Mechanistic Studies of Atomic Oxygen Reactions with Polymers and Combined Effects with Vacuum Ultraviolet Light

MRS Bulletin ◽  
2010 ◽  
Vol 35 (1) ◽  
pp. 35-40 ◽  
Author(s):  
Masahito Tagawa ◽  
Timothy K. Minton
Keyword(s):  
Atomic Oxygen ◽  
Vacuum Ultraviolet ◽  
Uv Light ◽  
Synergistic Effects ◽  
Low Earth Orbit ◽  
Point Of View ◽  
Experimental Results ◽  
Space Environment ◽  
Combined Effects ◽  
The Individual

AbstractThis article focuses on mechanistic aspects of hyperthermal atomic oxygen reactions with polymers, which are the major contributor to material degradation in low Earth orbit. Due to the importance of well-controlled experiments in the understanding of the reaction mechanisms, ground-based experimental results obtained by a hyperthermal atomic oxygen beam generated by laser detonation facilities are mainly surveyed. Combined effects of atomic oxygen and vacuum ultraviolet (VUV) light on fluorinated polymers are also described. Such combined effects of hyperthermal atomic oxygen and VUV light are important not only from a fundamental point of view but also for engineering purposes (i.e., methodology for ground-based space environmental simulation). The VUV-sensitive polymers, poly(methyl methacrylate), and Teflon fluorinated ethylene-propylene do not show significant synergistic effects. Instead, the effect of combining atomic oxygen and VUV light produces erosion of the polymer that is the sum of the erosion caused by atomic oxygen and UV light acting individually. The experimental results suggest that material erosion in a complicated space environment may be quantitatively predicted if the erosion yields caused by the individual action of atomic oxygen and VUV light are known.

Atomic Oxygen Resistant Films for Multi-Layer Insulation

2000 ◽  
Vol 12 (1) ◽  
pp. 113-123 ◽  
Author(s):  
Peter Schuler ◽  
H Bob Mojazza ◽  
Ross Haghighat
Keyword(s):  
Atomic Oxygen ◽  
Vacuum Ultraviolet ◽  
Thermal Control ◽  
Radiation Stability ◽  
Low Earth Orbit ◽  
Space Environment ◽  
Advanced Materials ◽  
Validation Tests ◽  
Atomic Oxygen Erosion

A series of advanced polymer films from Triton Systems is being developed to meet the challenges of harsh space environmental effects, lighter weight requirements and superior thermal control performance demands. With support from NASA, Triton Systems Inc has developed advanced new materials for thermal control films with exceptional properties and durability in the space environment. These films known as TOR™ and TOR-LM™ are amber coloured, mechanically sound, produced in continuous rolls and have undergone substantial ground-based simulation and confirming space validation tests. These films are highly resistant to atomic oxygen erosion, and have excellent vacuum ultraviolet radiation stability in ground-based simulation tests. Two applications for these films include large inflatable structures that are either deployed in low earth orbit (LEO) or travel through a LEO orbit into higher orbits, and as outer metallized layers in multi-layer insulation (MLI) blankets. This paper discusses the processing of these advanced materials into thin films, metallization of the films and characterization of their environmental durability as well as other physical, optical, thermal and mechanical properties.

scholarly journals The Effect of Low Earth Orbit Atomic Oxygen Exposure on Phenylphosphine Oxide-Containing Polymers

2000 ◽  
Vol 12 (1) ◽  
pp. 43-52 ◽  
Author(s):  
John W Connell
Keyword(s):  
Thin Film ◽  
Atomic Oxygen ◽  
Low Earth Orbit ◽  
Space Environment ◽  
Earth Orbit ◽  
Cooperative Effort ◽  
Flight Experiment ◽  
Oxygen Exposure ◽  
Atomic Oxygen Exposure ◽  
Phenylphosphine Oxide

