Kim K. de GrohGlenn Research Center, Cleveland, Ohio

Catherine E. McCarthy and Kshama M. GirishHathaway Brown School, Shaker Heights, Ohio

Bruce A. BanksScience Applications International Corporation, Cleveland, Ohio

Carolyn Kaminski, Erica E. Youngstrom, Maura Lillis, Christiane A. Youngstrom, Anne M. Hammerstrom, Stephanie Hope, and Laura M. MarxHathaway Brown School, Shaker Heights, Ohio

Rehydration Data for the Materials International Space Station Experiment (MISSE) Polymer Films

NASA/TM—2019-220063

February 2019

https://ntrs.nasa.gov/search.jsp?R=20190001084 2020-06-15T06:54:17+00:00Z

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Kim K. de GrohGlenn Research Center, Cleveland, Ohio

Catherine E. McCarthy and Kshama M. GirishHathaway Brown School, Shaker Heights, Ohio

Bruce A. BanksScience Applications International Corporation, Cleveland, Ohio

Carolyn Kaminski, Erica E. Youngstrom, Maura Lillis, Christiane A. Youngstrom, Anne M. Hammerstrom, Stephanie Hope, and Laura M. MarxHathaway Brown School, Shaker Heights, Ohio

Rehydration Data for the Materials International Space Station Experiment (MISSE) Polymer Films

NASA/TM—2019-220063

February 2019

National Aeronautics andSpace Administration

Glenn Research CenterCleveland, Ohio 44135

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NASA/TM—2019-220063 1

Rehydration Data for the Materials International Space Station Experiment (MISSE) Polymer Films

Kim K. de Groh

National Aeronautics and Space Administration Glenn Research Center Cleveland, Ohio 44135

Catherine E. McCarthy and Kshama M. Girish

Hathaway Brown School Shaker Heights, Ohio 44122

Bruce A. Banks

Science Applications International Corporation Cleveland, Ohio 44135

Carolyn Kaminski, Erica E. Youngstrom, Maura Lillis, Christiane A. Youngstrom,

Anne M. Hammerstrom, Stephanie Hope, and Laura M. Marx Hathaway Brown School

Shaker Heights, Ohio 44122

Abstract Atomic oxygen erosion of polymers in low Earth orbit (LEO) poses a serious threat to

spacecraft performance and durability. Forty thin film polymer and pyrolytic graphite samples, collectively called the PEACE (Polymer Erosion and Contamination Experiment) Polymers, were exposed to the LEO space environment on the exterior of the ISS for nearly four years as part of the Materials International Space Station Experiment 1 & 2 (MISSE 1 & 2) mission. The purpose of the MISSE 2 PEACE Polymers experiment was to determine the atomic oxygen (AO) erosion yield (Ey, volume loss per incident oxygen atom) of a wide variety of polymers exposed to the LEO space environment. The Ey values were determined based on mass loss measurements. Because many polymeric materials are hygroscopic, the pre-flight and post-flight mass measurements were obtained using dehydrated samples. To maximize the accuracy of the mass measurements, obtaining dehydration data for each of the polymers was desired to ensure that the samples were fully dehydrated before weighing. A comparison of dehydration and rehydration data showed that rehydration data mirrors dehydration data, and is easier and more reliable to obtain. Tests were also conducted to see if multiple samples could be dehydrated and weighed sequentially. Rehydration curves of 43 polymers and pyrolytic graphite were obtained. This information was used to determine the best pre-flight, and post-flight, mass measurement procedures for the MISSE 2 PEACE Polymers experiment, and for subsequent NASA Glenn Research Center MISSE polymer flight experiments.

NASA/TM—2019-220063 2

Introduction Spacecraft orbiting the Earth in the low Earth orbit (LEO) environment (between about 180

and 650 km) endure harsh environmental exposure conditions, including ultraviolet, x-ray and charged particle radiation, micrometeoroids and orbital debris and exposure to atomic oxygen (AO). Atomic oxygen erosion of polymers in LEO poses a serious threat to spacecraft performance and durability. Therefore in order to design high-performance durable spacecraft systems, it is essential to understand the AO erosion yield (Ey, the volume loss per incident oxygen atom, in cm3/atom) of polymers being considered for spacecraft applications.

Forty-one different thin film polymer samples, collectively called the PEACE (Polymer Erosion and Contamination Experiment) Polymers, were exposed to the LEO space environment on the exterior of the International Space Station (ISS) for four years as part of the Materials International Space Station Experiment 1 & 2 (MISSE 1 & 2) mission (Refs. 1 and 2). The MISSE 2 PEACE Polymers experiment was flown in sample tray E5 on the Passive Experiment Carrier 2 (PEC 2) Tray 1, which was flown in a ram facing flight orientation. Figure 1 is a photograph of MISSE PEC 2 being attached to the ISS Quest Airlock during an extravehicular activity (EVA). The MISSE 2 PEACE Polymers tray is visible in this photograph. Figure 2 is a photograph of the Quest Airlock showing the location of MISSE PEC 2. The purpose of the experiment was to determine the AO Ey of a wide variety of polymers exposed to the LEO space environment (Refs. 1 and 2). Figure 3 provides pre-flight and post-flight photos of the PEACE Polymers experiment in the E5 flight tray. Extensive AO erosion and color changes can be seen in the majority of polymers after four years of space exposure.

