Addition of boron compound to lower burning rate of solid propellant binder is reported. Chemical reactions involved in propellant binder modification are described. Advantages of method for lowering burning rate are analyzed

Thompson, W. W.

English

NASA Technical Reports Server

September 1972	 B72-10560 
NASA TECH BRIEF 
Ames Research Center	
-4r 
NASA Tech Briefs announce new 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. 
Suppressants for Lowering Propellant Binder Burning Rate 
Solid propellants which have a slow rate of burning 
are required for extended space flights. Ordinarily, 
solid propellants burn quite rapidly, but some addi-
tives can be incorporated in propellant compositions 
to moderate the rate of burning. Although a wide 
variety of additives have been tested, very few have 
been found to alter the burning rate significantly. The 
most effective additives known thusfar influence the 
rate of reaction of the oxidizer; small changes in rate 
are magnified because the oxidizer is the major com-
ponent of the propellant system. An attractive possi-
bility for further reduction of propellant burning rate 
lies in modification of the usual binder systems, and 
in a study of propellants prepared with a polyure-
thane binder system and a polyether backbone, it was 
shown that burning rates could be suppressed by a 
phosphorus-containing chain extender and a combi-
nation of phosphorus and boron compounds as plasti-
cizer. However, phosphorus plasticizers are not very 
satisfactory because they are volatile and migrate to 
nonpropellant portions of the rocket engine. 
The chain extender in most polyurethane propel-
lant binders is usually a dthydroxy compound which 
is copolymerized along with the principal hydroxy 
compound in the binder. By substituting a phospho-
rus-containing dihydroxy compound for the usual 
chain extender, a phosphorus moiety is chemically 
bound to the polymer chain of the polyurethane binder 
and thus is not free to migrate. A compound of this
type which has been found suitable is diethyl-N,N-bis 
(2-hydroxyethyl)-aminoethylphosphonate. 
Lower burning rates were also observed when a 
boron compound, trimethoxyboroxene, was used in 
place of a phosphorus plasticizer such as isodecyldi-
phenyl phosphate. Additionally, by combining the 
phosphorus plasticizer with trimethoxyboroxene at a 
total level not exceeding that used for either com-
pound separately, an even lower burning rate was ob-
served; this synergistic effect was unexpected. How-
ever, additional advantages can be realized because 
each component is used at a lower concentration and 
thus their vapor pressures and migration tendencics 
are minimized. 
Note: 
No additional documentation is available. Specific 
questions, however, may be directed to: 
Technology Utilization Officer 
Ames Research Center 
Moffett Field, California 94035 
Reference: B72-10560 
Patent status: 
NASA has decided not to apply for a patent. 
Source: Wallace W. Thompson of 
Rocketdyne/North American Rockwell 
under contract to 
Ames Research Center 
(ARC-10563) 
Category 04 
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.
https://ntrs.nasa.gov/search.jsp?R=19720000559 2020-03-17T03:34:36+00:00Z


Suppressants for lowering propellant binder burning rate

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server