Thin films of phenylphosphine oxide-containing polymers were exposed to low Earth orbit aboard a space shuttle flight (STS-85) as part of flight experiment designated Evaluation of Space Environment and Effects on Materials (ESEM). This flight experiment was a cooperative effort between the NASA Langley Research Center (LaRC) and the National Space Development Agency of Japan (NASDA). The thin-film samples described herein were part of an atomic oxygen exposure (AOE) experiment and were exposed to primarily atomic oxygen (∼1×1019 atoms cm−2). The thin-film samples consisted of three phosphine oxide-containing polymers (arylene ether, benzimidazole and imide). Based on post-flight analyses using atomic force microscopy, x-ray photo-electron spectroscopy and weight loss data, it was found that the exposure of these materials to atomic oxygen (AO) produces a phosphorus oxide layer on the surface of the samples. Earlier work has shown that this layer provides a barrier towards further attack by AO. Consequently, these materials do not exhibit linear erosion rates which is in contrast with most organic polymers. Qualitatively, the results obtained from these analyses compare favourably with those obtained from samples exposed to AO and/or an oxygen plasma in ground-based exposure experiments. The results of the low Earth orbit AO exposure on these materials will be compared with those of ground-based exposure to AO.

Individual and Combined Effects of Vanillin and Potassium Sorbate on Penicillium digitatum, Penicillium glabrum, and Penicillium italicum Growth

1999 ◽  
Vol 62 (5) ◽  
pp. 541-542 ◽  
Author(s):  
B. MATAMOROS-LEÓN ◽  
A. ARGAIZ ◽  
A. LÓPEZ-MALO
Keyword(s):  
Water Activity ◽  
Inhibitory Concentration ◽  
Synergistic Effects ◽  
Potato Dextrose Agar ◽  
Penicillium Digitatum ◽  
Potassium Sorbate ◽  
Combined Effects ◽  
Fractional Inhibitory Concentration ◽  
Penicillium Italicum ◽  
The Individual

The individual and combined effects of potassium sorbate and vanillin concentrations on the growth of Penicillium digitatum, P. glabrum, and P. italicum in potato dextrose agar adjusted to water activity 0.98 and pH 3.5 were evaluated. Inhibitory concentrations of potassium sorbate varied from 150 ppm for P. digitatum to 700 ppm for P. glabrum, and for vanillin from 1,100 ppm for P. digitatum and P. italicum and 1,300 ppm for P. glabrum. Fractional inhibitory concentration (FIC) isobolograms show curves deviated to the left of the additive line. Calculated FIC index varied from 0.60 to 0.84. FIC index as well as FIC isobolograms show synergistic effects on mold inhibition when vanillin and potassium sorbate are applied in combination.

Space Environment Effect on Fluorinated Polymers

2003 ◽  
Vol 792 ◽  
Author(s):  
M. Chipara ◽  
D. L. Edwards ◽  
J. Zaleski ◽  
B. Hoang ◽  
B. Przewoski ◽  
...  
Keyword(s):  
Atomic Oxygen ◽  
Low Earth Orbit ◽  
Space Environment ◽  
Fluorinated Polymers ◽  
Space Applications ◽  
Environment Effect ◽  
Low Altitude ◽  
Low Earth Orbits ◽  
Degradation Of Materials ◽  
Earth Orbits

ABSTRACTThe effects of the space environment on polytetrafluorethylene and some fluorinated polymers, copolymers, and blends are critically reviewed. It is shown that in low altitude orbits such as Low Earth Orbit and Geostationary Orbit the presence of both ionizing radiation and atomic oxygen triggers a synergetic degradation of materials based on fluorinated polymers. The behavior is due to the lability of the in-chain alkyl radical to oxygen attack. It is concluded that fluorinated polymers should not be used as materials for space applications, as long as the mission implies low Earth orbits.

