Thin allyl amine polymer films were developed using plasma polymerization. Resulting dry composite membranes effectively reject sodium chloride during reverse osmosis. Films are 98% sodium chloride rejective, and 46% urea rejective

Hollahan, J. R.

Wydeven, T.

English

NASA Technical Reports Server

December 1972
	 B72-10710 
NASA-TECH BRIEF 
Ames Research Center 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
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Reverse-Osmosis Membranes by Plasma Polymerization 
Thin polymer films of allyl amine can be formed 
on microporous filters by polymerization in a radio-
frequency electrodeless plasma; the films have been 
found to provide dry composite membranes which 
are very effective in reverse-osmosis processes. For 
example, a thin film formed on a porous filter substrate 
by plasma polymerization in a high-frequency dis-
charge (13.56 MHz) at about 18 N/rn 2
 (0.1 torr) ex-
hibits as much as 98 percent sodium chloride rejection; 
furthermore, the film also exhibits a 46-percent urea 
rejection from a feed solution containing sodium chlo-
ride and urea (each at 10 g/l.)
Flowmeter 
Capacitive	
.
	 krgon Electrodes	 Matching	 Inlet Substrate	
J,::c:rk 
•	 R 	
I_-_ACPowerI Generator 
Monomer II	 To Vacuum 
Inlet	 Pumps 
The procedure for forming the membranes first re-
quires that degassed allyl amine be admitted via a 
needle valve to a bell jar which has been evacuated 
to a background pressure of less than 0.13 N/rn2 
(10-3
 torr); see diagram. System pressure (controlled 
by flow of allyl amine) is stabilized at about 13 N/rn2, 
and then a stream of argon or inert gas is allowed to 
enter the bell jar. When the total pressure (amine 
flow and argon flow) is at about 27 N/rn2, HF energy
is applied until a discharge is initiated. The system is 
operated until a desired thickness of film has been de-
posited on the substrate (usually a membrane 0.1- or 
0.025-sm thick with its shiny side up). The distance 
from the substrate to the lower (ground) electrode is 
about 4 cm. 
The plasma polymerization of allyl amine proceeds 
smoothly, and a light tan polymer deposit forms 
readily. Film thicknesses ranging from 0.8 to 1.6 m 
can be obtained within S to 40 minutes. Films pro-
duced in 88 minutes at 40 watts of net RFpower dem-
onstrated the rejection values given above; films pro-
duced after 1% hours of polymerization were found 
to be impermeable. Water fluxes of 185 l/m2/day 
were achieved (3.3 gal/ft2/day). 
Advantages of the plasma polymerization technique 
for producing reverse-osmosis membranes include: 
control of film thickness by control of plasma para-
meters, a wide variety of substrates and substrate 
configurations can be coated, deposition times are 
short, and there is high adhesion of films to the sub-
strate. Membranes produced by plasma polymeriza-
tion have few imperfections (i.e., pinhole-free) and 
they need be only 1.0-sm thick or less for high salt re-
jection; moreover, the films are dry (no storage prob-
lems) and a minimal amount of compaction is antic-
ipated during reverse osmosis. 
Plasma polymerization appears to provide a new 
approach to the synthesis of reverse-osmosis mem-
branes, and it is conceivable that a large variety of 
organic monomers can be polymerized by the de-
scribed technique.
(continued overleaf) 
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.
https://ntrs.nasa.gov/search.jsp?R=19720000709 2020-03-17T03:43:12+00:00Z
Note: 
Requests for further information may be directed 
to:
Technology Utilization Officer 
Ames Research Center 
Moffett Field, California 94035 
Reference: TSP 72-10710 
Patent status: 
Inquiries concerning rights for the commercial use
of this invention should be addressed to: 
NASA Patent Counsel 
Mail Code 200-1A 
Ames Research Center 
Moffett Field, California 94035 
Source: John R. Hollahan and Theodore Wydeven 
Ames Research Center.. 
(ARC-10696) 
B72-10710
	 Category 04


Reverse-osmosis membranes by plasma polymerization

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