A polymeric substrate is coated with a metal oxide film to provide oxidation protection in low Earth orbital environments. The film contains about 4 volume percent polymer to provide flexibility. A coil of polymer materials moves through an ion beam as it is fed between reels. The ion beam first cleans the polymer material surface and then sputters the film material from a target onto this surface

Banks, A.

Mirtich, M. J.

Sovey, J. S.

English

NASA Technical Reports Server

United States Patent [191 [ i l l  Patent Number: 4,604,18 1 
Mirtich et al. [45] Date of Patent: Aug. 5, 1986 
[54] APPARATUS FOR PRODUCING 4,013,532 3/1977 Corima et al. ........................ 427/41 
OXIDATION PROTECTION COATINGS FOR 4,046,712 9/1977 Cairns et al. ........................ 252/447 
4,091,138 5/1978 Takagi et al. ....................... 428/209 
4.096.315 6/1978 Kubacki 427/41 
POLYMER§ ................................ 
[75] Inventors: 
[73] Assignee: 
[21] Appl. No.: 
[22] Filed: 
Michael J. Mirtich, North Olmsted; 
James S .  Sovey, Strongsville; Bruce 
A. Banks, Olmsted Township, 
Cuyahoga County, all of Ohio 
The United States of America as 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
961,235 
Jul. 31, 1985 
Related US. Application Data 
[62] Division of Ser. No. 649,330, Sep. 14, 1984, Pat. No. 
4,560,577. 
[51] Int. Cl.4 .............................................. C23C 14/46 
[52] US. C1. ................................ 204/298; 204/192 C, 
204/192 D 
Field of Search ............... 204/298, 192 R, 192 D, 
204/192 C 
[58] 
[561 References Cited 
U.S. PATENT DOCUMENTS 
3,514,388 SA970 Brumfield et al. .................. 204/192 
3,895,155 7/1975 Shukuri et al. ..................... 428/702 
3,984,581 10/1976 Dobler et al. ......................... 427/35 
. .  
4,112,137 9/1978 Zega ...................................... 427/38 
4,199,650 4/1980 Mirtich et al. ...................... 428/421 
4,278,493 7/1981 Petvai .................................. 156/643 
4,344,996 8/1982 Banks et al. ......................... 428/141 
4,354,911 10/1982 Dodd et al. .................. 204/192 EC 
4,404,263 9/1983 Hodes .................................. 428/564 
OTHER PUBLICATIONS 
J. L. Vossen et al., Thin Film Processes, Academic Press, 
New York, 1978, pp. 189-198, 515. 
Primary Examiner-John F. Niebling 
Assistant Examiner-William T. Leader 
Attorney, Agent, or Firm-Gene E. Shook; John R. 
Manning 
[571 ABSTRACT 
A polymeric substrate 10 is coated with a metal oxide 
film 22 to provide oxidation protection in low earth 
orbital environments. The film contains about 4 volume 
percent polymer to provide flexibility. 
A coil of polymer material 30,42 moves through an ion 
beam 14 as it is fed between reels. The ion beam first 
cleans the polymer material surface and then sputters 
the film material from a target 24 onto this surface. 
8 Claims, 4 Drawing Figures 
https://ntrs.nasa.gov/search.jsp?R=19860023097 2020-03-23T07:19:05+00:00Z
U.S. Patent Aug. 5,1986 Sheet 1 of2 4,604,181 
18 
FIG. I 
I 
. 
FIG. 2 
U.S. Patent Aug. 5,1986 Sheet 2 of 2 4,604,18 1 
FIG. 3 
FIG. 4 
4,604,18 1 
1 
APPARATUS FOR PRODUCING OXIDATION 
PROTECTION COATINGS FOR POLYMERS 
ORIGIN OF THE INVENTION 
ees of the U.S. Government and may be manufactured 
and used by or for the Government for governmental 
purposes without the payment of any royalties thereon 
or therefor. 10 apparatus. 
imide or other thermoplastic resin, to form an electri- 
cally conducting insulated coating. 
Zega U.S. Pat. No. 4,112,137 is directed to a coating 
method wherein a metal source is bombarded by an 
5 electron beam. This metal is used to coat glass surfaces. 
with a metal Plating method for coating a large ntmber 
of metal and nonmetal parts at the same time using a 
metal. Argon gasses are employed in the ion plating 
The invention described herein was made by employ- Brumfield et a1 U.S. Pat. NO. 3,514,388 iS concerned 
_ _  
None of the prior art patents discloses a coating for 
oxidation protection. Moreover, none of these patents 
employs an ion beam for cleaning the substrate prior to 
coating. 
STATEMENT OF CoPENDENCY This 
is a division of application Ser. No. 649,330 which was 
filed Sept. 14, 1984 and issued as U.S. Pat. No. 
4,560,577. 15 ~. 
DESCRIPTION DISCLOSURE OF THE INVENTION 
1. Technical Field A polymer material is exposed to an ion beam to clean 
This invention relates to the protection of polymeric absorbed gasses and contaminants from its surface. The 
materials, such as polyimides. The invention is particu- ion cleaned polymer surface is then immediately ion 
larly concerned with providing an oxidation protection 2o beam sputter coated with a protective thin film. Materi- 