Changes in Tribological Properties of MoS2 Film Exposed to LEO on SM/SEED

2005 ◽  
Author(s):  
Koji Matsumoto ◽  
Masao Akiyama ◽  
Masahito Tagawa ◽  
Kichiro Imagawa
Keyword(s):  
Atomic Oxygen ◽  
Space Station ◽  
Experimental System ◽  
Low Earth Orbit ◽  
Space Environment ◽  
Ultraviolet Rays ◽  
Low Friction ◽  
Environment Exposure ◽  
Mos2 Film ◽  
One Year

Service Module / Space Environment Exposure Device (SM/SEED) is experimental system aboard International Space Station (ISS) to evaluate the degradation of various materials for space application under the Low Earth orbit (LEO) space environment. Three sets of exposure pallets of SM/SEED with the same samples have been exposed to LEO since October 2001. One of the pallets returned to Earth after about one-year exposure. A bonded molybdenum disulfide (MoS2) film was also exposed as a tested material of SM/SEED. The changes in tribological characteristics of the film were examined. And effects of ground-based irradiation with LEO environmental factors (e.g., Atomic Oxygen (AO) and Ultraviolet rays (UV)) were also evaluated. At the beginning of the test, low friction coefficient was observed both in the flight and the AO-irradiated samples. MoO3 was detected from the surface of these samples. A large amount of SiO2 was recognized from the flight sample.

Nonlinear Phenomena in the Mass Loss of Polyimide Films under Hyperthermal Atomic Oxygen Beam Exposure

2001 ◽  
Vol 13 (4) ◽  
pp. 225-234 ◽  
Author(s):  
Hiroshi Kinoshita ◽  
Masahito Tagawa ◽  
Kumiko Yokota ◽  
Nobuo Ohmae
Keyword(s):  
Mass Loss ◽  
Atomic Oxygen ◽  
Large Fraction ◽  
Orbit Space ◽  
Mass Gain ◽  
Polyimide Film ◽  
Low Earth Orbit ◽  
Space Environment ◽  
Nonlinear Phenomena ◽  
Abstraction Reaction

Erosion phenomenon of polyimide film under the hyperthermal atomic oxygen beam exposure, which is a simulated low Earth orbit space environment, has been investigated. The polyimide film was spin-coated on a sensor crystal of a quartz crystal microbalance, and the mass of the film was measured under the atomic oxygen beam exposure. The spin-coated polyimide film which was exposed to a 4.7 eV atomic oxygen beam showed a mass gain at the beginning of the reaction and then steady-state mass loss followed. The experimental results of the mass change was analysed by the computational model, and the results showed that the carbon abstraction rate at the oxygen-adsorbed sites was two orders higher than that at the unoxidized polyimide surface. The computational results suggested that a large fraction of the carbon abstraction reaction occurred in the oxygen-adsorbed site through a Langmuir–Hinshelwood reaction mechanism.

scholarly journals Effect of simultaneous N2 collisions on atomic oxygen-induced polyimide erosion in sub-low Earth orbit: comparison of laboratory and SLATS data

2021 ◽  
Author(s):  
Kumiko Yokota ◽  
Masahito Tagawa ◽  
Yusuke Fujimoto ◽  
Wataru Ide ◽  
Yugo Kimoto ◽  
...  
Keyword(s):  
Atomic Oxygen ◽  
Collision Energy ◽  
Space Shuttle ◽  
Space Station ◽  
Low Earth Orbit ◽  
Experimental Results ◽  
Earth Orbit ◽  
Material Erosion ◽  
Low Altitude

AbstractThe role of N2 in the upper atmosphere on the atomic oxygen (AO)-induced erosion of polyimide in low Earth orbit (LEO) and sub-LEO is investigated through ground-based experiments and flight data. The experiment is performed by adding an Ar beam at the same collision energy as an undecomposed O2 component in the AO beam formed by laser detonation to simulate the physical effect of simultaneous N2 collision in sub-LEO. The Ar beam is added by the dual-pulsed supersonic valve-equipped laser-detonation system developed at Kobe University. The experimental results indicate that the erosion of polyimide in the laser-detonation system is promoted by the presence of O2 and Ar in the beam, corresponding to N2 in the sub-LEO. On-ground experimental results are compared with in-orbit AO measurements. Previous space shuttle, international space station-based exposure experiments, as well as the world’s first real-time sub-LEO material erosion data aboard a super low altitude test satellite (SLATS) orbiting at an altitude of 216.8 km are presented. The SLATS data suggests the presence of an acceleration effect by N2 collision on AO-induced polyimide erosion, as predicted by ground-based experiments.

