Filled polytrifluorochloroethylene /PTFCE/ shows better thermal stability, less creep, and higher compressive moduli than filled polytetrafluoroethylene /PTFE/. Bearing and seal materials exhibiting the best characteristics contain a high percentage of PTFCE

Johnson, R. L.

Wisander, D. W.

English

NASA Technical Reports Server

October 1970	 Brief 70-10573 
NASA TECH BRIEF 
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 Clearinghouse for Federal Scientific and Technical 
Information, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Division, NASA, Code UT, Washington, D.C. 20546. 
Filled Polymers for Bearings and Seals Used in Liquid Hydrogen 
The use of fillers has resulted in reduced wear rate 
and improved mechanical properties (compressive 
modulus and shear strength) of polymers for use in 
liquid hydrogen. The best results were obtained with 
compositions containing 60% graphite and 40% nylon; 
15% Al 2 0 3
 and 85% PTFCE (polytrifluorochloro-
ethylene); and 15 and 25% glass fiber in PTFCE. 
The relatively poor lubricating properties of liquid 
hydrogen require that surfaces in sliding contact 
in the presence of liquid hydrogen be self-lubricating. 
The bearings and seals of liquid-hydrogen turbo-
pumps require materials that will operate for long 
periods of time under severe conditions of load and 
speed. PTFE (poly tetrafluoroethylene), as a base 
material, has been used with success for bearing and 
seal materials in liquid hydrogen. PTFE, however, 
tends to exhibit cold flow under pressure, and also 
has a large coefficient of thermal contraction. To 
minimize these undesirable characteristics, new ma-
terial combinations were needed. 
Friction and wear experiments were performed on 
nine selected polymers with various fillers, to deter-
mine: (I) whether the polymer materials had good 
lubricating properties; (2) whether they had me-
chanical properties better than PTFE for sliding con-
tact in liquid hydrogen; and (3) the effect of fillers 
on these properties. The results of the tests were com-
pared with a reference material, filled PTFE (80% 
PTFE + 15% glass fiber + 5% graphite). 
Friction of most of the polymers was similar to 
that of the PTFE. A comparison ' of the physical prop-
erties of four of the PTFCE's (those filled with 15 
and 25% graphite, and with 15 and 25% glass fiber) 
with the reference material, showed that the filled 
PTFCE's have higher compressive moduli (factors of 
4 to 7), and lower coefficients of thermal contraction 
(factors from one-fourth to two-thirds). 
Although the filled polymers tested did not have 
lower friction or wear, they all showed better thermal 
stability, less creep, and higher compressive moduli 
than filled PTFE. 
Note: 
The following documentation may be obtained 
Irom:
Clearinghouse for Federal Scientific 
and Technical Information 
Springfield, Virginia 22151 
Single document.price $3.00 
(or microfiche $0.65) 
Reference: 
NASA-TN-D-5073 (N69-19800), Friction 
and Wear of Nine Selected Polymers with 
Various Fillers in Liquid Hydrogen 
Patent status: 
No patent action is contemplated by NASA. 
• Source: D. W. Wisander and R. L. Johnson 
Lewis Research Center 
(LEW- 10887) 
Category 04, 07 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned.rights.
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Filled polymers for bearings and seals used in liquid hydrogen

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