barrier to these materials when they are exposed to low als may be co-sputtered to form a coating containing 
earth orbital environments. both metal oxides and polymers. 
Various polymers exhibit weight loss when exposed The substrate shape, ion specie, ion energy and ion 
to a near earth orbital environment. The mechanism beam current density utilized can be varied. No substan- 
appears to be oxidation by the energetic incidence of 25 tial change in the polymer or materials characteristics is 
atomic oxygen atoms associated with high relative ve- involved. By putting a lightweight thin flexible film on 
locity of near earth spacecraft and the high abundance the polymer, all of the demonstrated advantages of the 
of atomic oxygen in low earth orbit. It has been demon- substrate material can be utilized with the added oxida- 
strated that organic polymers, such as polyimides, have 3o tion protection of the oxide polymer coating. 
high rates of weight loss in this environment. 
Because many of these polymers are used as struc- BRIEF DESCRIPTION OF THE DRAWINGS 
tural or thermal blankets, a Problem develops because The advantages and novel features of the invention 
these materials become so thin through oxidation that will be fully apparent from the following detailed 
they lose their structural or thermal integrity. In partic- description when read in connection with the accompa- 
ular, a polyimide is typically used as a solar array blan- 35 nying drawings wherein like numerals are used 
ket material. If this material is exposed long enough, throughout to identify like parts. 
mechanical and electrical failures are encountered in FIG. is a schematic view showing a polymer sheet 
being ion beam cleaned in accordance with the present the spacecraft power system. Alternatives to polymers which oxidize have been invention; considered by filling these materials with additives that 40 FIG. is a schematic view showing the ion cleaned reduce their oxidation rates. Other solutions have been polymer surface of FIG. being immediately ion beam proposed, such as using alternate materials, including sputter-coated with a protective thin film; 
FIG. 3 is a schematic view showing a single ion silicon rubber or polytetrafluoroethylene, which exhibit lower oxidation rates. All of these solutions to the orbi- source for both ion cleaning and codeposition; and tal oxidation problem represent major changes in de- 45 
ymer characteristics, such as strength, weight, optical bodiment of the invention utilizing multiple ion sources 
absorptance, emittance, tearing, creep, and adhesion for ion ‘leaning and codepositon. 
properties. BEST MODE FOR CARRYING OUT THE 
INVENTION 
provide oxidation protection for polymeric materials, 
such as polyimides, in a low earth orbital environment. there is shown in 
FIG. 1 a film or sheet 10 of a polymeric material such as 2. Prior Art 
Mirtich and Sovey U.S. Pat. No. 4,199,650 discloses a Polyimide known commercially as KaPton having a 
the treating ofpolyimide and fluorinated ethylene prop- 55 surface 12 that is to be covered with an oxidation barrier 
ylene polymers using an electron bombardment argon for exposure to a low earth orbital env~r~nment. The 
source. This treatment modifies the electrical and opti- surface 12 ofthe sheet 10 is exposed to abeam 14 of500 
cal properties of the polymers. eV to 2000 eV argon ions at current densities of 0.1 
Dobler et a1 U.S. Pat. No. 3,984,581 discloses a mA/cm2 to 10 mA/cm2. 
method wherein multilayer coatings of silicon oxide and 60 The argon ion beam 14 is furnished by an electron 
another metal oxide are provided on the surface of an bombardment ion Source 16 of the type developed for 
organic polymeric plastic material for antireflective electric propulsion technology. Argon gas from a suit- 
purposes. The oxides are vaporized by an electron able source, not shown, is fed through a line 18 to a 
beam, and the ionized molecules are deposited on the cathode in a chamber within the source 16 where the 
substrate. 65 gas is ionized. The argon ions are retained within this 
Takagi U.S. Pat. No. 4,091,138 discloses a coating chamber which also contains an anode about its outer 
method wherein a metal is ionized in the crucible. This periphery. Such an ion source is described in “Ad- 
metal is deposited on a film material, such as a poly- vances in Electronic and Electron Physics” by H. R. 
sign. These solutions also sacrifice other important pol- is a view showing an em- 
It is, therefore, an object of the present invention to 50 
Referring now to the 
. 
4,604,181 
2 J 
Kaufman, vol. 36, pages 265-373 (1974). It will be ap- 
