NASA/TM—2016-218944

February 2016

An Erratum was added to this report April 2016.

Bruce A. Banks

Science Application International Corporation, Cleveland, Ohio

Ryan J. Loftus

Alphaport, Inc., Cleveland, Ohio

Sharon K. Miller

Glenn Research Center, Cleveland, Ohio

Atomic Oxygen Erosion Yield Dependence Upon 

Texture Development in Polymers
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NASA/TM—2016-218944

February 2016

An Erratum was added to this report April 2016.

Bruce A. Banks

Science Application International Corporation, Cleveland, Ohio

Ryan J. Loftus

Alphaport, Inc., Cleveland, Ohio

Sharon K. Miller

Glenn Research Center, Cleveland, Ohio

Atomic Oxygen Erosion Yield Dependence Upon 

Texture Development in Polymers

National Aeronautics and

Space Administration

Glenn Research Center

Cleveland, Ohio 44135
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NASA/TM—2016-218944 iii 

Erratum 

Issued April 2016 for 

NASA/TM—2016-218944 

Atomic Oxygen Erosion Yield Dependence Upon Texture Development in Polymers 

Bruce A. Banks, Ryan J. Loftus, and Sharon K. Miller

February 2016 

Figures 5 and 8 have been corrected. 

Figure 5.—Erosion yield as a function of fluence for the eight materials tested in the 

hyperthermal exposure environment. 

Figure 8.—Erosion yield as a function of fluence for the eight materials tested in the thermal 

energy environment of a Faraday cage. 

NASA/TM—2016-218944 1 

Atomic Oxygen Erosion Yield Dependence Upon 

Texture Development in Polymers 

Bruce A. Banks 

Science Application International Corporation 

Cleveland, Ohio 44135 

Ryan J. Loftus 

Alphaport, Inc. 

Cleveland, Ohio 44135 

Sharon K. Miller 

National Aeronautics and Space Administration 

Glenn Research Center 

Cleveland, Ohio 44135 

Abstract 

The atomic oxygen erosion yield (volume of a polymer that is lost due to oxidation per incident atom) 

of polymers is typically assumed to be reasonably constant with increasing fluence. However polymers 

containing ash or inorganic pigments, tend to have erosion yields that decrease with fluence due to an 

increasing presence of protective particles on the polymer surface. This paper investigates two additional 

possible causes for erosion yields of polymers that are dependent upon atomic oxygen. These are the 

development of surface texture which can cause the erosion yield to change with fluence due to changes 

in the aspect ratio of the surface texture that develops and polymer specific atomic oxygen interaction 

parameters. The surface texture development under directed hyperthermal attack produces higher aspect 

ratio surface texture than isotropic thermal energy atomic oxygen attack. The fluence dependence of 

erosion yields is documented for low Kapton H (DuPont, Wilmington, DE) effective fluences for a 

variety of polymers under directed hyperthermal and isotropic thermal energy attack.

Introduction 

The reaction of directed low Earth orbital (LEO) atomic oxygen with hydrocarbon and halocarbon 

polymers causes oxidative erosion which results in the development of left-standing cone structures 

(Refs. 1 to 4). One of the most important characteristics of a polymer relating to its LEO durability is its 

atomic oxygen erosion yield which is the volume lost per incident atomic oxygen atom. The measurement 

of this value is most reliably performed by space experiments. Measurement of the atomic oxygen fluence 

in atoms/cm2

 is typically performed by measurement of the mass loss of polyimide Kapton H witness 

samples. A significant amount of LEO erosion data for Kapton H has been accumulated over several 

decades indicates its atomic oxygen erosion yield is 3.010–24 cm3

/atom (Ref. 5). Thus the measurement 

of Kapton H erosion has been adopted as the means of measuring the atomic oxygen fluence in LEO or 

the effective fluence in ground laboratory testing (Refs. 6 and 7). The Kapton H effective fluence is the 

fluence in LEO that would cause the same thickness of erosion of polyimide Kapton H as observed in 

ground laboratory testing. 

