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Primer selection guide
Specification Writers: Please contact your local Dow sales office or your Global Dow Connection before writing specifications on these products.

A gel can simply be poured into the cleaned repaired area and cured. When repairing an area using an encapsulant, roughen the exposed surfaces of the cured encapsulant with an abrasive paper and rinse with a suitable solvent. 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.
Unit of Measure

Specifications

Flash Point

 N/A –13 (9) ºC–13 (9) ºF

Volatile Organic Content (VOC)

 N/A 681 g/L

Special Properties

 N/A Improves inhibition resistance

For Use On

 N/A Most metals, glass and ceramics

For Use With

 N/A All two-part addition cure

Adhesion

N/A Dow silicone adhesives are specially formulated to provide unprimed adhesion to many reactive metals, ceramics and glass, as well as to selected laminates, resins and plastics. However, good adhesion cannot be expected on non-reactive metal substrates or non-reactive plastic surfaces such as Teflon®, polyethylene or polypropylene. Special surface treatments such as chemical etching or plasma treatment can sometimes provide a reactive surface and promote adhesion to these types of substrates.

Dow brand primers can be used to increase the chemical activity on difficult substrates. For best results, the primer should be applied in a very thin, uniform coating and then wiped off after application. After application, primers should be thoroughly air dried prior to application of the silicone elastomer. Additional instructions for primer usage can be found in the Dow literature, "Dow brand Primers, Prime Coats and Adhesion Promoters” (Form 10-909) and in the information sheets specific to the individual primers. Alternatively, use a low-viscosity primerless adhesive to pot your components.

Poor adhesion can be experienced on plastic or rubber substrates that are highly plasticized since the mobile plasticizers act as release agents. Small-scale laboratory evaluation of all substrates is recommended before production trials are made.

In general, increasing the cure temperature and/or cure time will improve the ultimate adhesion.

Compability

N/A
Certain materials, chemicals, curing agents and plasticizers can inhibit the cure of addition-cure materials. Most notable of these include:

  • Organotin and other organometallic compounds
  • Silicone rubber containing organotin catalyst
  • Sulfur, polysulfones or other sulfur-containing materials
  • Amines, urethanes or amine-containing materials
  • Unsaturated hydrocarbon plasticizers
  • 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.