preciated that other gases, in addition to argon can be 
used to form the bombarding ions in the beam 14. For 
example, xenon and hydrogen may be used, and even 
hydrocarbons may be provided in the ion source 16. 
Extraction of the beam 14 is accomplished by a two 
grid ion optic system 20. Such a system is described in 
AIAA Paper No. 76-1017 entitled “A 30 cm Diameter 
Argon Ion Source”. Such a double grid system includes 
both the screen grid and accelerator grid. The screen 
grid serves to contain the discharge plasma while form- 
ing the necessary ion optics to prevent direct impinge- 
ment of the accelerated ions into the accelerator grid. 
Ions in the near vicinity of the screen grid have a high 
probability of being accelerated through the openings in 
the screen and the accelerator grids because of the high 
electric fields present at the grids. 
Neutralization of the ions is achieved by the interjec- 
tion of electrons into the beam 14. A suitable neutralizer 
in the form of a downstream cathode provides these 
electrons. 
The electron bombardment ion source 16 is located in 
the vacuum facility which is sufficiently large to pre- 
vent back sputtered facility materials from contaminat- 
ing the process. The operating pressure within the vac- 
uum facility during sputtering is about 1 X torr or 
lower. 
Immediately after cleaning the polymer sheet PO is 
mounted in the vacuum chamber in the position shown 
in FIG. 2. The ion cleaned surface 12 is then ion sputter 
coated with a protective thin film 22 having a thickness 
between about 50 angstroms and about 800 angstroms. 
This is accomplished by mounting a sputter target 24 in 
the ion beam 14. 
5 
10 
15 
20 
25 
30 
The sputter target 24 is composed of two types of 35 
materials. A metal oxide, such as Si02 or A1203 forms a 
larger portion 26. A flexible polymer with a low oxida- 
tion rate, such as polytetrafluoroethylene or silicone 
rubber, forms a small portion 28. 
ther spatially separated or overlapping. The purpose of 
the metal oxide materials is to provide an already oxi- 
dized surface on the polymer to be protected. A protec- 
tive coating 22 consisting essentially of 100% metal 
oxide may not have suitable flexibility bo retain good 45 
integrity without cracking or spalling on substrates 10 
that are expected to be bent over a small radii of curva- 
ture. Thus, the purpose of the polymer portion 28 of the 
sputter target 24 is to provide a small amount, i.e. less 
than about 20 volume percent, of molecularly mixed 50 
polymer content to the protecting film 22 to give it 
additional flexible properties. 
The area of the polymer target portion 28 is typically 
much smaller than the metal oxide target portion. 26 
because only a small amount of the polymer produces a 55 
large gain in film flexibility. Also, it is desirable to have 
the oxidation protection dominated by the metal oxide 
of the larger portion 26. 
These target material portions 26 and 28 may be ei- 40 
ALTERNATE EMBODIMENTS OF THE 6o 
INVENTION 
Referring now to FIGS. 3 and 4, there is shown reel 
to reel production of a coated polymer material in 
coiled form. In the embodiment of FIG. 3 the same ion 
beam is used for both sputter cleaning and film deposi- 65 
tion in the manner shown in FIGS. 1 and 2. In the em- 
bodiment of FIG. 4 separate ion beams are used for 
cleaning and film deposition. 
4 
Referring now to FIG. 3 a coil of polymer material 30 
to be coated passes from a payout reel 32 over a roller 
34 to a takeup reel 36. The roller 34 is located in the ion 
beam 14. A target of the type shown in FIG. 2 is like- 
wise mounted in the ion beam 14. 
As the polymer material 30 moves from the payout 
reel 32 to the roller 34, a surface portion 38 is ion beam 
cleaned in the manner described above in connection 
with FIG. 1. After the ion beam cleaned surface portion 
passes over the roller 34, a predetermined surface por- 
tion 40 is coated in a manner described above in connec- 
tion with the embodiment shown in FIG. 2. 
In the embodiment of FIG. 4 a coil of polymer mate- 
rial 42 to be coated is fed from a payout reel 44 to a 
takeup reel 46 in a manner similar to that described 
above in connection with the embodiment shown in 
FIG. 3. A beam 48 of argon ions from a source 50 cleans 
a surface portion 52 of the polymer material 42 in the 
manner described above in connection with the embodi- 
ment of FIG. 1. 
A pair of ion sources 54 and 56 provide ion beams 58 
and 60, respectively, to bombard a target 62 in the man- 
ner discussed above in connection with FIG. 2. The 
target 62 is similar to the target 24 in that it includes a 
metal portion 64 and a polymer portion 66. A surface 