Figure 1. During a spacewalk on August 16, 2001, astronaut Patrick Forrester installs MISSE

PEC 2 on the ISS Quest Airlock.

MISSE PEACE Polymers Tray

NASA/TM—2019-220063 3

Figure 2. Photograph of the Quest Airlock and MISSE PEC 2 taken during the STS-105.

a.

b.

Figure 3. MISSE 2 PEACE Polymers experiment tray: a). Pre-flight, and b). Post-flight.

MISSE PEC 2

NASA/TM—2019-220063 4

The MISSE 2 PEACE Polymers experiment Ey values were determined based on mass loss measurements. Because many polymeric materials are hygroscopic and can undergo dramatic increase in mass with moisture (depending on thickness, temperature and humidity), the pre-flight and post-flight mass measurements were obtained using dehydrated samples. To ensure the polymers were in a fully dehydrated state before weighing, studies were conducted to characterize the hygroscopic nature of each polymer.

Ideally, it was believed that dehydration curves would be best to obtain because the goal was to verify samples were fully dehydrated prior to obtaining their mass. But, to obtain a dehydration curve a sample needs to be moved in and out of the vacuum chamber for each time-based mass data point. This makes it difficult, and time consuming, to accurately measure the time needed to fully dehydrate a polymer. Because rehydration should approximately mirror the dehydration process, a dehydration versus rehydration test was conducted. Based on results of the dehydration vs. rehydration test, rehydration curves were obtained for each of the PEACE polymers. The purpose of the rehydration curves was to characterize the hygroscopic nature of each polymer – specifically, to determine the amount of moisture each of the samples would take on, and how quickly. This information was used to determine the best pre-flight and post-flight mass procedures for the MISSE 2 PEACE Polymers experiment and following MISSE flight experiments.

Material and Procedures PEACE Polymers

The polymers characterized for rehydration included 41 polymers flown in the MISSE 2 PEACE Polymers experiment (Refs. 1 and 2), along with three additional polymers (cellulose nitrate (CN), polyvinylidene chloride (PVDC) and ultra-high molecular weight polyethylene (UHMWPE)). The MISSE flight ID, polymer material, trade name, abbreviation and film thickness for the polymers are provided in Table 1. The samples, for both the hydration tests and the flight samples, were cut into 1-inch circles from sheets of film using a double bow punch cutter and an Arbor press.

Sample Dehydration and Mass Samples were dehydrated in a vacuum desiccator at room temperature and maintained at a

pressure of 8.0 - 13.3 Pa (60-100 mTorr) with a mechanical roughing pump. Because the actual minimum time needed for dehydration of each polymer was unknown, samples were placed in the vacuum desiccators for a minimum of four days (96 hours), which was believed to be sufficient to allow complete dehydration of the samples. All testing was conducted at room temperature. Mass measurements for the majority of samples were taken using a Mettler M3 balance (± 10 µg). For the heavier samples, such as pyrolytic graphite, a Sartorius balance (± 50 µg) was used.

NASA/TM—2019-220063 5

Table 1. Materials Characterized for Rehydration Mass. MISSE 2 Serial # Material Abbreviation Trade Name(s) Thickness

(mils) 2-E5-6 Acrylonitrile butadiene styrene ABS Cycolac, Absylux 5 2-E5-7 Cellulose acetate CA Clarifoil, Tenite Acetate, Dexel 2 2-E5-8 Poly-(p-phenylene terephthalamide) PPDT Kevlar 29 fabric 2.2 2-E5-9 Polyethylene PE Polyethylene 2

2-E5-10 Polyvinyl fluoride PVF Tedlar TTR10SG3 (clear) 1

2-E5-11 Crystalline polyvinylfluoride w/white pigment PVF-W White Tedlar TWH10BS3 1

2-E5-12 Polyoxymethylene; acetal; polyformaldehyde POM Delrin, Acetal (natural) 10

2-E5-13 Polyacrylonitrile PAN Barex 210 2 2-E5-14 Allyl diglycol carbonate ADC CR-39, Homalite H-911 31 2-E5-15 Polystyrene PS Trycite 1000 2

2-E5-16 Polymethyl methacrylate PMMA Plexiglas, Acrylite (Impact Mod.) 2

2-E5-17 Polyethylene oxide PEO Alkox E-30 (powder) 29

2-E5-18 Poly(p-phenylene-2 6-benzo-bisoxazole), Balanced biaxial film PBO Zylon 1

