New silicone system for optoelectronic applications from Master Bond
Last update on Jun 9, 2026
Formulators and engineers working on aerospace, satellite, optical, and optoelectronic assemblies can now evaluate MasterSil 981-LO, a two-component, addition-cured silicone system from Master Bond designed for bonding, sealing, coating, and encapsulating applications.
The system meets NASA low outgassing specifications, a primary qualification requirement for space-grade assemblies, and exhibits optical clarity in thin sections, according to Master Bond. It is 100% reactive, contains no solvents or diluents, and shows minimal dimensional change upon cure, which may be relevant for precision optical assemblies where substrate stress tolerance is critical.
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Offers low-modulus with good flexibility
MasterSil 981-LO features a Shore A hardness of 20–30, a low modulus, and good flexibility, with an elongation of 200–300% at 75°F. It withstands thermal shock and cycling without cracking or imparting stress on bonded components. The system is serviceable over a temperature range of -65°F to +400°F (-54°C to +204°C) and provides electrical insulation properties, including a dielectric strength of 450 volts/mil (1/8 inch thick specimen) and a volume resistivity greater than 1014 ohm-cm at 75°F. The refractive index measures 1.437.
View all electrical & electronic bonding grades by Master Bond in Master Catalog of Adhesives >>
This system features a 1:1 mix ratio by weight and a flowable, mixed viscosity of 12,500–17,500 cps at room temperature. Its 3–4 hour working life for a 100-gram batch allows time for application and processing. The recommended optimal cure schedule is overnight at room temperature, followed by 2–4 hours at 135°F to 165°F. MasterSil 981-LO bonds to a variety of substrates, including metals, glass, plastics, ceramics, and many silicone rubbers. It is available in standard packaging ranging from 30 cc syringe kits to gallon kits, and is compatible with gun dispensers for automated applications.
View all silicone grades by Master Bond in the Master Catalog of Adhesives >>