DOWSIL™ EI-2888 Primerless Silicone Encapsulant Kit

Harmonization Code : 3910.00.00.90 | Silicones in Primary Forms; Others

Main features

Primerless processing for simpler assembly workflows
Optically clear protection for LED and display electronics
Soft silicone encapsulation for environmental and electrical protection

Product Description

DOWSIL™ EI-2888 Primerless Silicone Encapsulant Kit is a two-part, 1:1 mix ratio, optically clear silicone encapsulant designed for potting rigid and flexible printed circuit board assemblies used in LED lighting, high ingress protection luminaires, explosion proof luminaires, and outdoor displays. It provides 2700 mPa.s mixed viscosity, 60 Shore 00 hardness after 21 days at 22°C, and UL 94 HB and UL 746C f1 recognition while supporting room temperature cure or heat-accelerated cure up to 100°C. This makes it a candidate for assemblies requiring optical clarity, electrical insulation, stress relief, and environmental protection, subject to application-specific testing and qualification.

Key features

Primerless silicone encapsulant - self-priming formulation can develop adhesion on many common substrates without a separate primer, with adhesion testing required for each assembly.
Optically clear - supports review for LED lighting and display assemblies where light transmission through the encapsulant matters.
Low mixed viscosity - 2700 mPa.s mixed viscosity supports flow, pour, or needle dispensing into populated assemblies.
Soft cured elastomer - 60 Shore 00 hardness after 21 days at 22°C can help reduce mechanical stress on sensitive components.
Room temperature or heat-accelerated cure - cure can proceed at 25°C or be accelerated with mild heat up to 100°C.
Outdoor-use recognition - UL 746C f1 recognition supports review for outdoor applications involving UV exposure and water immersion.

Applications / Suitable for

This product fits assemblies that require a balance of optical clarity, electrical insulation, soft silicone protection, and process-friendly encapsulation.

LED lighting: Encapsulation of rigid and flexible circuit boards used in indoor and outdoor lighting assemblies.
High ingress protection luminaires: Potting of electronics where environmental exposure, insulation, and primerless processing need to be evaluated together.
Explosion proof luminaires: Encapsulation of luminaire electronics where soft silicone protection and process-controlled cure are part of the design review.
Outdoor displays: Encapsulation of display electronics where optical transmission and outdoor-use recognition are part of qualification review.

Specifications
Additional Information

Technical Specifications

General Properties

Chemistry Type

Silicone

Component System

Component System
Describes the number of components that must be supplied, mixed, or activated before application or cure.

2 - part

Mix Ratio

Mix Ratio
The amount of a constituent divided by the total amount of all other constituents in a mixture

1:1

Pot Life

Pot Life
Pot life is the amount of time it takes for the viscosity of a material to double (or quadruple for lower viscosity materials) in room temperature after a material is mixed.

It is closely related to work life but it is not application dependent, less precise and more of a general indication of how fast a system is going to cure.

130 minutes

Product Type

Product Type
Material category or functional product class.

Primerless Encapsulant

Shelf Life
Shelf Life @ 25°C	365 days

Physical Properties

Viscosity
Mixed Viscosity	2700 mPa.s
Part A	2000 mPa.s
Part B	2300 mPa.s

Appearance
Appearance Appearance Appearance at room temperature.	Clear

Mechanical Properties

Tensile Strength
Tensile Strength Tensile Strength Tensile strength determines the resistance of a material to break under tension and it measures how much elongating load (or tensile stress) it can handle before fracture. To make it simple, it measures how much force we have to apply when pulling apart a material before it breaks.	0.2 MPa

Elongation

Elongation
Elongation is the process of lengthening something.

It is a percentage that measures the initial, unstressed, length compared to the length of the material right before it breaks.

It is commonly referred to as Ultimate Elongation or Tensile Elongation at break.

190 %

Electrical Properties

Dielectric Strength

Dielectric Strength
Dielectric strength is measured in kV per mm and is calculated by the Breakdown voltage divided by the thickness of the tested material.

