DOWSIL 3-6121 | Krayden

Main features

Low-Temperature Use to -65 deg C
275% Cured Elongation
10-Minute 150 deg C Cure

Product Description

DOWSIL™ 3-6121 Low Temperature Elastomer is a two-part, translucent silicone encapsulant supplied at a 10:1 mix ratio for potting and protecting printed circuit board system assemblies. The flowable mixed material heat-cures to a flexible elastomer with a typical Shore A hardness of 34, tensile strength of 4.3 MPa, and elongation of 275%. It retains good properties at temperatures down to -65°C and has a higher refractive index than typical dimethyl silicones, supporting both low-temperature encapsulation and optical applications. Multiple heat-cure schedules allow processing time to be selected according to production temperature.

Key features

Low-temperature performance: Retains good properties at temperatures down to -65°C for cold-environment encapsulation applications.
Flexible cured elastomer: Provides a typical Shore A hardness of 34 with 275% elongation after cure.
Temperature-controlled cure: Typical heat-cure schedules range from 20 minutes at 100°C to 10 minutes at 150°C.
Flowable two-part system: Uses a 10:1 mix ratio and has a typical mixed viscosity of 19,250 mPa·s.
Electrical insulation properties: The cured material has a typical dielectric strength of 18 kV/mm and volume resistivity of 4.15 × 1014 Ω·cm.
Optical application potential: Has a higher refractive index than typical dimethyl silicones.

Applications / Suitable for

Potting and encapsulation of printed circuit board system assemblies
Low-temperature encapsulating applications
Optical applications requiring a higher-refractive-index silicone elastomer

TDS, SDS & Technical Documents

DOWSIL™ 3-6121 Low Temperature Elastomer Technical Data Sheet

English (Technical Data Sheet (TDS))

Technical Specifications

General Properties

Specific Gravity

1.12

Work life @25°C

>2 hours

Electrical Properties

Dielectric Strength

18 kV/mm

Volume Resistivity

4.15E14 Ohms⋅cm

Mechanical Properties

Elongation

275 %

Additional Information

Silicone potting and encapsulation

DOWSIL™ 3-6121 Low Temperature Elastomer

A two-part, translucent silicone encapsulant for potting printed circuit board system assemblies. The 10:1 material is flowable before cure and forms a flexible elastomer that retains good properties at temperatures down to -65°C. Temperature-controlled heat-cure schedules support different production-cycle requirements.

Two-part silicone 10:1 mix ratio Translucent 19,250 mPa·s mixed viscosity Performance down to -65°C

DOWSIL 3-6121 Low Temperature Elastomer two-part product kit

Two-part DOWSIL™ 3-6121 Low Temperature Elastomer for electronic potting and encapsulation.

Before processing

As-supplied properties

Mixed viscosity

19,250 mPa·s

Typical mixed-state value for evaluating dispensing and cavity-filling behavior.

Working time

>2 hours

Typical pot life at 25°C, defined by the time required for the mixed viscosity to double.

Mix ratio

10:1

Two liquid components must be thoroughly mixed before dispensing and cure.

Property	Typical value	Unit	State / condition
Product form	Two-part liquid silicone encapsulant	—	As supplied
Color	Translucent	—	Mixed material
Mix ratio	10:1	—	Two-component system
Part A viscosity	33,475	mPa·s	Part A or base
Mixed viscosity	19,250	mPa·s	After thorough mixing
Working time	>2	hours	Pot life at 25°C

Values shown are typical and are not intended for use as product specifications.

Processing

Mixing, dispensing and curing

Thoroughly mix the two liquid components before dispensing. The mixed encapsulant may be poured or metered directly into the assembly or container in which it will cure. Processing should minimize entrapped air, particularly around assemblies with small or complex voids.

Mixing: Combine the two liquid components at the specified 10:1 ratio and mix thoroughly before application.

Air management: Minimize air entrapment during pouring or dispensing. Vacuum dispensing or post-dispense evacuation may be used when practical.

Heat cure: Typical schedules are 20 minutes at 100°C, 20 minutes at 125°C, or 10 minutes at 150°C.

Post-cure: No post-cure is required; the elastomer may be placed in service after completion of the selected cure schedule.

Illustration of metered mixing and dispensing silicone encapsulant into a printed circuit board enclosure

Recommended processing sequence

Stage 1

Prepare the assembly

Clean the surfaces to be encapsulated. Where adhesion is required, evaluate and apply an appropriate silicone primer according to the primer instructions.

Stage 2

Mix and dispense

Mix both components thoroughly, then pour or use automated metered mixing and dispensing equipment to fill the required cavity.

Stage 3

Remove entrapped air

Use vacuum dispensing or evacuate the filled unit when practical, especially for assemblies containing numerous small voids.

Stage 4

Complete the cure

Apply one of the documented heat-cure schedules and confirm that the material has completed cure before placing the assembly in service.

Storage and compatibility

The typical shelf life is 18 months at 25°C. Store at or below 25°C in tightly closed containers and minimize exposure to moisture. Certain organometallic compounds, sulfur-containing materials, unsaturated hydrocarbon plasticizers, and some solder-flux residues can inhibit cure. Conduct a small-scale compatibility test when a substrate or process material is in question.

After cure

Cured material properties

Typical values describe the cured bulk elastomer and should not be treated as guaranteed specifications or assembly-level performance ratings.

Property	Typical value	Unit	Context
Specific gravity	1.12	—	Cured material
Hardness	34	Shore A	Durometer hardness
Tensile strength	4.3	MPa	Cured elastomer
Elongation	275	%	Cured elastomer
Tear strength	43	N/cm	Die B
Dielectric strength	18	kV/mm	Bulk cured material; not a working-voltage rating
Volume resistivity	4.15 × 1014	Ω·cm	Bulk cured material
Low-temperature property retention	Down to -65	°C	Application performance should be verified in the intended assembly

Supported use contexts

Applications

Printed circuit board assembly being filled with silicone encapsulant inside an electronic enclosure

PCB assembly potting

The product may be poured or metered into electronic enclosures to encapsulate printed circuit board system assemblies. Its flowable mixed state supports cavity dispensing, while the cured silicone provides flexible mechanical protection and bulk electrical-insulation properties.

Electronic assembly undergoing low-temperature environmental evaluation after silicone encapsulation

Low-temperature encapsulation

The elastomer retains good properties at temperatures down to -65°C, making it relevant for assemblies evaluated for cold-temperature exposure. Performance should be confirmed using the intended component geometry, cooling rate, hold time, and temperature history.

Optical electronic assembly encapsulated with a translucent silicone elastomer

Optical encapsulation

The translucent elastomer has a higher refractive index than typical dimethyl silicones and may be considered for optical encapsulation applications in which that material characteristic is relevant. Optical performance must be evaluated in the intended device and geometry.

Product resource

Encapsulants and Gels Selection Guide

Review the Dow encapsulants and gels portfolio by viscosity, hardness, cure profile, and application category. The guide includes DOWSIL™ 3-6121 Low Temperature Elastomer in the standard-encapsulant comparison table and provides broader selection context for silicone encapsulants and gels.

Open the Encapsulants and Gels Selection Guide

Technical support

Evaluate DOWSIL™ 3-6121 for your potting process

Krayden can help review cavity geometry, dispensing requirements, cure schedules, adhesion preparation, material compatibility, low-temperature conditions, and electrical-property requirements for your PCB encapsulation application.

Contact Krayden