Brand Dowsil Application Type Coating, Potting, Encapsulating 1 Part or 2 Part 2 Part Material Form Gel Industry Optoelectronics, Automotive application, Various PCB system assembly application, Smart Meters, E-Mobility Solutions, Smart Home Devices Manufacturer Dow Chemistry Silicone Cure Method 2-Part Cure, Heat, Room Temperature Cure Temperature (°C) 100, 125, 150 Cure Time (min) 35, 12, 7 Color Translucent green, Translucent green High Temperature Resistance (°C) 200 Low Temperature Resistance (°C) -45, -55 Durability Tough Light Refractive Index (RI) High
Technical Data for Dow Dowsil 3-4237 Dielectric Firm Gel
1 Part or 2 Part
- 1 Part or 2 Part - 2 Part
- Dispenser - Automated dispensing equipment
- Room Temperature / Air Dry - Room Temperature
- 2-Part Cure
- Translucent - Translucent green
- Green - Translucent green
Cure Temperature (°C) 100, 125, 150 Test Method Cure Time (min) 35, 12, 7 Test Method Work / Pot Time (min) Long, 12,960 Test Method Mix Ratio 1:1, 1:1 (by volume)
Peel Strength (piw) 3 (ppi) Test Method
High Temperature Resistance (°C) 200 Low Temperature Resistance (°C) -45, -55 Moisture/Humidity Resistance Moisture/humidity resistance
Dissipation Factor 0.00200, 0.00007 Test Method Dielectric Strength (V/mil) Excellent, 475 Dielectric Constant 2.96, 2.96 Test Method Volume Resistivity (O) 9E+14 (ohm*cm)
Durability Tough Shore OO Hardness 25 Flexibility Firm, Resilient, Flexible
Light Refractive Index (RI) High Specific Gravity 0.980 Test Method Coefficient of Thermal Expansion (CTE) 325 (ppm/°C) Test Method
Shelf Life Details Storage conditions and shelf life (“Use By” date) are indicated on the product label. Shelf Life Type from date of manufacture Shelf Life (mon) 12
Not Good For
Don't Use For Some solder flux residues, Organotin compounds, Unsaturated hydrocarbon plasitcizers, Organometallic compounds, Silicone rubber containing organotin catalyst, Sulfur, Polysulfides, Polysulfones, Other sulfur containing materials
Best Practices for Dow Dowsil 3-4237 Dielectric Firm Gel
Some gels are supplied in bladder packs that avoid direct air contact with the liquid gel components, allowing use of air pressure over the pack in a pressure pot for dispensing. Do not apply air pressure directly to the liquid gel surface (without the bladder pack) as the gel can become supersaturated with air and bubbling can occur when the material is dispensed and cured. Use of bladder packs prevents bubbling, maintains cleanliness and avoids gel contamination. Gels can be dispensed manually or by using one of the available types of meter mix equipment. Typically, the two components are of matched viscosities and are readily mixed with static or dynamic mixers, with automated meter-mix normally used for high volume processes. For low-volume applications, manual weighing and simple hand mixing may be appropriate. Inaccurate proportioning or inadequate mixing may cause localized or widespread problems affecting the gel properties or cure characteristics.
If possible, the potential for entrapment and incorporation of gas (typically air) should be considered during design of the part and selection of a process to mix and dispense the gel. This is especially important with higherviscosity and faster-curing gels. Degassing at > 28 inches (10–20 mm) Hg vacuum may be necessary to ensure a void-free, protective layer.
Working time (or pot life) is the time required for the initial mixed viscosity to double at room temperature (RT).
The cure reaction begins when Parts A and B are mixed. As the cure progresses, viscosity increases until the material becomes a soft gel. Cure conditions are shown in the typical properties table. Cure is defined as the time required for a specific gel to reach 90% of its final properties. Gels will reach a no-flow state prior to full cure. Addition-cure silicone gels may be room temperature and heat cure or exclusively heat cure. Adding heat accelerates the cure reaction. Additional time should be allowed for heating the part to near oven temperature. Cure schedules should be verified in each new application.
Certain materials, chemicals, curing agents and plasticizers can inhibit the cure of addition cure gels. Most notable of these include: organotin and other organometallic compounds, silicone rubber containing organotin catalyst, sulfur, polysulfides, polysulfones or other sulfur containing materials, unsaturated hydrocarbon plasticizers, and some solder flux residues. If a substrate or material is questionable with respect to potentially causing inhibition of cure, it is recommended that a small scale compatibility test be run to ascertain suitability in a given application. The presence of liquid or uncured product at the interface between the questionable substrate and the cured gel indicates incompatibility and inhibition of cure.
If a substrate or material is questionable with respect to potentially causing inhibition of cure, a small-scale compatibility test should be run to ascertain suitability in a given application. The presence of liquid or uncured product at the interface between the questionable substrate and the cured gel indicates incompatibility and inhibition of cure. In certain situations, toughened gels may appear fully cured but have reduced or no adhesion. This may result from slight inhibition at the interface.
Comparable Materials for Dow Dowsil 3-4237 Dielectric Firm Gel
Spec Engine® Results
Questions about this material?
Get personal assistance with your specific application needs.
Using LOCTITE® 454™ is a Valid Option for Engineers Working with a Wide Variety of MaterialsRead Article
Sylgard 184 by DOW is the Top Choice for a Transparent, Silicone Encapsulant. Read Why:Read Article
Cure Temperature Test Methods
|Cure Temperature||Cure Time Test Method|
Cure Time Test Methods
|Cure Time||Test Method|
|35 min||Heat Cure|
|12 min||Heat Cure|
|7 min||Heat Cure|
Work / Pot Time Test Methods
|Work / Pot Time||Test Method||Temperature|
|12,960 min||Time to double initial viscosity initial mixed viscosity for two-part products at room temperature. This property is sometimes referred to as pot life.||20 to 25°C|
Peel Strength Test Methods
|Peel Strength||Type||Test Method|
|3 (ppi)||180 Degree Peel Strength||Unprimed Adhesion|
Dielectric Constant Test Methods
|Dielectric Constant||Test Method|
Dissipation Factor Test Methods
|Dissipation Factor||Test Method|
Coefficient of Thermal Expansion (CTE) Test Methods
|Coefficient of Thermal Expansion (CTE)||CTE Test Method|
|325 (ppm/°C)||Linear CTE (by TMA)|
Specific Gravity Test Methods
|Specific Gravity||Test Method|