2-E5-19 Epoxide or epoxy EP Hysol EA 956 88-92 2-E5-20 Polypropylene PP Contour 28 20 2-E5-21 Polybutylene terephthalate PBT Valox 357 3 2-E5-22 Polysulfone PSU Thermalux P1700, Udel P-1700 2 2-E5-23 Polyurethane PU, PUR Dureflex PS8010 2 2-E5-24 Polyphenylene isophthalate PPPA Nomex Crepe Paper T-410 2 2-E5-25 Pyrolytic graphite PG Pyrolytic Graphite 80 2-E5-26 Polyetherimide PEI Ultem 1000 10 2-E5-27 Polyamide 6 PA 6 Nylon 6 2 2-E5-28 Polyamide 66 PA 66 Nylon 66 2 2-E5-29 Polyimide (Clear) PI CP1 3

2-E5-30 & 2-E5-33 Polyimide (PMDA) PI Kapton H 5

2-E5-31 Polyimide (PMDA) PI Kapton HN 5 2-E5-32 Polyimide (BPDA) PI Upilex-S 1 2-E5-34 High temperature polyimide resin PMR-15 PMR-15 12-14 2-E5-35 Polybenzimidazole PBI Celazole 2 2-E5-36 Polycarbonate PC PEEREX 61 10 2-E5-37 Polyetheretherketone PEEK Victrex PEEK 450 3 2-E5-38 Polyethylene terephthalate PET Mylar A-200 2 2-E5-39 Chlorotrifluoroethylene CTFE Kel-f, Neoflon M-300 5 2-E5-40 Ethylene-chlorotrifluoroethylene ECTFE Halar 300 3 2-E5-41 Tetrafluorethylene-ethylene copolymer ETFE Tefzel ZM 3 2-E5-42 Fluorinated ethylene propylene FEP Teflon FEP 200A 2 2-E5-43 Polytetrafluoroethylene PTFE Chemfilm DF 100 2 2-E5-44 Perfluoroalkoxy PFA Teflon PFA 200 CLP 2 2-E5-45 Amorphous fluoropolymer AF Teflon AF 1601 2 2-E5-46 Polyvinylidene fluoride PVDF Kynar 740 3

N/A Cellulose nitrate CN Cellulose Nitrate 5 N/A Polyvinylidene chloride PVDC Saran 2

N/A Ultra-high molecular weight polyethylene UHMWPE Polyethylene 10

NASA/TM—2019-220063 6

Open-Close Trials Because of time constraints, it was not practical to dehydrate one sample in the desiccator for

four days prior to weighing (to generate a rehydration curve), and then wait an additional four days before dehydrating and weighing the next sample. Therefore, it was desired to know if several samples could be placed in the desiccator and weighed sequentially (i.e., without waiting four days before weighing the next sample), assuming the desiccator was immediately put back under vacuum once one sample was removed. In theory, opening and closing the desiccator several times could cause the polymers in the desiccator to absorb some moisture and not be fully dehydrated when they were weighed for generation of rehydration curves. Therefore, a separate experiment was conducted to determine if opening and closing the desiccator affected the state of rehydration of the polymers. These tests were called the “Open-Close Trials” and they were conducted using a single 2 mil thick (50.8 µm) Kapton HN sample. Kapton HN was chosen for the Open-Close Trials because Kapton can gain up to 4% of its mass with moisture (Ref. 3).

The Open-Close Trials were conducted in five separate tests (trials). In the first trial, the Kapton HN sample was placed in the desiccator and allowed to dehydrate for four days. The desiccator was opened and the sample was removed and a rehydration curve was obtained with mass measurements taken after approximately 2, 3, 5, 10, 20, 30 and 60 minutes of air exposure. This is the ideal rehydration procedure. The sample was then returned to the desiccator and dehydrated for four days. For Trial 2, the desiccator was opened and closed five times, at approximately 11 minute intervals, to simulate removal of five samples. The 11 minute intervals allowed the desiccator to pump down to 20 Pa (150 mTorr) or less. Then the desiccator was opened again (for the 6th time), the sample removed, and the sample was periodically weighed to generate a rehydration curve. The process of obtaining rehydration curves after opening and closing the desiccator six times was repeated 3 additional times (Trials 3, 4 and 5) and the data was graphed for each trial. These curves were then compared to the curve of the sample when it was removed immediately (Trial 1).

Rehydration Data The samples were placed in a vacuum desiccator maintained at a pressure of 60-100 mTorr

with a mechanical roughing pump, and dehydrated for a minimum of four days. Once a sample was ready to be weighed, it was removed from the desiccator and the desiccator was immediately put back under vacuum to ensure that remaining samples returned to a fully-dehydrated state. The exact times that the desiccator was opened and closed were recorded.

Mass measurements were taken of each polymer sample eight times (or more if needed) after increasingly long time intervals, for example after 1, 2, 3, 8, 18, 38, 68 and 128 minutes. The time was measured from the time air was initially allowed to flow into the desiccator (it took about 50 seconds for the desiccator to get to atmospheric pressure). Each data point on the curve represents the average of three measurements taken starting at the time recorded. The balance was re-zeroed between each measurement to ensure accuracy for every set of measurements. The temperature and humidity in the laboratory were noted for each hydration data set.