It is well known that atomic oxygen that does not react with polymers upon first impingement has a 

chance of scattering and reacting with other polymer surfaces if the surface is rough. Surface roughness 

has been found to increase as the square root of the fluence (Ref. 8). Thus, the atomic oxygen erosion 

yield may increase if a greater fraction of ejected oxygen atoms impinge upon adjoining polymer cones. 
NASA/TM—2016-218944 2 

Figure 1.—Dependence of aspect ratio (cone height to cone 

separation) change with atomic oxygen fluence upon atomic 

oxygen erosion yield. 

A growth in erosion yield should occur if the ratio of the height of the cones to the separation of the cones 

increases with fluence. If, as the cone height grows, the aspect ratio stays constant, then the erosion yield 

would not be expected to change with fluence. Similarly, if the aspect ratio decreases with fluence the 

erosion yield would be expected to decrease with fluence even though the roughness may increase. Such a 

decrease in erosion yield with fluence has been observed for FEP Teflon (DuPont, Wilmington, DE) 

(Ref. 9). This would imply that as the cones grow in height the spacing increases at a relatively higher 

rate causing a diminishing fraction of unreacted scattered atoms to impinge upon polymer surfaces. 

Figure 1 compares the effects of changing aspect ratios with fluence on erosion yield for various 

scenarios. 

Knowledge of the erosion yield dependence on atomic oxygen fluence is important for Kapton H 

because Kapton H is the accepted measuring stick for fluence and if its erosion yield varies with fluence 

then accurate fluence measurement becomes more complex. Past and planned atomic oxygen fluence 

monitors utilize Kapton H fluence witness samples for calibration which rely on knowledge of erosion 

yield dependence on fluence (Refs. 10 and 11). To address these issues, an experimental investigation of 

the possible changes of the atomic oxygen erosion yield with fluence for Kapton H and a few other 

polymers was conducted for both hyperthermal and thermal energy atomic oxygen and is reported herein. 

The intent of this paper is to compare the experimental change in the erosion yields of Kapton H and 

several other polymers with increasing fluence for relatively low fluences (<21021 atoms/cm2

) when the 

surface texture is developing. 

Apparatus and Procedure 

A low frequency hyperthermal RF plasma asher was used to measure ground laboratory atomic 

oxygen erosion yields using dehydrated mass loss of Kapton H witness samples. The hyperthermal asher 

was an LF-5 Axic plasma asher, operated on air, at a frequency of 35 kHz and found to produce an atomic 

oxygen impact energy of ~0.26 eV (Ref. 12). The low frequency LF-5 Axic plasma asher, with active 

electrodes above the grounded sample plane, produced an air plasma in which directed hyperthermal 

atomic oxygen beam impinges with normal incidence upon test samples. The result of this direct 

impingement causes left-standing cones to be etched on the sample surfaces that are typical of LEO 

hyperthermal atomic oxygen erosion. The energy of impacting atoms or ions is thought to be below 10’s 

of electron volts because it was below the sputter threshold of silicon dioxide as measured in high fluence 

testing of thin film SiO2 coated Kapton. The LF-5 Axic plasma asher was operated using two different 

sample exposure configurations. The first test consisted of ten 1.27 cm diameter samples placed on an 

aluminum plate and exposed to directed hyperthermal atomic oxygen attack as shown in Figure 2. 

 
NASA/TM—2016-218944 3 

Figure 2.—Samples on a flat plate for directed hyperthermal atomic oxygen 

exposure in a 35 kHz hyperthermal asher. 

Figure 3.—Samples in a Faraday cage with a loose fitting lid for thermal atomic 

oxygen exposure in a 35 kHz hyperthermal asher. 

The second configuration was with the same set of ten materials but placed within a Faraday cage which 

would cause thermal accommodation (~0.04 eV energy) of the atoms entering the cage as well as shield out 

most of the charged atoms, charged molecules, and ultraviolet radiation is shown in Figures 3 and 4. 
NASA/TM—2016-218944 4 

Figure 4.—Cross-section of the Faraday cage. 

