Application Type Pot, Encapsulate 1 Part or 2 Part 2 Part Material Form Liquid, Silicone elastomer Industry Amplifiers, Connectors, Electronics, High voltage resistor packs, Sensors, Transformers, Relays Manufacturer Dow Chemistry Silicone, Silicone elastomer Cure Method Base/Curing agent Cure Temperature (°C) 20 to 25, 20 to 25 Cure Time (min) Rapid, ~14400 (Seconds), 1,440 Viscosity (cPs) 5,500, Flowable Color Black, Gray Ozone Resistance Ozone resistance Chemical Resistance Good High Temperature Resistance (°C) 200 Low Temperature Resistance (°C) -45, -55
Technical Data for Dow 255 Primerless Elastomer
- Pottant / Encapsulant - Pot, Encapsulate
1 Part or 2 Part
- 1 Part or 2 Part - 2 Part
- Part A Name - Base
- Part B Name - Curing Agent
- Elastomer - Silicone elastomer
- Silicone - Silicone elastomer
- Dispenser - Automated mixing, Dispensing equipment, Manual mixing
- 2-Part Cure - Base/Curing agent
Cure Temperature (°C) 20 to 25, 20 to 25 Test Method Cure Time (min) Rapid, ~14400 (Seconds), 1,440 Test Method Viscosity (cPs) 5,500, Flowable Work / Pot Time (min) <5.00 Test Method Mix Ratio 10:1 (by volume), 10:1 (by weight)
Shear Strength (psi) 44 Test Method
Ozone Resistance Ozone resistance Chemical Resistance Good UV Resistance UV resistance Environmental Resistance Environmental resistance High Temperature Resistance (°C) 200 Low Temperature Resistance (°C) -45, -55 Moisture/Humidity Resistance Moisture/humidity resistance
Dissipation Factor 0.01700, <0.00590 Test Method Dielectric Strength (V/mil) Good, 22,204,724, Durable Dielectric Constant 2.95, 2.83 Test Method Thermal Conductivity (W/m°K) 0.26, 2.61500039538806e-3 Volume Resistivity (O) 1.1e15 (ohms/cm)
Shore A Hardness 25 Flexibility Flexible
Specific Gravity 1.300 Coefficient of Thermal Expansion (CTE) 311 (Linear (micron/m °C or ppm )) Flash Point (°F) 122.0
Shelf Life Details Dow Corning 255 Elastomer should be kept refrigerated (10°C/50°F) until use. Any special storage and handling instructions will be printed on the product containers.
Best Practices for Dow 255 Primerless Elastomer
In applications requiring adhesion, priming will be required for the silicone encapsulants. See the Primer Selection Guide for the correct primer to use with a given product. For best results, the primer should be applied in a very thin, uniform coating and then wiped off after application. After application, it should be thoroughly air dried prior to application of the silicone elastomer. Additional instructions for primer usage can be found in the Dow Corning literature, “How To Use Dow Corning Primers and Adhesion Promoters” (Form No. 10-366) and in the information sheets specific to the individual primers.
Dow Corning silicone 10:1 encapsulants are supplied in two parts as lot-matched base and curing agent that are mixed in a ratio of 10 parts base to one part curing agent, by weight. After thoroughly mixing base and curing agent, agitate gently to reduce the amount of air introduced. Allowing the mixture to set for 30 minutes before pouring may be adequate for removal of the air introduced during mixing.
If air bubbles are still present, vacuum deairing may be required. Deair in a container with at least four times the liquid volume to allow for expansion of material. Air entrapped in the mixture can be removed by using a vacuum of 28 to 30 inches Hg. Continue the vacuum until the liquid expands and settles to its original volume and bubbling subsides. This may take 15 minutes to 2 hours depending on the amount of air introduced during stirring. For best curing results, glassware and glass or metal stirring implements should be used. Mix with a smooth action that does not introduce excess air.
If a substrate or material is questionable with respect to potentially causing inhibition of cure, it is recommended that a small scale compatibility test be run to ascertain suitability in a given application. The presence of liquid or uncured product at the interface between the questionable substrate and the cured gel indicates incompatibility and inhibition of cure.
Manufacturer's Recommended Replacement Materials
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Cure Temperature Test Methods
|Cure Temperature||Cure Time Test Method|
|20 to 25°C|
|20 to 25°C||These data were collected on 50-100 gram samples of a lot believed to be typical and should be used as initial estimates of cure times. Times will vary slightly from batch to batch and can be longer or shorter due to thermal mass of your parts and your heating ramp rate. Pretesting is recommended to confirm adequate cure for your application.|
Cure Time Test Methods
|Cure Time||Test Method|
|~14400 (Seconds)||These data were collected on 50-100 gram samples of a lot believed to be typical and should be used as initial estimates of cure times. Times will vary slightly from batch to batch and can be longer or shorter due to thermal mass of your parts and your heating ramp rate. Pretesting is recommended to confirm adequate cure for your application.|
|1,440 min||For primerless adhesion products, cure time is based on time to reach durometer. Full adhesion may take more time at cure temeprature.|
Work / Pot Time Test Methods
|Work / Pot Time||Temperature|
|<5.00 min||Room temperature|
Shear Strength Test Methods
|44 psi||Lap shear strength|
Dielectric Constant Test Methods
|Dielectric Constant||Test Method|
Dissipation Factor Test Methods
|Dissipation Factor||Test Method|