Fluid Silicone Offers Thermal Cycling and Shock Resistance

Master Bond MasterSil 323 is a two-component, addition-cure system for adhesive, sealant and potting applications. The product has a 1:1 mix ratio and can be packaged in dual-barrel cartridges for dispensing from a caulking gun. It is applicable in both thin and thick sections. This silicone exhibits excellent flexibility with 150-250% elongation at room temperature for stress relief, 35-45 Shore A hardness, and a low tensile modulus of 100-175 psi at 75°F. The components can withstand demanding thermal cycling and shock without cracking or stress on the substrate. Additionally, MasterSil 323 has a low dielectric constant of 2.8 at 75°F and 1 MHz. Senior Product Engineer Rohit Ramnath stated, "MasterSil 323 is a special compound that not only provides stress relief upon cure, but also delivers good adhesion to various surfaces, particularly noteworthy given that it is a silicone," and added "For an aluminum-to-aluminum bonded joint, the lap shear strength is approximately 200-250 psi at 75°F." Additionally, MasterSil 323 is optically transparent in thinner sections and has a refractive index of 1.44 at 589 nm. It has a wide service temperature range from -65°F to 400°F. The optimum cure schedule is overnight at room temperature followed by 2-4 hours at 135-165°F. The material fully cures without exposure to air or moisture. The working life of a 100-gram mixed batch is approximately 2-3 hours. It also exhibits extremely low shrinkage during cure. MasterSil 323 is available in ½ pint, pint, quart and gallon kits, in 30 cc syringe kits, and in 50 cc dual-barrel cartridges for caulking gun dispensers. Shelf life at 75°F in original, unopened containers is 6 months.   Source