Thermasil

Thermally Conductive-Fire Resistant Silicone

Silicone dielectric potting and encapsulating compounds with high thermal conductivity and excellent fire resistance properties – for electronic and aerospace applications.

THERMASIL – TYPE I , IX
One–part system – ready to use

THERMASIL – TYPE II
Two-part system-low temperature cure

FEATURES

  • High tensile strength
  • High temperature characteristics
  • Fire resistant. Self extinguishing
  • High thermal conductivity
  • Excellent electrical properties

THERMASIL
Description

Thermasil is a specially processed silicone rubber composition, fire-resistant and non-combustible, designed for thermally conductive potting and encapsulating of electronic equipment. Thermasil is solventless, containing 100% reactive material. Cured simply by heating, Thermasil forms a flexible, heat resistant silicone rubber. It will withstand temperatures in excess of 275 °C. Electrical properties are not sacrificed.

Properties of Thermasil

Type I Type II Type IX
Uncured
Color White White White
Viscosity@ 23 °C (cps) 130,000 ± 10% 140,000 ± 10% 200,00± 10%
Sp.Gr @ 25 °C 2.25 2.03 2.25
Shelf Life 6 months 6 months 6 months
Storage 40 °F or lower Room Temp 40 °F or lower
System One-part Two-part One-part
Cured
Physical
Color White White White
Density 2.25 2.03 2.25
Hardness_Dur Shore A 75-85 55-65 75-85
Tensile strenght (psi) 600 600 600
Elongation % > 100 > 100 > 100
Thermal expansion in/in/°F 35 x 10-6 35 x 10-6 35 x 10-6
Thermal Conductivity
BTU-ft/ft2-hr-°F
7 6 7
Operating Temp. Range °C -50 to 250 (Cont) -50 to +250 (Cont) -50 to 250 (Cont)
Brittle Point °C -55 -55 -55
Electrical:
Dielectric Constant
25 °+C @ 1KHz
4.5 4.5 4.5
Dielectric Strength (v/mil)
1 16 sample
490 > 500 490
Volume Resistivity (ohm-cm) 500 V,dc 1 x 1016 1 x 1015 1 x 1016
(spindle 7, 20 rpm, Brookfield HAT)

CURE SCHEDULE
Any one of the following:

Thermasil I/IX Catalyst Conc. Pot Life Cure Time (hrs)
Thermasil II
25°C 70°C 125°C
100 °C – 4 hours 5% Catalyst S> 1 hour 100 °C – 4 hours 15 4 2
125 °C – 1 ½ hours 10% Catalyst S> ½ hour 125 °C – 1 ½ hours 12 2 1
150 °C – 1 hour 5% Catalyst T 3 hours 150 °C – 1 hour 30 6 3

APPLICATIONS:

Thermasil is recommended as a protective coating for electronic components from which heat is to be dissipated and where fire resistance is of prime importance, and also as a “form-in place” heat sink. It is useful as a conformal coating for electronic assemblies which must operate at high temperature and voltage conditions, as well as for power resistors, cables and connectors.

Among the advantages of Thermasil conformal coatings are: protection against corrosion and humidity, Class H insulation, high electrical insulation and stability, mechanical support, and an operating temperature range from -65 °C to + 275 °C. Application is by dipping, painting or potting followed by recommended heat cure.

Thermasil IX, 1 pound kit, corresponds to National Stock Number (NSN) 8030-01-105-8605. Thermasil II, 1 pound kit with Catalyst S, corresponds to National Stock Number 8040-01-105-8604.