Transene - Encapsulants

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 @ 1KH_z	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.