TABLE 1.—LIST OF MATERIALS TESTED FOR 

EROSION YIELD DEPENDENCE ON 

ATOMIC OXYGEN FLUENCE 

Sample materials Symbol 

Kapton H PI(H) 

FEP Teflon FEP 

Epoxy EP 

Polypropylene PP 

Chlorotrifluoroethylene CTFE 

Polycarbonate PC 

Kapton HN PI(HN) 

Polyetherimide PEI 

During most of the testing the hyperthermal exposure tray was placed on top of the Faraday cage for 

convenience of allowing both atomic oxygen exposures to occur simultaneously. Each type of exposure 

occurred in increments where new Kapton H samples were used to measure each incremental fluence and 

placed in with other polymers (that were not changed) to measure their erosion yield (using mass loss) for 

each increment. The samples were weighed after 48 hour periods of vacuum dehydration using a Sartorius 

microgram balance. A list of materials tested in both the hyperthermal exposures and Faraday cage 

exposures is shown in Table 1. 

Samples were simply laid on a flat aluminum surface rather than in sample holders for the 

hyperthermal exposures or in the Faraday cage. This minimized mass change inconsistencies if they were 

placed in sample holders due to varying areas of exposure to the directed atomic oxygen during the many 

weight measurements needed for each sample. Small increments of Kapton H effective fluence were used 

(typically 1.461020 atoms/cm2

) to try to observe the effects of the development of surface texture upon 

the erosion yields. 

Results and Discussion 

Direct Hyperthermal Atomic Oxygen Exposure Tests 

The 22.58 hour atomic oxygen exposure of the sample plate with 10 Kapton H samples was used to 

make a flux map for the exposure plate which resulted in an average Kapton H effective flux of 

4.861015 atoms/(cm2

 sec) and a fluence of 3.951020 atoms/cm2. This flux map was used for the first two 

fluence increments. The resulting ratio of flux at each intended sample location relative to the sample in 

position one is given in Table 2. 

For the remainder of the fluence increments, the witness plate was placed on top of the Faraday cage. 

A new flux map was made for this configuration and is shown in Table 3. 

Two Kapton H fluence witness samples were changed out with new Kapton H samples for each 

increment of exposure while the other samples received accumulated atomic oxygen exposure increments. 

Tables 2 and 3 were then used to compute the accumulated Kapton H effective fluence of all the materials 

listed in Table 1. 

Figure 5 shows the results of measuring the erosion yield as a function of fluence for the nine 

materials tested in the hyperthermal exposure environment. 
NASA/TM—2016-218944 5 

TABLE 2.—RATIO OF FLUX AT EACH SAMPLE LOCATION 

RELATIVE TO THE FLUX IN POSITION 1 FOR 

THE FIRST TWO FLUENCE INCREMENTS 

Sample position Flux relative to position 1 

1 1.00 

2 0.96 

3 0.96 

4 0.99 

5 1.06 

6 0.95 

7 0.89 

8 0.89 

9 0.92 

10 1.01 

TABLE 3.—RATIO OF FLUX AT EACH SAMPLE LOCATION 

RELATIVE TO THE FLUX IN POSITION 1 FOR 

THE LAST SEVEN FLUENCE INCREMENTS 

Sample position Flux relative to position 1 

1 1.00 

2 0.89 

3 0.85 

4 0.90 

5 1.04 

6 1.05 

7 1.02 

8 0.87 

9 0.84 

10 1.11 

Figure 5.—Erosion yield as a function of fluence for the eight materials tested in the 

hyperthermal exposure environment. 

 
NASA/TM—2016-218944 6 

As can be seen in Figure 5, the erosion yield for epoxy and polypropylene increase with fluence; 

polycarbonate, Kapton H (PI (H) DuPont, Wilmington, DE) and PI-HN, and polyetherimide (PEI) remain 

relatively constant with fluence; and chlorotrifluoroethylene (CTFE) and fluorinated ethylene propylene 

(FEP) have erosion yields that decrease with fluence. The fact the erosion yield for Kapton H and HN are 

relatively constant with fluence is helpful because it is relied upon for measuring atomic oxygen fluence. 

