How to use

Application Methods

• Automatic mixing and dispensing dosing
• Manual mixing

Mixing and venting

The 10 to 1 mix ratio in which these products are supplied gives you one leeway to tailor modulus and hardness to your specific application and production line needs. Venting is not required in most cases.

Substrate preparation

In applications requiring adhesion, priming will be required for many silicone casings. For best results, the primer should be applied in a very thin, uniform layer and then wiped off after application. Once applied, it must be thoroughly cured before applying the silicone elastomer.

Processing / Curing

The thoroughly mixed Dow silicone capsule can be poured/dispensed directly into the container where it is to be cured. Where possible, pouring/dispensing should be done under vacuum, especially if the poured or encapsulated component has many small voids. If this technique cannot be used, the device should be emptied after pouring/dispensing the silicone capsule. Dow silicone casings can be cured at room temperature (25°C/77°F) or heat cured. Room temperature curing encapsulants can also be heat accelerated for faster curing.

Lifetime and curing speed

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

Useful temperature ranges

For most applications, silicone elastomers should operate in a temperature range of -45 to 200°C (-49 to 392°F) for long periods of time. However, at the ends of the spectrum, they should be properly tested for the specific end-use environment. For low temperature performance, thermal cycling to conditions such as -55°C (-67°F) may be possible, but performance of parts or assemblies should be verified.

Compatibility

Certain materials, chemicals, hardeners, and plasticizers may inhibit the curing of addition-curing gels. The most important are: organotin and other organometallic compounds, silicone rubber containing an organotin catalyst, sulphur, polysulfides, polysulphones or other sulfur-containing materials, unsaturated hydrocarbon plasticizers and some solder flux residues. If the substrate or material is in doubt as to its potential to inhibit curing, a small scale compatibility test is recommended to determine suitability for the application. The presence of a liquid or uncured product at the interface between the questionable substrate and the cured gel indicates non-compliance.

Repair and removal

In the manufacture of electrical devices and PCB layout assemblies, it is often desirable to salvage or salvage damaged or defective units.
Dow silicone capsules can be selectively removed with relative ease. To remove silicone elastomers, simply cut with a sharp blade or knife and peel away and remove unwanted material from the area to be repaired. Sections of adhered elastomer are best removed from substrates and circuits by mechanical means such as scraping or rubbing and can be helped by using DOWSIL™ OS Fluids to swell the elastomer.