Those two properties go hand in hand and while Breakdown voltage is always thickness dependent, dielectric strength is a general material property.

As an example, the dielectric strength of Polyimide is 236 kV/mm. If we place 1mm of Polyimide between two electrodes, it will act as an insulator until the voltage between the electrodes reaches 236 kV. At this point it will start acting as a good conductor, causing sparks, potential punctures and current flow.

19 kV/mm

Volume Resistivity

Volume Resistivity
Volume resistivity, also called volume resistance, bulk resistance or bulk resistivity is a thickness dependent measurement of the resistivity of a material perpendicular to the plane of the surface.

10000000000000000 Ohms⋅cm

Thermal Properties

Gel Time
Gel Time @22°C Gel Time @22°C The time at which a liquid polymer or resin begins to form a continuous cross-linked gel network and loses practical flowability under defined test conditions. In rheological measurements, the gel point is the crossover point where the storage modulus G′ equals the loss modulus G′′, indicating the transition from liquid-dominant to solid-like behavior.	8 hours

UL 94 Rating

UL 94 Rating
Flammability rating classification.
It determines how fast a material burns or extinguishes once it is ignited.

HB: slow burning on a horizontal specimen; burning rate less than 76 mm/min for thickness less than 3 mm or burning stops before 100 mm
V-2: burning stops within 30 seconds on a vertical specimen; drips of flaming particles are allowed.
V-1: burning stops within 30 seconds on a vertical specimen; drips of particles allowed as long as they are not inflamed.
V-0: burning stops within 10 seconds on a vertical specimen; drips of particles allowed as long as they are not inflamed.
5VB: burning stops within 60 seconds on a vertical specimen; no drips allowed; plaque specimens may develop a hole.
5VA: burning stops within 60 seconds on a vertical specimen; no drips allowed; plaque specimens may not develop a hole

Curing Conditions

Curing Schedule
Cure Time @100°C	1 - 2 hours
Cure Time @25°C	10 - 12 hours
Cure Time @50°C	6 - 7 hours
Cure Time @80°C	3 - 4 hours

Additional Information

Optically clear silicone encapsulant

DOWSIL™ EI-2888 Primerless Silicone Encapsulant Kit

DOWSIL™ EI-2888 Primerless Silicone Encapsulant Kit is a two-part, 1:1 mix ratio, optically clear, self-priming silicone encapsulant designed for potting rigid and flexible PCB assemblies in LED lighting, high ingress protection luminaires, explosion proof luminaires, and outdoor displays. It provides 2700 mPa.s mixed viscosity and 8 h gel time at 22°C, giving engineers a practical starting point for evaluating optical protection, electrical insulation, stress relief, and environmental exposure requirements.

1:1 mix ratio 2700 mPa.s mixed viscosity 8 h gel time at 22°C 60 Shore 00 after 21 days at 22°C UL 94 HB and UL 746C f1

Technical data sheet SDS Part A SDS Part B Contact us

Review substrate adhesion, cure schedule, optical path, potting depth, and exposure profile before qualification.

LED strip assembly encapsulated with DOWSIL EI-2888 Primerless Silicone Encapsulant

EI-2888 used in LED strip encapsulation

Key features

Optically clear system: 94% light transmission at 450 nm and 95% at 760 nm, measured at 5 mm by ASTM D 1003.
Self-priming adhesion: formulated to develop adhesion to many common substrates without primer, with substrate-specific testing required.
Low mixed viscosity: 2700 mPa.s mixed viscosity can help support pour, flow, and needle dispense processing.
Soft cured profile: 60 Shore 00 after 21 days at 22°C can help support low-stress encapsulation.
Agency recognition: UL 94 HB and UL 746C f1 recognition support review for flame and outdoor-use requirements where applicable.

Processing summary

Mix ratio: Two-part system, 1:1 mix ratio by weight or volume.

Working life: Pot life is 130 min at 22°C. Gel time, measured at G prime = G double prime, is 8 h at 22°C. Values can vary with humidity, temperature, and mixing method.

