Sylgard™ 184 Silicone Elastomer

SYLGARD™ 184 Silicone Elastomer - Transparent encapsulant with good flame resistance

Features and Benefits:

• Flowable
• Room temperature and heat cure
• Good dielectric properties
• Rapid, versatile cure processing controlled by temperature
• High transparency allows easy inspection of components

Composition:

• Two-part
• 10 to 1 mix ratio
• Polydimethylsiloxane elastomer

Applications:

• LED lighting encapsulation
• Power supplies
• Connectors
• Sensors
• Industrial controls
• Transformers
• Amplifiers
• High voltage resistor packs
• Relays
• Adhesive/encapsulant for solar cells
• Adhesive handling beam lead integrated circuits during processing

Typical Properties

Description:

Dow silicone 10 to 1 encapsulants are supplied as two-part liquid component kits. When liquid components are thoroughly mixed, the mixture cures to a flexible elastomer, which is well suited for the protection of electrical/PCB system assembly applications. Dow silicone encapsulants cure without exotherm at a constant rate regardless of sectional thickness or degree of confinement.

Dow silicone elastomers require no post cure and can be placed in service immediately following the completion of the cure schedule. Standard silicone encapsulants require a surface treatment with a primer in addition to good cleaning for adhesion while primerless silicone encapsulants require only good cleaning.

HOW TO USE

Application methods:

• Automated metered mixing and dispensing
• Manual mixing

Substrate Preparation:

• Clean and degrease all surfaces with a suitable solvent prior to potting.
• Note: Make sure that all solvent is removed.

Mixing:

• Sylgard 184 is packaged in lot matched kits with the base and curing agent in separate containers. Mix the two components thoroughly using a weight or volume ratio of 10:1.
• It is recommended to vacuum de-air, with a residual pressure of 10-20 mm mercury, which, when applied for applied for 30 minutes, will sufficiently de-air the material.

How to Apply:

• Apply the encapsulant without entrapping any air. Note: Vacuum encapsulation is recommended for complex geometries.
• For information on appropriate dispensing equipment for your application, please contact Customer Service at 1-800-523-5874.

Curing:

Cure reaction begins with the mixing process. Initially, cure is evidenced by a gradual increase in viscosity, followed by gelation and conversion to a solid elastomer. Pot life is defined as the time required for viscosity to double after base and curing agent are mixed and is highly temperature and application dependent. Please refer to the data table.

Cure using one of the following recommended schedules:

• 15 minutes at 150°C
• 1 hour at 100°C
• 4 hours at 65°C
• 24 hours at 23°C

• Note: Large components and assemblies may require longer curing times.
  Note: At 23°C the material will have cured sufficiently in 24 hours to be handled; however it takes 7 days for full mechanical and electrical properties to be attained.

Temperature Ranges:

For most uses, silicone elastomers should be operational over a temperature range of -45 to 200°C for long periods of time. However, at both the low and high temperature ends of the spectrum, behaviour of the materials and performance in particular applications can become more complex and require additional considerations and should be adequately tested for the particular end-use environment. For low-temperature performance, thermal cycling to conditions such as -55°C (-67°F) may be possible, but performance should be verified for your parts or assemblies. Factors that may influence performance are configuration and stress sensitivity of components, cooling rates and hold times, and prior temperature history. At the high-temperature end, the durability of the cured silicone elastomer is time and temperature dependent. As expected, the higher the temperature, the shorter the time the material will remain useable.

Compatibility:

• In some cases, Sylgard 184 may not cure to optimum properties when in contact with certain plastics or rubbers. Note: Baking the substrate slightly above the cure temperature or cleaning it with solvent will normally eliminate the problem.
• Certain chemicals, curing agents and plasticisers can inhibit a complete cure, including sulfur, polysulfides, polysulfones and other sulfur containing materials; organo-tin compounds; silicone rubber containing organo-tin catalysts; and amines, urethanes, amides and azides.

Repairability:

In the manufacture of electrical devices and PCB system assemblies it is often desirable to salvage or reclaim damaged or defective units. With most non-silicone rigid potting/encapsulating materials, removal or entry is difficult or impossible without causing excessive damage to internal circuitry. Dow silicone encapsulants can be selectively removed with relative ease, depending on the chosen remove method and technique and repairs or changes accomplished, and the repaired area repotted in place with additional product. 

To remove silicone elastomers, simply cut with a sharp blade or knife and tear and remove unwanted material from the area to be repaired. Sections of the adhered elastomer are best removed from substrates and circuitry by mechanical action such as scraping or rubbing and can be assisted by applying DOWSIL™ OS fluids to swell the elastomer. Before applying additional encapsulant to a repaired device, roughen the exposed surfaces of the cured encapsulant with an abrasive paper and rinse with a suitable solvent and dry. This will enhance adhesion and permit the repaired material to become an integral matrix with the existing encapsulant. Silicone prime coats are not recommended for adhering products to themselves.

Handling Precautions:

PRODUCT SAFETY INFORMATION REQUIRED FOR SAFE USE IS NOT INCLUDED IN THIS DOCUMENT. BEFORE HANDLING, READ PRODUCT AND SAFETY DATA SHEETS AND CONTAINER LABELS FOR SAFE USE, PHYSICAL AND HEALTH HAZARD INFORMATION. THE SAFETY DATA SHEET IS AVAILABLE ON THE DOW WEBSITE AT DOW.COM, OR FROM YOUR DOW SALES APPLICATION ENGINEER, OR DISTRIBUTOR, OR BY CALLING DOW CUSTOMER SERVICE.

Usable Life and Storage:

Shelf life is indicated by the “Use Before” date found on the product label. Refer to the product label for storage temperature requirements. Special precautions must be taken to prevent moisture from contacting these materials. Containers should be kept tightly closed and head or air space minimised. Partially filled containers should be purged with dry air or other gases, such as nitrogen.

Disposal Considerations:

Dispose in accordance with all local, state (provincial) and federal regulations. Empty containers may contain hazardous residues. This material and its container must be disposed in a safe and legal manner.

It is the user’s responsibility to verify that treatment and disposal procedures comply with local, state (provincial) and federal regulations. Contact your Dow Technical Representative

for more information.

Note: This product is neither tested nor represented as suitable for medical or pharmaceutical uses.