Flowable silicone offers thermal cycling and shock resistance

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Master Bond MasterSil 323 is a two-component, addition-cured system for bonding, sealing and potting applications.

This product has a 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 is described as having 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 24°C 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 24°C, 1MHz. 

“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,” said senior product engineer Rohit Ramnath. “The lap shear strength for an aluminium to aluminium bond joint is around 200-250psi at 24°C. Moreover, MasterSil 323 is optically clear in thinner sections and has a refractive index of 1.44 at 589nm. It has a wide service temperature range of -54°C to 200°C.” 

The optimal cure schedule for MasterSil 323 is overnight at room temperature followed by 2-4 hours at 57-74°C. 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 24°C is six months.