The decrease in erosion yield of FEP observed in the hyperthermal asher is in difference to the observed 

increase in erosion yield from low Earth orbital data (Ref. 6). This difference in results is thought to be 

due to a stronger effect on erosion yield that is dependent on equivalent sun hours (ionizing radiation and 

temperature) than atomic oxygen fluence. It should be noted that the erosion yield decreases with fluence 

for high hyperthermal fluences where ash content begins to play a shielding role as described (Ref. 13). 

To compare the surface morphology of materials that had demonstrated erosion yields which increase or 

decrease with fluence, scanning electron microscopy was performed on FEP and epoxy samples which were 

exposed to two different fluences. Figures 6 and 7 show scanning electron microscope images of FEP and 

epoxy surfaces respectively that have been exposed to two different hyperthermal atomic oxygen fluences. 

As can be seen from Figures 6 and 7, although the images appear different at different fluences, it is 

difficult to clearly attribute the differences in erosion yields for the fluences indicated to changes in aspect 

ratio of the surface features. It is thought that the material differences in the development of surface 

texture, trapping of scattered oxygen atoms, and angular dependent reaction characteristics may play a 

significant role in erosion yield dependence changes with fluence. 

Figure 6.—FEP Teflon that has been exposed to two different hyperthermal atomic oxygen Kapton H effective fluences: 

(a) 5.871020 atoms/cm2, (b) 1.941021 atoms/cm2. 

Figure 7.—Epoxy that has been exposed to two different hyperthermal atomic oxygen Kapton H effective fluences: 

(a) 5.191020 atoms/cm2, (b) 1.221021 atoms/cm2. 
NASA/TM—2016-218944 7 

Figure 8.—Erosion yield as a function of fluence for the eight materials tested in the thermal energy 

environment of a Faraday cage. 

Thermal Energy Faraday Cage Exposure Tests 

A 17.23 hour atomic oxygen exposure of the sample plate with 10 Kapton H samples was used to 

make a flux map for 10 Faraday cage sample locations which resulted in an average Kapton H effective 

flux of 6.11015 atoms/(cm2

 sec) and a fluence of 3.731020 atoms/cm2. The resulting ratio of flux at each 

intended sample location relative to the flux in a specific position was measured. Two sample positions 

were used for Kapton H fluence witness which were changed out with new Kapton H samples for each 

increment of exposure while the other samples were left in place to receive cumulative atomic oxygen 

exposure for each increment. 

Figure 8 shows the results of measuring the erosion yield as a function of fluence for the eight 

materials tested in the thermal energy environment within a Faraday cage. 

In contrast to the hyperthermal results in Figure 4, the erosion yield for epoxy decreases with fluence 

and for chlorotrifluoroethylene increases slightly with fluence. It is fortunate that Kapton H and HN 

(which are the most frequent materials used for fluence measurement) have erosion yields that are 

reasonably constant with fluence because their fluence measurements should not have to be adjusted as a 

function of fluence. 

Summary 

The atomic oxygen erosion yield of some polymers was experimentally found to change with atomic 

oxygen fluence. Eight polymers were tested experimentally under hyperthermal and isotropic thermal 

energy atomic oxygen attack and were found to produce results that varied from increasing, decreasing, 

and staying rather constant with fluence. It is believed that the material differences in the development of 

surface texture, trapping of scattered oxygen atoms, and angular dependent reaction characteristics may 

play a significant role in erosion yield dependence changes with fluence. Fortunately the materials most 

used for atomic oxygen fluence measurement, polyimide Kapton H and HN, were found to have an 

erosion yield that was rather independent of fluence both when exposed to hyperthermal and isotropic 

thermal energy atomic oxygen. 
NASA/TM—2016-218944 8 

References 

1. Banks, Bruce A., de Groh, Kim K., and Miller, Sharon K., “Low Earth Orbital Atomic Oxygen 

Interactions with Spacecraft Materials,” NASA/TM—2004-213400 and paper presented at the Fall 

2004 Meeting of the Materials Research Society, Boston Massachusetts, November 29-December 3, 

2004. 