Cure: Room temperature cure at 25°C or heat-accelerated cure up to 100°C. Mild heat can reduce handling and full-cure time.

Application methods: Automated static or dynamic metered mixing, manual mixing, flow dispense, pour dispense, or needle dispense.

Processing guidance

Mixing, dispensing, and cure considerations

Mixing setup

Mix Part A and Part B thoroughly before dispense. Automated metered mixing can help support ratio control in production, while manual mixing should be evaluated for air entrapment and repeatability.

Void control

Where practical, dispense under vacuum. If vacuum dispensing is not available, evacuate the assembly after dispense, especially when the PCB or housing contains small voids.

Surface preparation

Apply to clean and dry substrates. Low-surface-energy materials, release agents, oils, greases, oxide films, or other contamination can affect adhesion and should be checked during qualification.

Cure review

Adhesion develops during cure and increases toward full cure at room temperature. Confirm handling time, cure time, and minimum acceptable properties on the actual assembly.

Qualification note

General adhesion statements are not possible across all substrates. Use lap shear, peel, or assembly-level testing to confirm adhesion, cure schedule, and compatibility with the intended substrate stack.

Typical properties

Uncured and processing properties

Values are typical and not intended for specification writing. Review the current technical data sheet before qualification.

Property	Typical value	Unit	Test method / condition
System format	Two-part	Not applicable	Per technical data sheet; Part A and Part B
Mix ratio	1:1	Not applicable	By weight or volume
Appearance	Clear	Not applicable	CTM 0176B; uncured material
Viscosity, Part A	2000	mPa.s	CTM 0050; unmixed component
Viscosity, Part B	2300	mPa.s	CTM 0050; unmixed component
Viscosity, mixed	2700	mPa.s	CTM 0050; after mixing Part A and Part B
Gel time at 22°C	8	h	ASTM D 4440; G prime = G double prime at 22°C
Pot life at 22°C	130	min	CTM 0055; can vary with humidity, temperature, and mixing method

Cured mechanical and adhesion properties

Cure basis: room temperature cure at 22°C unless otherwise stated in the property line.

Property	Typical value	Unit	Test method / condition
Durometer after 24 h at 22°C and 50°C	12 to 28	Shore 00	ASTM D 2240; 12 at 22°C and 28 at 50°C
Durometer after 3 days at 22°C	35	Shore 00	ASTM D 2240; room temperature cure
Durometer after 7 days at 22°C	45	Shore 00	ASTM D 2240; room temperature cure
Durometer after 21 days at 22°C	60 / 10	Shore 00 / Shore A	ASTM D 2240; room temperature cure
Tensile strength	0.2	MPa	ASTM D 412; cured elastomer
Elongation	190	%	ASTM D 412; cured elastomer
Unprimed lap shear, aluminum	0.17	MPa	CTM 0243; unprimed aluminum substrate

Electrical, optical, and recognition data

Property	Typical value	Unit	Test method / condition
Dielectric strength	19	kV/mm	CTM 0114; cured material
Volume resistivity	1E+16	Ohm*cm	CTM 0249; cured material
Light transmission at 380 nm, 5 mm	91	%	ASTM D 1003; 5 mm thickness
Light transmission at 450 nm, 5 mm	94	%	ASTM D 1003; 5 mm thickness
Light transmission at 760 nm, 5 mm	95	%	ASTM D 1003; 5 mm thickness
Flammability test	UL 94 HB	Not applicable	UL 94; review current listing before specification
Outdoor use recognition, UV exposure and water immersion	f1	Not applicable	UL 746C; UV exposure and water immersion
Shelf life at 22°C	12	months	Per technical data sheet; at 22°C

Recommended handling time versus curing temperature

Temperature	Time	Basis
25°C	10 to 12 h	Recommended handling time
50°C	6 to 7 h	Recommended handling time
80°C	3 to 4 h	Recommended handling time
100°C	1 to 2 h	Recommended handling time

Storage and handling, per technical data sheet

Special precautions should be taken to keep moisture from contacting the product. Keep containers tightly closed, minimize headspace, and purge partially filled containers with dry air or nitrogen where appropriate. Store in the original packaging with the cover tightly attached and use the product by the Use Before date on the label.

