Technical Data Sheet Description
RTV615, RTV655 and RTV656 silicone rubber compounds are clear liquids which cure at room temperature to high strength silicone rubber with the
addition of curing agents. These two-component products are supplied with curing agent in matched kits which are designed for use at a convenient
These compounds are clear and colorless but differ in low temperature flexibility. All three are low viscosity, easily pourable liquids with nominal
viscosities ranging between 3000 and 7000 cps. RTV655 and RTV656 silicone rubber compounds have the capability of remaining flexible at
RTV615, RTV655 and RTV656 silicone rubber compounds have been used for protection of electronic components and assemblies against shock,
vibration, moisture, ozone, dust, chemicals, and other environmental hazards by potting or encapsulation of the components and assemblies.
The optical clarity of these silicone rubber compounds suggests evaluation for applications such as potting solar cells for maximum light transmission and
electronic assemblies where component identification is necessary or desirable. RTV655 and RTV656 silicone rubber compound are preferred where
flexibility at temperatures down to -115°C (-175°F) is required
Key Features and Benefits
Convenient 10:1 mixing ratio for use in automatic dispensing or hand operations
Low viscosity allows easy flow in and around complex parts, providing excellent electrical insulation and shock resistance
Will cure in deep sections or enclosed assemblies without exotherm and with low shrinkage
Chemical composition contains no solvents for ease of use on production lines
Reversion resistance and hydrolytic stability permit use in high humidity environments at elevated temperatures
Clarity permits visual inspection for easy identification and repair of encapsulated parts
Retention of elastomeric properties at temperatures up to 204°C (400°F)
Typical Physical Properties UNCURED PROPERTIES UNCURED PROPERTIES WITH CURING AGENT ADDED CURED PROPERTIES (Cured 1 hr. @ 100ºC/212ºF) Mechanical Electrical
Dielectric Strength, kv/mm (v/mil) (1.9 mm thick)
Thermal Conductivity, gm-cal/sec, cm2, °C/cm (Btu/hr, ft2, °F/ft)
Coefficient of Expansion, cm/cm, °C (in/in, °F)
Nothing contained herein shall be construed to imply the nonexistence of any relevant patents or to constitute a permission, inducement or
recommendation to practice any invention covered by any patent, without authority from the owner of the patent.
Product Safety, Handling and Storage
RTV615B, RTV655B and RTV656B curing agents can generate flammable hydrogen gas upon contact with acidic, basic, or oxidizing materials. Such
Customers should review the latest Material Safety Data Sheet (MSDS) and label for product safety information, safe handling instructions, personal
protective equipment if necessary, and any special storage conditions required for safety. MSDS are available at www.momentive.com or, upon
request, from any Momentive Performance Materials (MPM) representative. For product storage and handling procedures to maintain the product quality within our stated specifications, please review Certificates of Analysis, which are available in the Order Center. Use of
other materials in conjunction with MPM products (for example, primers) may require additional precautions. Please review and follow the safety
information provided by the manufacturer of such other materials.
Processing Recommendations Compatibility
RTV615, RTV655 and RTV656 silicone rubber compounds will cure in contact with most clean, dry surfaces. However, certain materials, such as butyl
and chlorinated rubber, sulfur-containing materials, amines, and certain metal soap-cured RTV silicone rubber compounds, can cause cure inhibition.
Cure inhibition is characterized by a gummy appearance of the RTV silicone rubber compound at the interface between it and the substrate.
It is recommended that a sample patch test be performed with RTV615, RTV655 and RTV656 silicone rubber compounds to determine if a barrier coating
or other inhibition-preventing measures are necessary before pouring the material.
Select a mixing container 4-5 times larger than the volume of RTV silicone rubber compound to be used. Weigh out ten parts of the A component and one
part of the B component. Since RTV615, RTV655 and RTV656 silicone rubber compounds are kit-matched, work time (or pot life), cure time, and final
properties of the cured RTV silicone rubber compound can be assured only if the A component is used with the B component from the same kit.
With clean tools, thoroughly mix the A and B components together, scraping the sides and bottom of the container carefully to produce a homogeneous
mixture. When using power mixers, avoid excessive speeds which could entrap large amounts of air or cause overheating of the mixture, resulting in
Air entrapped during mixing should be removed to eliminate voids in the cured product. Expose the mixed material to a vacuum of about 25 mm (29 in.) of
mercury. The material will expand, crest, and recede to approximately the original level as the bubbles break. Degassing is usually complete
approximately two minutes after frothing ceases. When using the RTV silicone rubber compound for potting, a deaeration step may be necessary after
pouring to avoid capturing air in complex assemblies.
Automatic equipment designed to meter, mix, deaerate, and dispense two-component RTV silicone rubber compounds will add convenience to continuous
RTV615, RTV655 and RTV656 silicone rubber compounds will cure sufficiently in 24 hours at 25ºC (77ºF) to permit handling. To achieve optimum
properties an elevated temperature cure or a cure time of 7 days at room temperature is required. The table below illustrates the effect of temperature on
Temperature, °C (°F) Cure Time*
Cure times are only approximate. The actual time is affected by the mass of the unit and the time required to reach the desired temperature.
These silicone rubber compounds require a primer to bond to non-silicone surfaces. RTV656 is tested for adhesion and will typically perform when a
very low temperature adhesive/encapsulant is needed. All of these products do require a primer for bonding as stated herein.
Thoroughly clean the substrate with a non-oily solvent such as naphtha or methyl ethyl ketone and allow to dry. Then apply a uniform thin film of SS4155
silicone primer and allow the primer to air dry for one hour or more. Finally, apply freshly catalyzed RTV silicone rubber compound to the primed surface
and cure as recommended. When dry, SS4155 silicone primer exhibits a white haze which will show through RTV615, RTV655 and RTV656 silicone
rubber compounds. If the appearance of the surface to be bonded must be unchanged, SS4120 silicone primer (which dries to an invisible film) may be
used. For more details on priming and adhesion, refer to Momentive Performance Materials data sheet on silicone primers.
Customers must evaluate Momentive Performance Materials products and make their own determination as to fitness of use in their particular
Specifications FDA STATUS
RTV615 silicone rubber compound and SS4120 silicone primer may be used in food contact applications where FDA regulations apply.
For product prices, availability, or order placement, contact our customer service by visiting momentive.com/ContactSilicones.
For literature and technical assistance, visit our website at: www.momentive.com
The information provided herein was believed by Momentive Performance Materials Inc. (collectively with its subsidiaries, “Momentive”) to be accurate at
the time of preparation or prepared from sources believed to be reliable, but it is the responsibility of the user to investigate and understand other
pertinent sources of information, to comply with all laws and procedures applicable to the safe handling and use of the product, and to determine the
suitability of the product for user's intended application or use. All products supplied by Momentive are subject to Momentive’s standard terms and
conditions of sale. MOMENTIVE MAKES NO WARRANTY, EXPRESS OR IMPLIED, CONCERNING THE PRODUCT OR THE MERCHANTABILITY OR FITNESS THEREOF FOR ANY PURPOSE OR CONCERNING THE ACCURACY OF ANY INFORMATION PROVIDED BY MOMENTIVE, except that the
product shall conform to Momentive’s specifications. Nothing contained herein constitutes an offer for the sale of any product.
Momentive and the Momentive logo are trademarks of Momentive Performance Materials Inc.
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