Class of polyphosphazene polymers can be cured at moderate temperatures by action of moisture. In addition, polymers maintain flexibility when exposed to low temperatures

Gerber, A. H.

Reynard, K. A.

English

NASA Technical Reports Server

April 1975	 B75-10038 
NASA TECH BRIEF 
Marshall Space Flight Center 
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Curable Polyphosphazenes 
.
The problem: 
Most organic polymers are usable only over a 
limited temperature range. Most lose their flexibility 
at low temperatures, and many decompose at high 
temperatures. Instability at high temperatures is a 
particular problem because many polymers must be 
cured at 150° C or higher. 
The solution: 
A class of polyphosphazene polymers has been 
developed which can be cured at moderate tempera-
tures by the action of moisture. In addition, the 
polymers maintain flexibility when exposed to low 
temperatures. 
How it's done: 
Polyphosphazenes are inorganic polymers in which 
carbon backbone is replaced by alternating atoms of 
phosphorus and nitrogen, forming linear chains to 
which various groups can be attached. At least some 
of the groups must contain OH functionality. 
Basically, linear phosphazenes are used in which 
the skeletal chains comprise randomly repeating units 
represented by the general formulas: 
r OR 
P=N1:and
	
P=N1 
[OR in
	
. LOW J 
Here the R's are the same or different monovalent 
radicals, such as alkyls, substituted alkyls, fluoro-
alkyls, aryls, substituted aryls, or arylalkyls. R' is a 
monovalent aliphatic or aromatic group or substituted 
alkyl or aryl group containing a functional OH group 
and is represented by the formula 
H 
—Q—C—R"
OH 
Q is either (CH 2 n or C 6H4X(CH 2 m. The X(CH2)m 
group may be meta or para, n is an integer from 1 to 
6, and m is an integer from 1 t 3. The X is 0 (oxygen) 
or CH2 ; R is H or a lower alkyl group with up to 4 
carbon atoms. The ratio of R':R is between 0.5 to 99.5 
and 35 to 65, and n is an integer from 10 to about 
50,000. 
In general, the polyphosphazenes are reacted with 
an excess of polyfunctional isocyanate producing a 
soluble product which cures at moderate tempera-
tures in the presence of moisture. The ratio of 
NCO/OH essential to achieve this result depends on 
the reactivity of the isocyanate and is usually above 
1.5. The resulting isocyanate-terminated prepolymers 
react readily with moisture present in the air at room 
temperatures. The —NCO group is converted to an 
—NH—COOH group which decarboxylates to an 
active —NH 2
 group suitable for crosslinking. 
(continued overleaf) 
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to 
Note: 
Requests for further information may be directed 
to:
Technology Utilization Officer 
Marshall Space Flight Center 
Code ATO1 
Marshall Space Flight Center, Alabama 35812 
Reference: B75-10038
Patent status: 
Inquiries concerning rights for the commercial use 
of this invention should be addressed to: 
Patent Counsel 
Marshall Space Flight Center 
Code CCO1 
Marshall Space Flight Center, Alabama 35812 
Source: K. A. Reynard and A. H. Gerber of 
Horizons Research, Inc. 
under contract to
Marshall Space Flight Center
(MFS-23 134)
C 
is 
B75-10038	 Category: 04 (Materials)


Curable polyphosphazenes

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