2. Banks, B.A., Rutledge, S.K., Hunt, J.D., Drobotij, E., Cales, M.R. and Cantrell, G., “Atomic Oxygen 

Textured Polymers,” Presented at the Materials Research Society 1995 Spring Meeting, NASA TM 

106769, San Francisco, CA, April 17–21, 1995. 

3. Waters, D.L., Banks, B.A., de Groh, K.K., Miller, S.K., and Thorson, S.D., “Investigation into the 

Differences Between Atomic Oxygen Erosion Depth and Cone Height of Various Materials at 

Hyperthermal Energy,” High Performance Polymers Journal, Vol. 20, No. 4/5 August/October 2008 

and NASA/TM—2007-214374, March 2007, paper presented at the 10th International Symposium on 

Materials in a Space Environment & 8th International Conference on Protection of Materials and 

Structures in a Space Environment, Collioure, France, June 19–23, 2006. 

4. Banks, B.A., Miller, S.K., and de Groh, K., “Low Earth Orbital Atomic Oxygen Interactions with 

Materials,” paper presented at the Second International Energy Conversion Engineering Conference 

sponsored by the American Institute of Aeronautics and Astronautics, AIAA-2004-5638, 

NASA/TM—2004-213223, Providence, Rhode Island, August 16–19, 2004. 

5. de Groh, K.K. and Banks, B.A., “MISSE 2 Peace Polymers Erosion Morphology Studies,” Paper 

presented at the 11th International Symposium on Materials in a Space Environment, Aix en 

Provence, France, September 15–18, 2009. 

6. deGroh, K.K., Banks, B.A., McCarthy, C.E., “Spacecraft Polymers Atomic Oxygen Durability 

Handbook DBK-6024,” Approved and published by the NASA Office of the Chief Engineer, 

June 27, 2014.

7. ASTM E 2089-00, “Standard Practices for Ground Laboratory Atomic Oxygen Interaction Evaluation 

of Materials for Space Applications,” June 2000. 

8. Banks, Bruce A. and Rutledge, Sharon K., de Groh, K., Chan, A., Sahota, M., “The Development of 

Surface Roughness and Implications for Cellular Attachment in Biomedical Applications,” 

NASA/TM—2001-211288, presented at the 2001 Fall Meeting of the Materials Research Society, 

Boston MA, November 26–30, 2001. 

9. Miller, S.K., Banks, B.A., and Waters, D.L., “Investigation into the Differences in Atomic Oxygen 

Erosion Yields of Materials in Ground Based Facilities Compared to Those in LEO,” High 

Performance Polymers Journal, Vol. 20, No. 4/5 August/October 2008 and paper presented at the 

10th International Symposium on Materials in a Space Environment & 8th International Conference on 

Protection of Materials and Structures in a Space Environment, Collioure, France, June 19–23, 2006. 

10. Banks, B., Miller, S., and Waters, D., “Materials International Space Station Experiment -6 

(MISSE-6) Atomic Oxygen Fluence Monitor Experiment,” NASA/TM—2010-216755, Paper 

presented at the 2010 National Space and Missile Materials Symposium (NSMMS) Scottsdale, 

Arizona, June 38-July 1, 2010. 

11. Banks, B.A., Miller, S.K., Sechkar, E.A., and Loftus, R.J. “Atomic Oxygen Fluence Monitors for 

Materials International Space Station Experiments 7 and –X,” NASA/TM—2014-218379, Sept. 2014. 

12. Banks, B.A., Keubel, C.A., “Atomic Oxygen Energy in Low Frequency Hyperthermal Ashers,” 

NASA/TM—2014-218412, Nov. 2014. 

13. Banks, B.A., Simmons, J.C., de Groh, K.K., Miller, S.K., “The Effect of Ash and Inorganic Pigment 

Fill on the Atomic Oxygen Erosion of Polymers and Paints,” Proceedings of the “12th International 

Symposium on Materials in the Space Environment (ISMSE 12),” Noordwijk, The Netherlands 

(ESA SP-705, February 2013).