Applications

Where DOWSIL™ EI-2888 fits

LED lighting

Designed for encapsulating rigid and flexible circuit boards used in indoor and outdoor LED lighting where optical clarity and environmental protection are reviewed together.

94% light transmission at 450 nm, measured at 5 mm.
UL 746C f1 recognition supports outdoor-use review.
2700 mPa.s mixed viscosity supports dispensing into LED assemblies.

Review lighting requirements

High ingress protection luminaire electronics prepared for silicone potting

High ingress protection luminaires

Can be evaluated for high ingress protection and explosion proof luminaire assemblies where insulation, soft encapsulation, and primerless processing matter.

19 kV/mm dielectric strength supports insulation review.
1E+16 Ohm*cm volume resistivity supports electrical protection review.
Room temperature or heat-accelerated cure supports process flexibility.

Discuss luminaire design

Outdoor display electronics requiring optically clear encapsulation

Outdoor displays

May be considered for outdoor display electronics where transparent silicone protection, low-stress encapsulation, and outdoor-use recognition are part of qualification.

95% light transmission at 760 nm, measured at 5 mm.
60 Shore 00 cured hardness after 21 days at 22°C.
Flow, pour, or needle dispense methods support process review.

Evaluate display application

Product resources

Review the product in application context

Product proposition video

Review the Dow product proposition video for an overview of how DOWSIL™ EI-2888 is positioned for LED protection and optical performance.

Primerless encapsulant webinar

Review the Dow webinar for additional context on primerless silicone encapsulation in lighting and outdoor display applications.

Package and support

Plan packaging, storage, and application review

Packaging and storage

Multiple packaging sizes are available.
Store in original packaging with the cover tightly attached.
Keep containers tightly closed and minimize headspace.
Use by the Use Before date shown on the product label.

Technical review inputs

Substrate stack and surface condition.
Potting depth, cavity geometry, and optical path.
Dispense method, mix method, and cure constraints.
Operating temperature, humidity, UV, and water exposure profile.

Technical guidance

Tips and troubleshooting

Issue	Recommended action
Voids or air entrapment	Minimize air during mixing and dispensing. Use vacuum dispensing where practical. Evacuate the potted unit after dispense when the assembly has small voids or confined spaces.
Cure variation or slow handling time	Confirm part temperature, ambient humidity, mix quality, and potting depth. Use mild heat up to 100°C when faster handling is needed and the assembly can tolerate it. Validate the selected cure schedule using hardness, adhesion, and assembly-level checks.
Adhesion below target	Clean and dry the substrate before dispense. Check for mold release agents, oils, greases, oxide films, and other surface contaminants. For difficult low-surface-energy surfaces, evaluate priming or surface treatment such as chemical or plasma etching.
Optical performance below target	Review optical path length, material thickness, LED wavelength, and exposure temperature. For exposure at 150°C and above, evaluate optical aging because optical performance may degrade before mechanical properties become unacceptable. Use application-specific optical testing after cure and after environmental aging.
Storage or shelf-life deviation	Keep containers tightly closed and minimize headspace. Purge partially filled containers with dry air or nitrogen where appropriate. Use the material by the Use Before date shown on the label.
Mixing or ratio error	Confirm the 1:1 mix ratio by weight or volume according to the dispensing setup. Use metered mixing for production where ratio repeatability is critical. Check mixed material uniformity before dispensing into qualification assemblies.

Next steps

Review your DOWSIL™ EI-2888 application requirements

To evaluate DOWSIL™ EI-2888 for your assembly, share the substrate stack, potting depth, dispense method, cure limits, optical path, operating temperature range, environmental exposure, and any UL or outdoor-use requirements.