Translastic ® RTV Silicones

Potting and Encapsulation of Electronic Components and Circuit Modules

Translastic ® RTV Silicones cure to a tough flexible silicone rubber which absorbs vibration and provides environmental protection, excellent insulation, resistance to chemical attack and reversion resistance.

RTV 111
White, low viscosity

RTV 141
White, medium viscosity

RTV 130
Red, low viscosity, high strength

RTV 160
Red, medium viscosity, high strength

FEATURES

  • Room temperature or elevated temperature cure
  • Easy mixing, accurate measuring
  • Fast cure, long pot life
  • Excellent electrical protection
  • Vibration damping
  • Meets MIL 23586 requirements

TRANSLASTIC ® RTV SILICONES
DESCRIPTION

Translastic RTV’s are poly-dimethyl siloxane systems which polymerize with the addition of appropriate catalysts. The catalyst initiates a free radical, condensation-type reaction. Reaction rates can be accelerated by heating and/or selection of catalyst. A selection of paste catalysts offer control of cure time and pot life as necessitated by process requirements. In deep or thin section, the polymerization reaction progresses without evolution of exothermic heat and minimal shrinkage.

Translastic RTV’s provide environmental protection against temperature extremes, moisture, contamination, weathering, corona and corrosive atmospheres. RTV materials cure in thin or deep section to form a tough, flexible silicone rubber which absorbs mechanical shock and vibration. The product has many applications including: PC board, conformal coatings, precoating of assemblies before final encapsulation in rigid compounds, insulating motor leads and cable junctions, modules, relays, power supplies, amplifiers, transformers, ferrets, connectors and silicone mold making material.

PROPERTIES OF TRANSLASTIC RTV SILICONES

Type 111 Type 141 Type 130 Type 160
Uncured
Color White White Red Red
Viscosity, cps 10,000 50,000 10,000 35,000
Specific Gravity 1.16 1.30 1.45 1.50
Shelf Life 1 year 1 year 6 months 6 months
Storage Room Temperature or Below
Cured Physical
Self-Extinguishing Yes Yes Yes Yes
Corrosion Resistance
(M-S-23586)
Good/pass Good/pass Good/pass Good/pss
H20 Absorbtion %
(7 day @ 23 °C)
0.4 0.3 0.4 0.2
Durometer 45 45 60 60
Tensile Strength (psi) 375 500 775 850
Elongation (%) 175 175 130 130
Brittle Point (C) -50° -50° -50° -50°
Tear Resistance
(die B lb/in)
15 30 40 40
Operating Temp. (°C) -50° to 250° -50° to 250° -50° to 250° -50° to 250°
Cured Electrical
Dielectrical Strength
(v/mil)
500 500 500 500
Dielectric Constant 3:1 3.2 4 3.8
Diss. Factor 102Hz .004 .01 .007 .003
106Hz .002 .003 .003
Volume Resistivity (23 °C) 1 x 1015 1 x 1014 3 x 1015 2 x 1013
Thermal Conductivity
BTU-ft/ft2-hr-°F
0.17 0.17 0.18 0.18

APPLICATION:

TRANSLASTIC RTV’s and Paste Catalysts S and M are designed for automatic dispensing, mixing and metering for volume applications. Smaller applications readily lend themselves to hand mixing, de-aerating and application by any convenient method such as pouring, dipping or brushing.

A selection of catalyst should be made for the cure. Catalyst S provides a slow cure, Catalyst M cures medium-fast, and Catalyst F provides fast cure. The catalysts are used in approximately 10% concentration.

Curing of Translastic RTV’s may be accomplished at room temperature. A more complete cure may be effected by curing at elevated temperatures, up to 200 °C. Detailed instructions are supplied with each order.

TRANSLASTIC RTV SILICONES

Cured TRANSLASTIC RTV’s offer retention of elastomeric properties from –90 °F to 600 °F, physical toughness and aging, resistance to chemical attack and reversion resistance.

RTV’s 111 and 141 are low to moderate viscosity polymer systems with chemically inert calcium carbonate filler systems. The excellent flow characteristics and deep section cure allow potting of all electronic modules, components, assemblies and relays. Availability in various colors allows for color coding of components.

RTV’s 130 and 160 are low to moderate viscosity polymer systems with a unique iron oxide filler system. Excellent physical properties and high temperature capability allow for encapsulation of transformers, coils and motor windings where elastomeric properties are required up to 600 °F.

Catalyst S, M, F

Three paste catalysts providing non-critical mixing ratios of 10:1 are supplied. The selection of catalyst is based on process requirements for total cure time, pot life and temperature limitations. Catalyst S provides the longest working time; Catalyst M provides shorter pot-life with faster cures. Catalysts S and M may be heat accelerated to provide shorter cure times. Catalyst F offers extremely fast room temperature cures with minimal working time. The Catalyst Performance Charts below provide necessary information for selection.

TABLE I
CATALYST SELECTION FOR TRANSLASTIC RTV SILICONES

Room Temperature Cure – 10% Catalyst Concentration

CATALYST S CATALYST M CATALYST F
RTV
PROD
POT LIFE HRS GEL HRS CURE HRS. POT LIFE HRS GEL HRS CURE HRS. POT LIFE HRS GEL HRS CURE HRS.
111 5 10 30 2 5 25 ¾ 1 ½ 20
141 3 8 20 1 ½ 4 25 ¼ 1 20
130 4 8 20 2 3 15 ½ 1 15
160 5 8 20 2 ½ 4 15 ½ 1 15

Pot life can be extended by refrigeration:
10 hours @ 5 °C; 2 to 4 days @ -10 °C.

TRANSLASTIC RTV SILICONES
TABLE II
CATALYST SELECTION FOR TRANSLASTIC RTV SILICONES

ELEVATED TEMPERATURE CURE – 10% CATALYST CONCENTRATION

CATALYST S CATALYST M
RTV PRODUCT POT LIFE HRS.
25 °C
CURE HRS.
(90 °C)
CURE HRS.
(125 °C)
POT LIFE HRS.
25 °C
CURE HRS.
(90 °C)
CURE HRS.
(125 °C)
111 5 4 2 2 2 1
141 3 ½ 3 1 ½ 1 ½ 1 ½ 1
130 4 3 2 2 2 1
160 5 4 2 ½ 2 1/2 2 ½ 1

APPLICATION

TRANSLASTIC RTV’s and Paste Catalysts S and M are designed for automatic dispensing, mixing and metering for volume applications. Smaller applications readily lend themselves to hand-mixing, deaerating and application by any convenient method –pouring, dipping or brushing.

STEP ONE – Pour RTV into mixing container about ½ full. Add catalyst and mechanically mix or hand-stir thoroughly, keeping entrapment of air to a minimum.

STEP TWO – For complex or densely packed circuit components and/or deep section casting, deaerate under vacuum (20 mm Hg) for 15 minutes.

STEP THREE – Apply by dipping, brushing or pouring. When pouring deep sections, avoid air entrapment. Pouring under vacuum is advisable. Deaerate potting unit after pouring operation. For impregnation of coils or transformers, the deaeration should by followed by application of 10 to 50 psi air pressure.

STEP FOUR – RTV’s cure at room temperature; however, to obtain optimum properties, post-cure heating is necessary. For thick section cures (1/2 ” and greater) best results are obtained utilizing Catalyst S and gellation at room temperature, followed by heating in steps to 25 °C above service temperature of component.

TRANSLASTIC RTV SILICONE rubbers bond to most materials (metal, glass, plastics) with the use of Translastic 13 Organo-Silicone Primer. Simply brush, dip or spray surfaces and allow ½ hour to air-dry before potting component.