A hardness of 35-45 and a low tensile modulus of 100-175 psi at 75°F for stress relief. It is capable of withstanding rigorous thermal cycling and shock without cracking or exerting stress on components. Additionally, MasterSil 323 has a low dielectric constant of 2.8 at 75°F, 1 MHz.

“MasterSil 323 is a specialty compound which not only offers strain relief upon cure, but also provides decent bond strength to a variety of substrates, especially considering that it is a silicone,” says Senior Product Engineer Rohit Ramnath. “The lap shear strength for an aluminum to aluminum bond joint is around 200-250 psi at 75°F. Moreover, MasterSil 323 is optically clear in thinner sections and has a refractive index of 1.44 at 589 nm. It has a wide service temperature range of -65°F to 400°F.”

The optimal cure schedule for MasterSil 323 is overnight at room temperature followed by 2-4 hours at 135-165°F. The material will fully cure without exposure to air or humidity. The working life of a mixed 100 gram batch is approximately 2-3 hours. It also has extremely low shrinkage upon curing. MasterSil 323 is available for use in ½ pint, pint, quart, gallon kit containers, 30 cc syringe kits, and 50 cc double barrel cartridges for gun dispensers. Shelf life in original, unopened containers at 75°F is 6 months.

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