Data that was documented included the time it took to get to a fully hydrated mass, the total mass gain (in mg) and the percent of mass increase for each polymer. The highest point on the rehydration curve was used as the final mass, and the initial mass was determined by back-extrapolating the first three mass readings to time zero to get a theoretical fully-dehydrated mass. An example of a linear back extrapolation is provided in Figure 4. The percent mass increase was calculated from the initial (back-extrapolated) and final mass values.

NASA/TM—2019-220063 7

Figure 4. Kapton H (2-E5-30) linear back extrapolation.

Dehydration Data To verify that a rehydration curve approximates a dehydration curve, 2 mil thick Kapton HN

was used for a dehydration-rehydration comparison. To obtain a dehydration curve, eight one-inch diameter samples of Kapton HN were cut from a sheet of film using a bow-punch and an arbor press. The mass for each sample was obtained by taking three mass measurements and averaging the data. This was the mass value for the sample with zero time in the desiccator (Sample 1). Then Sample 2 was placed into the desiccator and left under vacuum for 1 minute. It was then removed and weighed (an average of 3 readings) to obtain a 1 minute dehydration mass. Additional samples were placed in the desiccator and then removed and weighed after 2, 7, 17, 37, 67, and 127 minutes. The change in mass from the original, non-dehydrated mass, was determined and the data was graphed versus time in the desiccator and compared with a rehydration curve of 2 mil Kapton HN.

Results and Discussion

Dehydration vs. Rehydration Data Dehydration and rehydration curves for 2 mil thick Kapton HN are provided in Figure 5. These

curves are plotted as change in mass versus time, because different samples were used and the starting mass varied. As can be seen, the curves are on the same order of magnitude, and approximate each other. But, there is more uncertainty, or error, in the dehydration data for the short dehydration times (1 - 3 minutes). Whereas the rehydration data, which is easier and quicker to obtain, provides a smoother, more reliable curve for short times. This data shows that that rehydration curves are better indicators of the duration necessary for dehydration.

y = 0.0315x + 61.265R² = 0.9992

61.26

61.28

61.30

61.32

61.34

61.36

61.38

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

Mas

s (m

g)

Time (min)

NASA/TM—2019-220063 8

Figure 5. Dehydration and rehydration mass change curves for 2 mil Kapton HN.

Open-Close Trials Figure 6 provides the rehydration curves for the Open-Close Trial tests of Kapton HN. The

Trial 1 curve (red) is for the ideal procedure, where the sample’s rehydration curve was obtained directly after four days of dehydration. The data obtained from the samples that were removed after five simulated sample removals from the desiccator, are listed as Trials 2-5, and are plotted with the Trial 1 curve. There is some variability in initial mass, but, the similarity of the shape of the five curves shows that previous opening and closing of the desiccator, does not significantly affect the rehydration data. Therefore, it was concluded that numerous samples could be put into a desiccator and tested for rehydration as long the desiccator is immediately put back under vacuum once a sample is removed.

0

0.2

0.4

0.6

0.8

1

0 40 80 120

Cha

nge

in m

ass

(mg)

Time (min)

Change in mass (dehydration)Change in mass (rehydration)

NASA/TM—2019-220063 9

Figure 6. “Open-Close Trials” series of rehydration curves using one Kapton HN sample.

Rehydration Data The rehydration data for the PEACE polymers are provided in Table 2. The table includes the

MISSE serial number, the material and material abbreviation, the sample thickness, the duration over which the rehydration data was collected, the total mass gain (in mg) and the percent mass increase for the duration the data was collected. The rehydration curves are provided in Figures 7 through Figure 50.

As can be seen in Table 2, the polymers displayed a very wide range of moisture absorption, hence the hygroscopic nature of the polymers varied greatly. Some of the polymers, such as PP, PVDC and UHMWPE had very little moisture absorption. The percent mass increase was ≤ 0.032% for these polymers. This was also true for the only non-polymer, pyrolytic graphite, which had a negligible moisture absorption (0.001% mass increase). Fourteen samples had an increase in mass of greater than 1%. And, numerous samples had large moisture absorption including PE, PMMA, PPPA, PA 6, PA 66, Upilex-S, PMR-15 and PTFE. These samples had ≥ 2% increase in mass. The polymer with the greatest mass increase was PBI with a total mass increase of 7.14%. As can be seen in the rehydration curves, the samples absorbed moisture and gained most of their mass within approximately 1 hour, or 60 minutes. It should also be pointed out that not all polymers were fully rehydrated in the time period that data was collected. This particularly noticeable in the graphs of polyamide 6 (PA 6, Figure 28) and polyamide 66 (PA 66, Figure 29).