Synergistic Effects of APOE and CLU May Increase the Risk of Alzheimer’s Disease: Acceleration of Atrophy in the Volumes and Shapes of the Hippocampus and Amygdala

2021 ◽  
Vol 80 (3) ◽  
pp. 1311-1327
Author(s):  
Na An ◽  
Yu Fu ◽  
Jie Shi ◽  
Han-Ning Guo ◽  
Zheng-Wu Yang ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Morphological Changes ◽  
Synergistic Effects ◽  
Combined Effects ◽  
Individual Effects ◽  
The Individual ◽  
Neuroimaging Genetics ◽  
Surface Based Morphometry

Background: The volume loss of the hippocampus and amygdala in non-demented individuals has been reported to increase the risk of developing Alzheimer’s disease (AD). Many neuroimaging genetics studies mainly focused on the individual effects of APOE and CLU on neuroimaging to understand their neural mechanisms, whereas their synergistic effects have been rarely studied. Objective: To assess whether APOE and CLU have synergetic effects, we investigated the epistatic interaction and combined effects of the two genetic variants on morphological degeneration of hippocampus and amygdala in the non-demented elderly at baseline and 2-year follow-up. Methods: Besides the widely-used volume indicator, the surface-based morphometry method was also adopted in this study to evaluate shape alterations. Results: Our results showed a synergistic effect of homozygosity for the CLU risk allele C in rs11136000 and APOE ɛ4 on the hippocampal and amygdalar volumes during a 2-year follow-up. Moreover, the combined effects of APOE ɛ4 and CLU C were stronger than either of the individual effects in the atrophy progress of the amygdala. Conclusion: These findings indicate that brain morphological changes are caused by more than one gene variant, which may help us to better understand the complex endogenous mechanism of AD.

Effects of Atomic Oxygen Irradiation on PDMS/POSS Hybrid Films in Low Earth Orbit Environment

2011 ◽  
Vol 239-242 ◽  
pp. 1368-1371 ◽  
Author(s):  
Mi Mi Song ◽  
Shu Wang Duo ◽  
Ting Zhi Liu
Keyword(s):  
Photoelectron Spectroscopy ◽  
Atomic Oxygen ◽  
Orbit Space ◽  
Low Earth Orbit ◽  
Hybrid Coating ◽  
Space Environment ◽  
Earth Orbit ◽  
Chemical Compositions ◽  
Hybrid Films ◽  
Polyimide Films

In order to improve the atomic oxygen (AO) erosion resistance of polyimide films in low earth orbit space environment, a type PDMS/POSS hybrid coating on polyimide substrate was prepared based on a silanol terminated polydimethylsiloxane (PDMS-OH) and Octakis(trimethylsiloxy)octaprismosilsesquioxane (Q8[Si(CH3)3]8) by copolymerizing process in DMAc solution. The atomic oxygen exposure tests were carried out using a ground-based atomic oxygen simulation facility. The mass loss, surface morphology and surface chemical compositions of PDMS/POSS hybrid films before and after exposure to incremental AO flux were investigated by using microbalance and field emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS), respectively. The data indicated that a silica-rich layer was formed on the surface of the hybrid coating when the coating is exposed to AO flux, which could provide a protective barrier on the surface preventing further degradation of the polymer during extended exposure to AO and obviously improved the AO resistance of polyimide films.

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