RTV Diluent - Silicone Thinner / Thinning Fluid

GENERAL DESCRIPTION: RTV diluent is a water clear, odorless, low viscosity, silicone fluid which was especially designed as a thinner for silicone RTV rubber compounds. It is essentially non-toxic, non-irritating, and non-sensitizing. It has a serviceable temperature range of -40°F to 550°F, and is heat and age stable. It can survive indefinite exposure at temperatures up to 149°C. Because of the extremely low surface tension of this fluid, it aids the flow of the RTV compound and the wet-out of the pattern.

Normally, this thinner is added at a 10% level based on the weight of RTV base being used. At this level, no loss of physical property can be observed. Incidentally, the amount of RTV catalyst is also based on the amount of RTV base being used and does not have to be increased because of the thinner being added. An example of a proper batch would be 10 + 1 + 1, which is 10 oz of RTV base + 1 oz of catalyst + 1 oz of diluent. The room temperature viscosity of this silicone oil is 50 centistokes (cSt).

This thinner, when added, alters the properties of RTV in the following manner:

(1) Reduced Viscosity. RTVs with 10% thinner will show a much lower viscosity, and air release properties will be enhanced. Flowability will also be noticeably improved. This insures that the RTV will get into the detail better.

(2) Increased Chemical Resistance. In some applications, the presence of RTV diluent improves the resistance to chemical attack and thus extends mold life. In fact, some firms make it a practice to wipe additional thinner onto the face of the mold periodically to bolster the release and the life of the mold.

(3) Lower Durometer. In concentrations above 10%, the thinner will begin to plasticize the RTV to produce a cured product that is softer than usual.

(4) Lower Tear Strength. Again, in concentrations above 10%, the thinner will begin to lower the tear strength and the tensile strength, while elongation is increased.


In determining if EP7710 thinner should be incorporated in the RTV system, the above features should be considered. Trials should be made using various percentages of diluent in order to determined the proper levels.

OUTSTANDING CHARACTERISTICS: Inertness; heat stability; oxidation stability; low viscosity; constant thermal conductivity; high compressibility; excellent electrical properties; non-corrosive; highest purity; low pour point; low flammability; chloride-free; narrow and consistent molecular weight distribution. Our silicone fluid is miscible with nonpolar liquids (hydrocarbons, chlorinated hydrocarbons, ethers) and are immiscible with water, alcohols, glycerine and other polar liquids. The only solids that dissolve in our diluent are non-ionic and dissolve only near their melting points. Listed below are some physical properties of our silicone fluid:

Appearance: Clear, colorless
Viscosity at 0°C: 85 centistokes (cSt)
Viscosity at 25°C: 50 centistokes (cSt)
Viscosity at 100°C: 15 centistokes (cSt)
Viscosity at 150°C: 9 centistokes (cSt)
Refractive Index: 1.38 - 1.40
Specific Heat at 25°C 0.36 Btu/lb/°F
Heat of Combustion: approx 11,000 Btu/lb/F
Oxidation Stability at 149°C: Indefinite
Oxidation Stability at 204°C: 1000 hours
Oxidation Stability at 260°C: 200 hours
Thermal Stability in Vacuum: 302°C
Vapor Pressure at 25°C: 0.01 mm Hg
Compressibility (bulk modulus) at 68°C: 1x10¹⁰ dynes/sq cm
Dielectric Strength: 350 volts/mil
Dilectric Constant at 25°C between 10²and 10⁷ cycles: 2.7
Volume Resistivity at 500 Volts and 25°C: 1x10¹⁴

OTHER APPLICATIONS: Some of the other applications include dielectric coolants; brake fluids; lubricants; auto care products; release agents; heat transfer fluid; damping media; antifoam agents; cosmetics; fluid springs; fluid power transmission; fluid springs; precision aircraft instruments and gyros; shock absorbers; electrical insulation; aerosol chemical specialties.

Our silicone fluid is used by vacuum and pressure gauge manufacturers, since it has better insulating properties and vibration response characteristics than glycerin, which is often used. When poured or filled into the gauge, it will help prevent spikes when operators read gauges while loaded.

Much success has been achieved in using this silicone fluid as a lubricant with the following combinations of materials: plastics (polyamides, polystyrenes, phenolics); metals (steel with bronze, brass, chrome, zinc & cadmium, and chrome with bronze). It has no lubricating benefits for Steel on steel contacts.

STORAGE AND SHELF LIFE: EP7710 diluent has an unlimited useful shelf life. It should be stored at room temperature away from heat or open flame.

RTV Diluent is available in the following sizes:

Pint - $14.25
Gallon - $51.84
5 Gallon (40 lb) - $193.60
55 Gallon Drum (440 lbs) - $1760.00

Other silicone oils availble from Eager Plastics (5 Gallon and 55 Gallon Drum Sizes only) include room tempeature viscosities of 20; 100; 350; 1000; 5000; 12500; 30000; and 60000 centistokes.