Dow 839 Silicone Adhesive/Sealant

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Description for Dow 839 Silicone Adhesive/Sealant

Silicone adhesive sealant one-part, translucent blue, moisture cure adhesives are generally cured at room temperature, non-flowing, automated or manual needle dispensing systems.

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Application Type	Bond, Seal, Gaskets
1 Part or 2 Part	1-Part
Material Form	Pre-Cure: Paste, Post-Cure: Elastomer
Substrate	Ceramics, Glass, Reactive metals, Plastics, Resins
Industry	Circuit boards, Light Emitting Diodes (LEDs), Smart Meters, E-Mobility Solutions, Smart Home Devices, CRT module, Electrical leads, Electronic equipment, Electronics, LCD module, Modules, PDP module, Power supplies, PWBs
Manufacturer	Dow
Chemistry	Silicone elastomer
Cure Method	RTV, Moisture
Cure Temperature (°C)	20 to 25
Cure Time (min)	2,880
Viscosity (cPs)	Non-flow
Color	Blue, Translucent
High Temperature Resistance (°C)	200
Low Temperature Resistance (°C)	-45, -55
Volume Resistivity (O)	2.5E+14 (ohms/cm)
Extrusion Rate (g/sec)	10,740

Best Practices for Dow 839 Silicone Adhesive/Sealant

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Technical Data for Dow 839 Silicone Adhesive/Sealant

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Overview

Application Type
- Gasketing - Gaskets
- Adhesive - Bond
- Sealant - Seal
1 Part or 2 Part
- 1-Part
Material Form
- Elastomer - Post-Cure: Elastomer
- Paste - Pre-Cure: Paste
Substrate
- Ceramic - Ceramics
- Glass
- Metal - Reactive metals
- Plastic - Plastics, Resins
- Other - Laminates
Industry
- LED (Light-Emitting Diodes) - Light Emitting Diodes (LEDs)
- Smart Meters
- Smart Home Devices
- E-Mobility Solutions
- Electronics - Circuit boards, CRT module, Electrical leads, Electronic equipment, LCD module, Modules, PDP module, Power supplies, PWBs
- Power Supplies
- Industrial - Housings, Yoke
Chemistry
- Silicone - Silicone elastomer
Application Method
- Dispenser - Automated or manual needle dispensing systems
Cure Method
- Moisture / Condensation Cure - Moisture
- RTV (Room Temperature Vulcanization) - RTV
Color
- Translucent - Translucent
- Blue

Specifications

Cure Specs

Cure Temperature (°C)	20 to 25
Cure Time (min)	2,880
Viscosity (cPs)	Non-flow
Tack Free Time (min)	35	Test Method

Bond Strength

Peel Strength (piw)	25.5 (N/cm2)
Shear Strength (psi)	140	Test Method
Tensile Strength (psi)	285

Material Resistance

Environmental Resistance	Environmental resistance
High Temperature Resistance (°C)	200
Low Temperature Resistance (°C)	-45, -55
Moisture/Humidity Resistance	Moisture/humidity resistance

Conductivity

Dissipation Factor	0.00090, <0.00020	Test Method
Dielectric Strength (V/mil)	Good, 480 Durable, 19 (kV/mm)
Dielectric Constant	2.51, 2.49	Test Method
Volume Resistivity (O)	2.5E+14 (ohms/cm)

Hardness

Shore A Hardness	32
Elongation (%)	345
Flexibility	Flexible

Other Properties

Extrusion Rate (g/sec)	10,740
Specific Gravity	1.020
Coefficient of Thermal Expansion (CTE)	300 (Linear (micron/m °C or ppm ))

Business Information

Shelf Life Details	Shelf life is indicated by the “Use Before” date found on the product label. For best results, Dow Corning RTV adhesives should be stored at or below 25°C (77°F). Special precautions must be taken to prevent moisture from contacting these materials. Containers should be kept tightly closed with head or air space minimized. Partially filled containers should be purged with dry air or other gases, such as nitrogen.
Shelf Life Temperature (°F)	<90
Shelf Life Type	from date of manufacture
Shelf Life (mon)	24

Not Good For

Don't Use With	Plastic, rubber

Best Practices for Dow 839 Silicone Adhesive/Sealant

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1. Surface Preparation
  
  All surfaces should be thoroughly cleaned and/or degreased with Dow Corning® brand OS Fluids, naphtha, mineral spirits, methyl ethyl ketone (MEK) or other suitable solvent. Solvents such as acetone or isopropyl alcohol (IPA) do not tend to remove oils well, and any oils remaining on the surface may interfere with adhesion. 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. Some cleaning techniques may provide better results than others
  
  users should determine the best techniques for their particular applications.
2. Mixing
  
  Upon standing, some filler may settle to the bottom of the liquid containers 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 (1:1 or 10:1) either by weight or volume. The presence of light colored streaks or marbling indicates inadequate mixing.
3. Deairing/Degassing
  
  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 for 10 minutes or until bubbling subsides.
Comparable Materials for Dow 839 Silicone Adhesive/Sealant

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Spec Engine^® Results
- 3145 RTV Grey Adhesive/Sealant(Dow)
  Noncorrosive; high tensile strength, elongation, peel and lap shear values, good for high temperature applications; non-flow.
- 3145 RTV Clear Adhesive/Sealant(Dow)
  Noncorrosive; high tensile strength, elongation, peel and lap shear values, contains UV indicator for automated inspection; non-flow.
- Dowsil 838 Silicone Adhesive Sealant(Dow)
  A one-part, white, non-flowing general purpose adhesive with good flame resistance, room temperature cure, high elongation.
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