Two fluorosilicone rubber formulations have been produced which are nonflammable or self-extinguishing. Extensive report was prepared which includes information on testing and describes many alternate formulations

Lieberman, S. L.

English

NASA Technical Reports Server

March 1973	 B73-10102 
NASA TECH BRIEF 
•	 Lyndon B. Johnson Space Center 
NASA Tech Briefs announce now technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Nonflammable Potting-Encapsulating 
and Conformal Coating Compounds 
C 
.
The problem: 
Most nonflammable potting and encapsulating com-
pounds will burn in an oxygen atmosphere or under 
higher than normal oxygen partial pressure. Circuits 
used in high-oxygen environments require a new potting 
compound if they are to be nonflammable. 
The solution: 
Two fluorosiicone rubber formulations have been 
produced which are nonflammable or self-extinguishing in 
environments of up to 11.4 x 10 4
 N/rn2 (16.5 psi) of 
oxygen. 
How it's done: 
The first of the two formulations is designated F-387 
and is a room-temperature-vulcanizing fluorosilicone 
polymer. It consists primarily of two commercially 
available polymers. One of these constituents, a pro-
prietary dimethylsilicone rubber formulation containing 
carbon black, is a common existing encapsulating resin. 
Its basic structure	 1_ 
The incorporated fluorine atoms improve the thermal 
properties of the compound. The other main con-
stituent of F-387 is a commercially available form of 
perchloropentanacyclodecane that is added for its flame 
resistant properties. The resulting mixture is low-tem-
perature curing, highly flame resistant, and has an 
insulation resistance greater than 5 x 108 ohms. 
The second formulation, F-109a, is a modification 
of a proprietary, conventional fluorocarbon polymer
and cures at a temperature which, although higher than 
the first compound, is low enough to allow curing with-
out damaging electronic components (65° C, 150° F). 
The formulation is modified by the addition of boric 
acid to improve the viscosity and MgO and CaO to 
enhance the flame resistance. Also, tetraethylene penta- 
mine, a solvent commonly used in the production of 
silicone rubbers, is added. 
Note: 
As part of the work done on these compounds, an 
extensive report was prepared. It includes much infor-
mation on testing, and describes many alternate formu-
lations. This documentation may be obtained from 
National Technical Information Service 
Springfield, Virginia 22151 
Single document price $6.00 
(or microfiche $0.95) 
Reference: NASA CR. l 15364 (N72-17533) 
Development of Organic Non-Flammable Space-
craft Potting, Encapsulating, and Conformal 
Coating Compounds. 
Patent status: 
Inquiries concerning rights for the commercial use of 
this invention should be addressed to: 
Patent Counsel 
Lyndon B. Johnson Space Center 
Code AM 
Houston, Texas 77058 
Source: S. L. Lieberman of

Furane Plastics, Inc. 
under contract to
Johnson Space Center
(MSC-14164,14166) 
Category 04, 01 
This document was prepared under the sponsorship of the National 	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States 	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States 	 will be free from privately owned rights. 
a
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Nonflammable potting-encapsulating and conformal coating compounds

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