1. Mixing

The mixing ratio of Part A and Part B is 10:1 by weight. The two components are thoroughly mixed using an electrical or pneumatic mixer, on a low speed setting so as to limit the inclusion of air in the mixture. A dispensing machine can also be used.

2. Degasing

After mixing A and B parts, it is preferable to degas the product to eliminate the air bubbles that would be visible in the finished part and which would reduce the

Mechanical and dielectric properties. Degasing is generally carried out with a vacuum of 30 to 50 mbar releasing the vacuum several times during the operation. A recipient with a high diameter/height ratio is better suited to quick degasing; however the height must be sufficient to contain the swelling of the elastomer under vacuum conditions.

3. BLUESIL ESA 7255 50 A&B is poured slowly and regularly. In the case of a high thickness coating operation, the casting must be made at the lowest point in the volume to be filled; this avoids forming and including air bubbles in the volume. It should not be filled totally to allow expansion of the BLUESIL ESA 7255 50 A&B at service temperatures. 

4. For LED process, we recommend pre-heating the PPA substrate at 150°C×1hr to avoid moisture, then curing at the condition: 3 hrs at 150°C.

Certain materials that BLUESIL ESA 7255 50 A&B may be in contact with when curing could inhibit the reaction. Especially troublesome materials are: sulphur-containing cured natural and synthetic rubber compounds (neoprene, latex, SBR), tin catalyzed silicone rubbers, amine catalyzed epoxies, and PVC stabilized with tin salts and some polyurethane elastomers.

BLUESIL ESA 7255 50 A may be stored at a temperature between -20 °C/ -4 °F and 30 °C/ 86 °F for up to 6 months from its date of manufacturing.Please consult the Safety Data Sheet of this product.


BLUESIL ESA 7255 50 A&B is a two component, addition cure, optically clear silicone elastomer.

Optical Encapsulant;Optical Transparency;Protection;UV resistant

2 Part RTV


  • Optical clear
  • High strength silicone elastomer
  • Easy for operation

Particularly suited for LED’s encapsulation.

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