37.90

37.95

38.00

38.05

38.10

38.15

38.20

38.25

38.30

0 10 20 30 40 50 60 70 80

Mas

s (m

g)

Time (min)

Trial 1: weighed immediatelyTrial 2: weighed after opened/closed 6XTrial 3: weighed after opened/closed 6XTrial 4: weighed after opened/closed 6XTrial 5: weighed after opened/closed 6X

NASA/TM—2019-220063 10

Table 2. Rehydration Data for the PEACE Polymers. MISSE 2 Serial # Material Abbrev. Thickness

(mils)

Time Interval

(min)

Mass Gain (mg)

% Mass Increase

2-E5-6 Acrylonitrile butadiene styrene ABS 5 72.0 0.215 0.314 2-E5-7 Cellulose acetate CA 2 133.0 0.076 0.246 2-E5-8 Poly-(p-phenylene terephthalamide) PPDT 2.2 128.0 0.131 0.749 2-E5-9 Polyethylene PE 2 128.0 1.212 4.736

2-E5-10 Polyvinyl fluoride PVF 1 128.0 0.009 0.087 2-E5-11 Crystalline polyvinylfluoride w/white pigment PVF 1 127.2 0.270 0.990 2-E5-12 Polyoxymethylene; acetal; polyformaldehyde POM 10 193.0 0.311 0.147 2-E5-13 Polyacrylonitrile PAN 2 72.0 0.173 0.663 2-E5-14 Allyl diglycol carbonate ADC 31 238.0 0.351 0.103 2-E5-15 Polystyrene PS 2 69.0 0.020 0.108 2-E5-16 Polymethyl methacrylate PMMA 2 128.0 0.454 2.591 2-E5-17 Polyethylene oxide PEO 29 1200.0 1.965 0.690 2-E5-18 Poly(p-phenylene-2 6-benzobisoxazole) PBO 1 128.0 0.141 1.281 2-E5-19 Epoxide or epoxy EP 88-92 4230.0 4.040 0.306 2-E5-20 Polypropylene PP 20 128.0 0.050 0.032 2-E5-21 Polybutylene terephthalate PBT 3 128.0 0.097 0.188 2-E5-22 Polysulfone PSU 2 128.0 0.062 0.196 2-E5-23 Polyurethane PU 2 128.0 0.239 0.689 2-E5-24 Polyphenylene isophthalate PPPA 2 128.0 0.633 3.396 2-E5-25 Pyrolytic graphite PG 80 128.0 0.011 0.001 2-E5-26 Polyetherimide PEI 10 2852.0 0.876 0.695 2-E5-27 Polyamide 6 PA 6 2 126.6 0.863 3.040 2-E5-28 Polyamide 66 PA 66 2 127.8 0.503 1.956 2-E5-29 Polyimide (Clear), CP1 PI 3 128.0 0.262 0.443 2-E5-30 2-E5-33 Polyimide (PMDA), Kapton H PI 5 128.0 0.445 0.726

N/A Polyimide (PMDA), Kapton H PI 2 147.0 0.149 0.860 2-E5-31 Polyimide (PMDA), Kapton HN PI 5 72.0 0.391 1.033 2-E5-32 Polyimide (BPDA), Upilex-S PI 1 128.0 0.424 2.960 2-E5-34 High temperature polyimide resin PI 12-14 2862.0 3.833 2.084 2-E5-35 Polybenzimidazole PBI 2 129.8 2.031 7.141 2-E5-36 Polycarbonate PC 10 69.0 0.226 0.153 2-E5-37 Polyetheretherketone PEEK 3 70.0 0.123 0.259 2-E5-38 Polyethylene terephthalate PET 2 133.7 0.077 0.206 2-E5-39 Chlorotrifluoroethylene CTFE 5 128.0 0.526 0.558 2-E5-40 Ethylene-chlorotrifluoroethylene ECTFE 3 128.0 0.201 0.525 2-E5-41 Tetrafluorethylene-ethylene copolymer ETFE 3 129.0 0.095 0.180 2-E5-42 Fluorinated ethylene propylene FEP 2 128.0 0.493 1.013 2-E5-43 Polytetrafluoroethylene PTFE 2 129.0 1.698 2.802 2-E5-44 Perfluoroalkoxy PFA 2 128.0 0.449 0.819 2-E5-45 Amorphous fluoropolymer AF 2 128.1 0.371 0.223 2-E5-46 Polyvinylidene fluoride PVDF 3 128.0 0.110 0.163

N/A Cellulose nitrate CN 5 128.000 0.278 1.021 N/A Polyvinylidene chloride PVDC 2 129.120 0.010 0.020 N/A Ultra-high molecular weight polyethylene UHMWPE 10 129.000 0.027 0.024 Note: Not all polymers were fully rehydrated in the time period the data was collected.

NASA/TM—2019-220063 11

Figure 7. Rehydration curve for ABS (2-E5-6).

Figure 8. Rehydration curve for CA (2-E5-7).

68.50

68.55

68.60

68.65

68.70

68.75

0 10 20 30 40 50 60 70 80

Mas

s (m

g)

Time (min)

30.91

30.92

30.93

30.94

30.95

30.96

30.97

30.98

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140

Mas

s (m

g)

Time (min)

NASA/TM—2019-220063 12

Figure 9. Rehydration curve for PPDT (2-E5-8).

Figure 10. Rehydration curve for PE (2-E5-9).

