Application Type Pot, Encapsulate 1 Part or 2 Part 2 Part Material Form Liquid, Silicone elastomer Industry Electronic, High voltage transformers, Sensors, Heat sinks Manufacturer Dow Chemistry Silicone elastomer Cure Method 2 Parts Cure Temperature (°C) 20 to 25, 100, 125, 150 Viscosity (cPs) Low, 33,000, Flowable Color Gray Ozone Resistance Ozone resistance Chemical Resistance Good High Temperature Resistance (°C) 200 Low Temperature Resistance (°C) -45, -55 Key Specifications UL (Underwriters Laboratory), ULC (Underwriters Laboratories of Canada), NFPA (National Fire Protection Association): UL 94: UL 94 V-0
Technical Data for Dow 3-6655 Thermally ConDuctive Encapsulant
- Pottant / Encapsulant - Pot, Encapsulate
1 Part or 2 Part
- 1 Part or 2 Part - 2 Part
- Elastomer - Silicone elastomer
- Silicone - Silicone elastomer
- Dispenser - Automated meter-mix
- Brush - Manual
- 2-Part Cure - 2 Parts
- UL (Underwriters Laboratory), ULC (Underwriters Laboratories of Canada), NFPA (National Fire Protection Association): UL 94: V0 - UL 94 V-0
Cure Temperature (°C) 20 to 25, 100, 125, 150 Test Method Viscosity (cPs) Low, 33,000, Flowable Work / Pot Time (min) 60 Test Method
Tensile Strength (psi) 45
Ozone Resistance Ozone resistance Chemical Resistance Good UV Resistance UV resistance High Temperature Resistance (°C) 200 Low Temperature Resistance (°C) -45, -55
Dissipation Factor 0.00100, <0.00010 Test Method Dielectric Strength (V/mil) Durable, 13,582,677 Dielectric Constant 5.20, 5.20 Test Method Thermal Conductivity (W/m°K) Excellent, 1.80 Test Method Volume Resistivity (O) 1.1E+15
Elongation (%) 1 Shore OO Hardness 71 Flexibility Flexible Modulus (psi) 6.5 (Compression at (10%, psi))
Specific Gravity 2.700 Coefficient of Thermal Expansion (CTE) 145 (Linear (micron/m °C or ppm )) Flash Point (°F) 392.0
Shelf Life Details Shelf life is indicated by the “Use By” date found on the product label. For best results, Dow Corning thermally conductive materials should be stored at or below the maximum specified storage temperature. Special precautions must be taken to prevent moisture from contacting these materials. Containers should be kept tightly closed and head or air space minimized. Partially filled containers should be purged with dry air or other gases, such as nitrogen. Any special storage and handling instructions will be printed on the product containers. Shelf Life Type From date of manufacture Shelf Life (mon) 12
Not Good For
Don't Use With non-reactive metal substrates, non-reactive plastic surfaces, Teflon, polyethylene, polypropylene.
Best Practices for Dow 3-6655 Thermally ConDuctive Encapsulant
All surfaces should be thoroughly cleaned and/or degreased with solvents such as Dow Corning® brand OS Fluids, naphtha, mineral spirits, or methyl ethyl ketone (MEK). Light surface abrasion is recommended whenever possible, because it promotes good cleaning and increases the surface area for bonding. A final surface wipe with acetone or IPA is also useful to remove residues that may be left behind by other cleaning methods. On some surfaces, different cleaning techniques will give better results than others. Users should determine the best techniques for their applications.
Upon standing, some filler may settle to the bottom of the liquid after several weeks. To ensure a uniform product mix, the material in each container should be thoroughly mixed prior to use. Two-part materials should be mixed in the proper ratio either by weight or volume. The presence of light-colored streaks or marbling indicates inadequate mixing.
Automated airless dispense equipment can be used to reduce or avoid the need to de-air. If de-airing is required to reduce voids in the cured elastomer, consider a vacuum de-air schedule of >28 inches Hg (or a residual pressure of 10-20 mm of Hg) for 10 minutes or until bubbling subsides.
The one-part moisture-cure adhesives are generally cured at room temperature and in a range of 20 to 80 percent relative humidity. Greater than 90 percent of their full physical properties should be attained within 24 to 72 hours depending on the product chosen. These materials are not typically used for highly confined or deep section cures. Materials will generally cure about 0.25 inch (6.35 mm) per 7 days. Addition-cure adhesives should be cured at 100ºC (212ºF) or above. The cure rate is rapidly accelerated with heat (see heat-cure times in Typical Properties table). Thin sections of less than 2 mils may be cured in 15 minutes at 150ºC (302ºF). For thicker sections, a pre-cure at 70ºC (158ºF) may be necessary to reduce voids in the elastomer. Length of pre-cure will depend on section thickness and confinement of adhesive. It is recommended that 30 minutes at 70ºC (158ºF) be used as a starting point for determining necessary pre-cure time. Addition-curing materials contain all the ingredients needed for cure with no by-products from the cure mechanism. Deep-section or confined cures are possible. Cure progresses evenly throughout the material. These adhesives generally have long working times.
Due to the wide variety of substrate types and differences in substrate surface conditions, general statements on adhesion and bond strength are impossible. To ensure maximum bond strength for elastomers and adhesives on a particular substrate, 100 percent cohesive failure of the adhesive in a lap shear or similar adhesive strength is needed. This ensures compatibility of the adhesive with the substrate being considered. Also, this test can be used to determine minimum cure time or to detect the presence of surface contaminants such as mold release agents, oils, greases and oxide films.
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Cure Temperature Test Methods
|Cure Temperature||Cure Time Test Method|
|20 to 25°C|
|100°C||Time to 90 percent of final hardness and adhesion or 90 percent of curve height for elastic modulus additional time may be required for the part to warm to near oven temperature.|
|125°C||Time to 90 percent of final hardness and adhesion or 90 percent of curve height for elastic modulus|
|150°C||additional time may be required for the part to warm to near oven temperature.|
Cure Time Test Methods
|Cure Time||Test Method|
Work / Pot Time Test Methods
|Work / Pot Time||Test Method||Temperature|
|60 min||Time to double initial mixed viscosity||25°C|
Dielectric Constant Test Methods
|Dielectric Constant||Test Method|
|5.20||Dielectric constant, 100 Hz|
|5.20||Dielectric constant, 100 KHz|
Dissipation Factor Test Methods
|Dissipation Factor||Test Method|
|0.00100||Dissipation factor, 100 Hz|
|<0.00010||Dissipation factor, 100 KHz|
Thermal Conductivity Test Methods