portion 68 of the polymer material 42 is coated in the 
manner described above in connection with FIG. 2 as 
the material moves between the reel 44 and the reel 46. 
In all the aforementioned embodiments the deposited 
films are typically 50 angstroms4300 angstroms thick. 
This thickness provides desirable flexibility and surface 
protection. 
By way of example, a polymer material was covered 
with a coating comprising 96 volume percent of Si02 
and 4 volume percent polytetrafluoroethylene in accor- 
dance with the present invention. This coating reduced 
oxidation rates of the polyimide material by a factor of 
at least five hundred in shuttle orbiter tests. 
While several embodiments of the invention have 
been described it will be appreciated that various modi- 
fications can be made without departing from the spirit 
of the invention or the scope of the subjoined claims. 
For example, the metal oxide portions 26 and 64 of the 
targets 24 and 6% may be any oxide whose mechanical, 
optical, electrical and adhesion properties are desirable. 
Conductive metal oxides, such as indium and/or tin 
oxide, may be used to provide a conductive as well as an 
oxidation protecting surface. It is further contemplated 
that the metal oxide and/or polymer sputter deposited 
coating 22 may be a mixture of one or more oxides 
and/or polymers. 
In certain applications the sputter cleaning and metal 
oxide deposition could be accomplished by R F  sputter 
cleaning and RF sputter deposition. Also, D.C. sputter 
deposition or electron beam evaporation may be used 
instead of the ion beam cleaning and ion beam deposi- 
tion of metal oxides. For some polymers, thermal evap- 
oration might be used instead of the ion beam sputter- 
ing. Such a thermal evaporation step could be used with 
polytetrafluoroethylene, for example. 
The arrangement of the ion sources as described in 
FIGS. 1 through 4 and the sputter targets may be spa- 
tially varied. Also, the ratio of polymer to metal oxides 
can be varied. This ratio may be varied from 100% 
metal oxide to 100% polymer. 
We claim: 
1. Apparatus for coating a polymeric material with an 
oxidation protecting film comprising 
4,604,18 1 
5 6 
polymeric material; and 
an ion beam source for furnishing an ion beam for 
cleaning a surface of said polymeric material, and 
a sputter target mounted such that a beam of ions 
from an ion source can bombard said target for ion 
sputter coating said ion beam cleaned surface with 5 rial from Oxikhm comprising 
a mixture of metal oxide and polymer to form said 
oxidation protecting film, said sputter target 
prising 
a first portion of a metal oxide material, and 
a second portion of a polymer 
an ion beam for ion beam cleaning said surface of said 
another ion beam for bombarding said sputter target. 
6. Coating apparatus for Protecting a Polymeric mate- 
a 
means for mounting said material in said chamber, 
means for producing a beam of ions in said vacuum 
chamber for cleaning absorbed gases and contami- 
a sputter target having a metal oxide portion and a 
polymer portion positioned within said chamber 2. Apparatus for coating a polymeric material as for simultaneous co-sputtering by ions from said claimed in claim 1 wherein the first portion of the sput- ion producing means thereby sputter coating said ter target is a metal oxide selected from the group con- 15 cleaned surface in said vacuum chamber immedi- 
ately after cleaning with a continuous thin film sisting of Si02 and Al2O3. 
comprising a metal oxide and a polymer in a prede- 3. Apparatus for coating a polymeric material as 
termined ratio to form an oxidation barrier. claimed in claim 1 wherein the second portion of said 
sputter target is a polymer material selected from the claimed in claim 6 wherein 
group consisting of PolYtetrafluorethYlene and silicone 20 the polymer portion of the target comprises a material 
rubber. selected from the group consisting of polytetrafluoro- 
4. Apparatus for coating a polymer material as ethylene and silicon rubber. 
claimed in claim 1 wherein a single ion beam cleans said 8. Apparatus for coating a polymeric material as 
surface of said polymeric material and bombards said claimed in claim 6 wherein the metal oxide portion of 
target. 25 said sputter target is a metal oxide selected from the 
5. Apparatus for coating a polymeric material as group consisting of Si02 and Al2O3. 
chamber9 
having a 10 nmts from a surface of said material, and 
low oxidation rate. 
7. Coating apparatus 
claimed in claim 1 including * * * * *  
30 
35 
40 
45 
50 
55 
60 
65 


Apparatus for producing oxidation protection coatings for polymers

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