17.50

17.52

17.54

17.56

17.58

17.60

17.62

17.64

0 10 20 30 40 50 60 70 80 90 100 110 120 130

Mas

s (m

g)

Time (min)

25.80

25.90

26.00

26.10

26.20

26.30

26.40

26.50

26.60

26.70

26.80

26.90

0 10 20 30 40 50 60 70 80 90 100 110 120 130

Mas

s (m

g)

Time (min)

NASA/TM—2019-220063 13

Figure 11. Rehydration curve for clear Tedlar (2-E5-10).

Figure 12. Rehydration curve for White Tedlar (2-E5-11).

10.360

10.362

10.364

10.366

10.368

0 20 40 60 80 100 120

Mas

s (m

g)

Time (min)

27.25

27.30

27.35

27.40

27.45

27.50

27.55

0 20 40 60 80 100 120 140

Mas

s (m

g)

Time (min)

NASA/TM—2019-220063 14

Figure 13. Rehydration curve for Delrin (2-E5-12).

Figure 14. Rehydration curve for PAN (2-E5-13).

212.10

212.15

212.20

212.25

212.30

212.35

212.40

212.45

0 20 40 60 80 100 120 140 160 180 200

Mas

s (m

g)

Time (min)

26.14

26.16

26.18

26.20

26.22

26.24

26.26

26.28

26.30

0 10 20 30 40 50 60 70 80

Mas

s (m

g)

Time (min)

NASA/TM—2019-220063 15

Figure 15. Rehydration curve for ADC (2-E5-14).

Figure 16. Rehydration curve for PS (2-E5-15)

339.40

339.48

339.56

339.64

339.72

339.80

0 20 40 60 80 100 120 140 160 180 200 220 240

Mas

s (m

g)

Time (min)

18.590

18.595

18.600

18.605

18.610

0 10 20 30 40 50 60 70 80

Mas

s (m

g)

Time (min)

NASA/TM—2019-220063 16

Figure 17. Rehydration curve for PMMA (2-E5-16).

Figure 18. Rehydration curve for PEO (2-E5-17).

17.50

17.55

17.60

17.65

17.70

17.75

17.80

17.85

17.90

17.95

18.00

18.05

18.10

0 20 40 60 80 100 120 140

Mas

s (m

g)

Time (min)

284.90

285.10

285.30

285.50

285.70

285.90

286.10

286.30

286.50

286.70

286.90

287.10

0 25 50 75 100 125 150

Mas

s (m

g)

Time (min)

NASA/TM—2019-220063 17

Figure 19. Rehydration curve for PBO (2-E5-18).

Figure 20. Rehydration curve for EP (2-E5-19).

11.02

11.04

11.06

11.08

11.10

11.12

11.14

11.16

0 20 40 60 80 100 120

Mas

s (m

g)

Time (min)

1321.55

1321.85

1322.15

1322.45

1322.75

0 50 100 150

Mas

s (m

g)

Time (min)

NASA/TM—2019-220063 18

Figure 21. Rehydration curve for PP (2-E5-20)

Figure 22. Rehydration curve for PBT (2-E5-21).

156.505

156.515

156.525

156.535

156.545

156.555

0 20 40 60 80 100 120

Mas

s (m

g)

Time (min)

51.73

51.74

51.75

51.76

51.77

51.78

51.79

51.80

51.81

51.82

51.83

51.84

0 10 20 30 40 50 60 70 80 90 100 110 120 130

Mas

s (m

g)

Time (min)

NASA/TM—2019-220063 19

Figure 23. Rehydration curve for PSU (2-E5-22).

Figure 24. Rehydration curve for PU (2-E5-23).

31.68

31.69

31.69

31.70

31.71

31.72

31.73

31.73

31.74

0 20 40 60 80 100 120 140

Mas

s (m

g)

Time (min)

34.60

34.65

34.70

34.75

34.80

34.85

34.90

0 20 40 60 80 100 120

Mas

s (m

g)

Time (min)

NASA/TM—2019-220063 20

Figure 25. Rehydration curve for PPPA (2-E5-24).

Figure 26. Rehydration curve for PG (2-E5-25).

18.66

18.76

18.86

18.96

19.06

19.16

19.26

19.36

0 25 50 75 100 125 150

Mas

s (m

g)

Time (min)

2109.255

2109.258

2109.260

2109.263

2109.265

2109.268

2109.270

0 20 40 60 80 100 120 140

Mas

s (m

g)

Time (min)

NASA/TM—2019-220063 21

Figure 27. Rehydration curve for PEI (2-E5-26)

Figure 28. Rehydration curve for PA 6 (2-E5-27).

126.0

126.2

126.4

126.6

126.8

127.0

0 500 1000 1500 2000 2500 3000

Mas

s (m

g)

Time (min)

28.47

28.57

28.67

28.77

28.87

28.97

29.07

29.17

29.27

0 20 40 60 80 100 120 140

Mas

s (m

g)

Time (min)

NASA/TM—2019-220063 22

Figure 29. Rehydration curve for PA 66 (2-E5-28).

