Dow Dowsil 838 Silicone Adhesive Sealant Datasheet Dow Dowsil 838 Silicone Adhesive Sealant

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  • Description for Dow Dowsil 838 Silicone Adhesive Sealant

    A one-part, white, non-flowing general purpose adhesive with good flame resistance, room temperature cure, high elongation.

    *See Terms of Use Below

    Brand Dowsil
    Application Type Bond, Sealant
    1 Part or 2 Part 1-Part
    Material Form Pre-Cure: Paste, Post-Cure: Elastomer
    Substrate Ceramics, Glass, Many reactive metals, Plastics, Resins
    Industry Circuit boards, Light Emitting Diodes (LEDs), General purpose, PCB, Smart Meters, E-Mobility Solutions, Smart Home Devices, Power Tools, CRT module, Sealing in and around electrical leads, Electronic equipment, Electronics, LCD module, Sealing openings in modules, PDP module, Power supplies, PWBs
    Manufacturer Dow
    Chemistry Silicone elastomer
    Cure Method RTV, Moisture cure, Heat Cure, Room temperature cure
    Cure Temperature (°C) 20 to 25 Room temperature, 25, <60
    Cure Time (min) 2,880, 1,440 to 4,320
    Viscosity (cPs) Non-flowing
    Color White
    High Temperature Resistance (°C) 200
    Low Temperature Resistance (°C) -45, -55
    Volume Resistivity (O) 2.2E+15 (ohms/cm)
    Extrusion Rate (g/sec) 11,952
    Key Specifications UL (Underwriters Laboratory), ULC (Underwriters Laboratories of Canada), NFPA (National Fire Protection Association): UL 94HB
  • Technical Data for Dow Dowsil 838 Silicone Adhesive Sealant

    Overview
    • Application Type
    • 1 Part or 2 Part
      • 1-Part
    • Material Form
      • Elastomer - Post-Cure: Elastomer
      • Paste - Pre-Cure: Paste
    • Substrate
    • Industry
      • LED (Light-Emitting Diodes) - Light Emitting Diodes (LEDs)
      • Smart Meters
      • Smart Home Devices
      • E-Mobility Solutions
      • Electronics - Circuit boards, CRT module, Sealing in and around electrical leads, Electronic equipment, LCD module, Sealing openings in modules, PDP module, Power supplies, PWBs
      • Printed Circuit Board (PCB) - PCB
      • Industrial - Sealing openings in housings, Yoke assembly
      • General Purpose
      • Power Tools
      • Other - Sealing in and around wired
    • Chemistry
    • Application Method
      • Dispenser - Automated or manual needle dispensing systems
    • Cure Method
      • Room Temperature / Air Dry - Room temperature cure
      • Moisture / Condensation Cure - Moisture cure
      • Heat - Heat Cure
      • RTV (Room Temperature Vulcanization) - RTV
    • Color
      • White
    • Key Specifications
      • UL (Underwriters Laboratory), ULC (Underwriters Laboratories of Canada), NFPA (National Fire Protection Association) : UL 94 HB - UL 94HB
    • Brand
      • Dowsil
    Specifications
    Cure Specs
    Cure Temperature (°C) 20 to 25 Room temperature, 25, <60 Test Method
    Cure Time (min) 2,880, 1,440 to 4,320 Test Method
    Viscosity (cPs) Non-flowing
    Fixture or Handling Strength Time (min) 10 to 120
    Tack Free Time (min) 46 Test Method
    Work / Pot Time (min) 60
    Bond Strength
    Shear Strength (psi) 140 Test Method
    Tensile Strength (psi) 270 Test Method
    Material Resistance
    Flame Resistance Good
    Environmental Resistance Environmental resistance
    High Temperature Resistance (°C) 200
    Low Temperature Resistance (°C) -45, -55
    Moisture/Humidity Resistance Moisture resistance, Humidity resistance
    Conductivity
    Dissipation Factor 0.00060, <0.00020 Test Method
    Dielectric Strength (V/mil) Good, Durable, 500
    Dielectric Constant 2.64, 2.63 Test Method
    Volume Resistivity (O) 2.2E+15 (ohms/cm)
    Hardness
    Shore A Hardness 31 Test Method
    Elongation (%) 430, High
    Flexibility Flexible
    Modulus (psi) 60 Test Method
    Other Properties
    Extrusion Rate (g/sec) 11,952
    Specific Gravity 1.020 Test Method
    Coefficient of Thermal Expansion (CTE) 375 (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., DOWSIL 838 Silicone Adhesive Sealant should be stored at or below at or below room temperature (away from direct sunlight), maximum 25°C (77°F) in original, unopened containers.; 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, 77
    Shelf Life Type from date of manufacture
    Shelf Life (mon) 24
    Not Good For
    Don't Use For Polypropylene, Teflon®, Polyethylene
    Don't Use With Non-reactive plastic, Rubber substrates that are highly plasticized, Non-reactive metal, Plastic substrates that are highly plasticized,
  • Best Practices for Dow Dowsil 838 Silicone Adhesive Sealant

    *See Terms of Use Below

    1. Surface Preparation

      Preparing Surfaces All surfaces should be thoroughly cleaned and/or degreased with Dow 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. Testing

      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 on a particular substrate, 100 percent cohesive failure of the adhesive in a lap shear or similar adhesive strength test is desired. This ensures compatibility of the adhesive with the substrate being considered. Also, this test can be used to determine minimum cure time or can 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 Room temperature
25°C
<60°C Mild heat
Cure Time Test Methods
Cure Time Test Method
2,880 min
1,440 to 4,320 min
Tack Free Time Test Methods
Tack Free Time Tack Free Temperature Test Method
46 min 25°C Specification Writers: These values are not intended for use in preparing specifications.
Tensile Strength Test Methods
Tensile Strength Test Method
270 psi Specification Writers: These values are not intended for use in preparing specifications.
Shear Strength Test Methods
Shear Strength Type
140 psi Lap shear strength
Dielectric Constant Test Methods
Dielectric Constant Test Method
2.64 100 Hz
2.63 100 kHz
Dissipation Factor Test Methods
Dissipation Factor Test Method
0.00060 100 Hz
<0.00020 100 kHz
Modulus Test Methods
Modulus Test Method
60 psi Tensile, Specification Writers: These values are not intended for use in preparing specifications.
Shore A Hardness Test Methods
Shore A Hardness Shore Hardness Test Method
31 Durometer, Specification Writers: These values are not intended for use in preparing specifications.
Specific Gravity Test Methods
Specific Gravity Test Method
1.020 Cured, Specification Writers: These values are not intended for use in preparing specifications.