Epoxy Encapsulants, Silicone Potting Compound, Electronic Potting Compound

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Tough-Seal 21 Sealant for Thermal Cycling

Tough-Seal 21 Sealant for Thermal Cycling


	Tough-Seal 21 is a sealant for potting electrical and electronic components when premium thermal cycling performance is required. It delivers low embedment stress upon cure and during thermal cycle exposures. This inherent resilience from these epoxy encapsulants is gentler on sensitive circuitry than urethane encapsulants while at the same time providing an exceptional encapsulating shield to protect the electrical and electronic components from the environment. Tough-Seal 21 is a two component, hybrid epoxy elastomer potting compound that does not contain isocyanates. It has a milder health and safety profile than urethane encapsulants. Tough-Seal 21 is provided in a convenient mix ratio that is easy to mix. It sets quickly at room temperature to form a hardened encapsulating polymer with exceptional flexibility to minus 40°F and elevated temperature resistance to 300°F. As an epoxy, Tough-Seal picks up where urethane encapsulants drop off, while its tough, rubbery nature delivers thermal cycling performance not typically found in epoxy potting compound materials when encapsulating the electrical and electronic components from the environment.

Key Polymer is ISO 9001 certified and has 45 years in the business of supplying specification materials to the electronic industries.

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High Elongation 350%


	Tough Seal Technicals (Typical values, not intended for specifications)
	Wet Properties Color Viscosity at 25°C (77°F) Brookfield RVT Specific Gravity Density (lbs/gal) Shelf Life		Part A Milky White 7,000 cPs #5 @ 20 rpm 1.32 11.0 3 months		Part B Black 11,000 cPs #5 @ 20 rpm 1.28 10.7 3 months		MIX Black 10,000 cPs #5 @ 20 rpm 1.29 10.8
	Shelf Life Conditions: Unopened, factory sealed containers and cartridges in factory sealed foil pouches have a shelf life of 3 months from the date of shipment at room temperature 68°F to 77°F (20°C to 25°C) OR 12 months from the date of shipment when stored at 0°F to 38°F (-18°C to 3°C). The gel time of KEY Tough-Seal 21 becomes longer as the Aside component ages beyond 3 month at room temperature. While ultimate cure and properties are unaffected by the gel time extension, the cure rate is affected beyond 3 months age. Refrigerator or freezer storage can be used to preserve gel time. Storage above 90°F (32°C) is not recommended. Contact Key Polymer to discuss the supply chain management of Tough-Seal 21 in your operation.
	Mix Ratio by Weight Mix Ratio by Volume Gel Time (100 grams)	Combine 51 Parts A-side with 100 Parts B-side by Weight Combine 1 Part A-side with 2 Parts B-side by Volume 10 minutes
	Electrical Properties Volume Resistivity Dielectric Strength Dielectric Constant Dissipation Factor Frequency 1kHz	ASTM D257 D149 D150 D150	Temperature 23°C (73°F) 23°C (73°F) 23°C (73°F) 23°C (73°F)	Value 1.33 x 10¹²Ω-cm 350 Volts/mil 6 0.06

	Mechanical Properties Lap Shear Strength Aluminum 2024T3 Bare 0.5 in² overlap 5 mil gap	ASTM D1002	Temperature 25°C (77°F)	Value 640 psi Cohesive

	Tensile Strength Elongation at Break Type I 0.125 inch thickness	D638 D638	25°C (77°F) 25°C (77°F)	350 psi 350%

	Linear Shrinkage Hardness, Shore A	D2256 D2240	25°C (77°F) 0°C (32°F) 25°C (77°F) 80°C (176°F) 100°C (212°F) 120°C (248°F) 150°C (302°F)	<0.001 in/in 58A 52A 50A 50A 50A 48A