Figure 30. Rehydration curve for CP 1 (2-E5-29).

25.65

25.75

25.85

25.95

26.05

26.15

26.25

0 20 40 60 80 100 120 140

Mas

s (m

g)

Time (min)

59.13

59.16

59.19

59.22

59.25

59.28

59.31

59.34

59.37

0 10 20 30 40 50 60 70 80 90 100 110 120 130

Mas

s (m

g)

Time (min)

NASA/TM—2019-220063 23

Figure 31. Rehydration curve for 5 mil Kapton H (2-E5-30 & 2-E5-33).

Figure 32. Rehydration curve for 2 mil Kapton H (not flown on MISSE 2).

61.25

61.30

61.35

61.40

61.45

61.50

61.55

61.60

61.65

61.70

61.75

0 20 40 60 80 100 120 140

Mas

s (m

g)

Time (min)

17.32

17.34

17.36

17.38

17.40

17.42

17.44

17.46

17.48

17.50

0 25 50 75 100 125 150

Mas

s (m

g)

Time (min)

NASA/TM—2019-220063 24

Figure 33. Rehydration curve for Kapton HN (2-E5-31).

Figure 34. Rehydration curve for Upilex-S (2-E5-32).

37.90

37.95

38.00

38.05

38.10

38.15

38.20

38.25

38.30

0 10 20 30 40 50 60 70 80

Mas

s (m

g)

Time (min)

14.30

14.35

14.40

14.45

14.50

14.55

14.60

14.65

14.70

14.75

14.80

0 20 40 60 80 100 120 140

Mas

s (m

g)

Time (min)

NASA/TM—2019-220063 25

Figure 35. Rehydration curve for PMR-15 (2-E5-34).

Figure 36. Rehydration curve for PBI (2-E5-35).

183.95

184.45

184.95

185.45

185.95

186.45

186.95

187.45

187.95

0 500 1000 1500 2000 2500 3000

Mas

s (m

g)

Time (min)

28.45

28.65

28.85

29.05

29.25

29.45

29.65

29.85

30.05

30.25

30.45

30.65

0 20 40 60 80 100 120 140

Mas

s (m

g)

Time (min)

NASA/TM—2019-220063 26

Figure 37. Rehydration curve for PC (2-E5-36).

Figure 38. Rehydration curve for PEEK (2-E5-37).

147.83

147.85

147.87

147.89

147.91

147.93

147.95

147.97

147.99

148.01

148.03

0 10 20 30 40 50 60 70

Mas

s (m

g)

Time (min)

47.56

47.58

47.60

47.62

47.64

47.66

47.68

0 10 20 30 40 50 60 70 80

Mas

s (m

g)

Time (min)

NASA/TM—2019-220063 27

Figure 39. Rehydration curve for PET (2-E5-38).

Figure 40. Rehydration curve for CTFE (2-E5-39).

37.34

37.35

37.36

37.37

37.38

37.39

37.40

37.41

37.42

0 20 40 60 80 100 120 140

Mas

s (m

g)

Time (min)

94.250

94.399

94.548

94.697

94.846

0 10 20 30 40 50 60 70 80 90 100 110 120 130

Mas

s (m

g)

Time (min)

NASA/TM—2019-220063 28

Figure 41. Rehydration curve for ECTFE (2-E5-40).

Figure 42. Rehydration curve for ETFE (2-E5-41).

38.30

38.32

38.34

38.36

38.38

38.40

38.42

38.44

38.46

38.48

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140

Mas

s (m

g)

Time (min)

52.68

52.69

52.70

52.71

52.72

52.73

52.74

52.75

52.76

52.77

52.78

0 10 20 30 40 50 60 70 80 90 100 110 120 130

Mas

s (m

g)

Time (min)

NASA/TM—2019-220063 29

Figure 43. Rehydration curve for Teflon FEP (2-E5-42).

Figure 44. Rehydration curve for PTFE (2-E5-43).

48.65

48.70

48.75

48.80

48.85

48.90

48.95

49.00

49.05

49.10

49.15

0 20 40 60 80 100 120 140

Mas

s (m

g)

Time (min)

60.80

61.00

61.20

61.40

61.60

61.80

62.00

62.20

62.40

0 20 40 60 80 100 120 140

Mas

s (m

g)

Time (min)

NASA/TM—2019-220063 30

Figure 45. Rehydration curve for PFA (2-E5-44).

Figure 46. Rehydration curve for Teflon AF (2-E5-45).

54.70

54.80

54.90

55.00

55.10

55.20

55.30

55.40

0 20 40 60 80 100 120

Mas

s (m

g)

Time (min)

166.25

166.30

166.35

166.40

166.45

166.50

166.55

166.60

166.65

0 20 40 60 80 100 120 140

Mas

s (m

g)

Time (min)

NASA/TM—2019-220063 31

Figure 47. Rehydration curve for PVDF (2-E5-46).

Figure 48. Rehydration curve for CN.

67.62

67.63

67.65

67.66

67.68

67.69

67.71

67.72

67.74

0 10 20 30 40 50 60 70 80 90 100 110 120 130

Mas

s (m

g)

Time (min)

23.50

23.60

23.70

23.80

0 20 40 60 80 100 120

Mas

s (m

g)

Time (min)

NASA/TM—2019-220063 32

Figure 49. Rehydration curve for Saran.

Figure 50. Rehydration curve for UHMWPE.

45.98

45.98

45.99

45.99

45.99

45.99

45.99

0 20 40 60 80 100 120 140

Mas

s (m

g)

Time (min)

112.16

112.16

112.17

112.17

112.17

112.18

112.18

112.18

112.18

112.19

112.19

0 10 20 30 40 50 60 70 80 90 100 110 120 130

Mas

s (m

g)

Time (min)

NASA/TM—2019-220063 33

Using the data from the rehydration curves the pre-flight and post-flight mass procedures for the MISSE 2 PEACE Polymers experiment were developed. Based the data of the Open-Close Trials for Kapton H, it was concluded numerous samples could be dehydrated together with mass measurements made sequentially. The flight samples were dehydrated in a vacuum desiccator maintained at a pressure of 8.0 - 13.3 Pa (60-100 mTorr) with a mechanical roughing pump. Typically, five flight samples and their corresponding back-up samples were placed together in a desiccator (a total of 10 groups of samples). The sets of samples were placed in the desiccator in a particular order and left under vacuum for a minimum of 4 days.

Many of thin film polymers appear to have gained most of their mass within a couple hours based on the rehydration data. But, not all polymers were fully rehydrated in the time period that the data was collected. This was particularly true for both polyamide 6 (PA 6) and polyamide 66 (PA 66). Therefore, it was determined that the flight samples should be dehydrated for a minimum of 4 days (96 hours) to help ensure that the samples were fully dehydrated prior to the mass being obtained. The vacuum desiccator was put under vacuum immediately after a sample was removed to keep the additional samples dehydrated. The time at which the sample was first exposed to air was recorded along with the times at which it was weighed. A total of 3 mass readings were obtained and averaged. The total time it took to obtain the three readings, starting from the time air was let into the desiccator, was typically five minutes. Records of the following were kept: the sequence of sample weighing, the number of samples in each set, the time under vacuum prior to weighing, the temperature and humidity in the room, the time air was let into the desiccator and the time a sample was taken out of the desiccator, the time of each weighing and the mass. The same procedure and sequence was repeated with the same samples post-flight.

Conclusions The primary objective of the MISSE 2 PEACE Polymers experiment was to determine the AO

Ey of a wide variety of polymers exposed to the LEO space environment. The Ey values were determined based on mass loss measurements. Because many polymeric materials are hygroscopic, pre-flight and post-flight mass measurements were obtained using dehydrated samples. To maximize the accuracy of the mass measurements dehydration data for each of the polymers was desired. A comparison of dehydration and rehydration data showed that rehydration data mirrors dehydration data, and is easier and more reliable to obtain. In addition, Open-Close Trial tests were conducted and showed that multiple samples could be dehydrated and tested sequentially, as long as the desiccator was returned under vacuum as soon as a sample was removed.

Rehydration curves of 43 different polymers and pyrolytic graphite were obtained. The polymers displayed a wide range of moisture absorption, hence the hygroscopic nature of the polymers varied greatly. Some of the polymers, such as PP, PVDC and UHMWPE had very little moisture absorption (≤ 0.032%). Pyrolytic graphite had negligible moisture absorption (0.001% mass increase). Fourteen samples had an increase in mass of greater than 1%. And, numerous samples had large moisture absorption (≥ 2%) including PE, PMMA, PPPA, PA 6, PA 66, Upilex-S, PMR-15 and PTFE. The polymer with the greatest mass increase in the duration the data was collected was PBI with a total mass increase of 7.14%. Many of thin film polymers appear to have gained most of their mass within a couple hours based on the rehydration data. But, not all polymers were fully rehydrated in the time period that the data was collected. This information was used to determine the best pre-flight and post-flight mass procedures for the MISSE 2 PEACE Polymers experiment, including dehydrating the samples for a minimum of 96 hours prior to measuring the mass of the samples.

NASA/TM—2019-220063 34

References 1. de Groh, K. K. Banks, B. A. McCarthy, C. E. Rucker, R. N. Roberts L. M. and Berger, L. A.,

“MISSE 2 PEACE Polymers Atomic Oxygen Erosion Experiment on the International Space Station,” High Performance Polymers 20 (2008) 388-409 (Rev).

2. NASA Technical Handbook, Spacecraft Polymers Atomic Oxygen Durability Handbook (NASA-HDBK-6024), Revalidated 2017. Authors: K. K. de Groh, B. A. Banks and C. E. McCarthy.

3. DuPont, “DuPont Kapton Polyimide Film General Specifications,” http://www.dupont.com/content/dam/dupont/products-and-services/membranes-and-films/polyimde-films/documents/DEC-Kapton-general-specs.pdf, accessed February 20, 2018.