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Evaluation of the Effects of Hydrogen Peroxide on Common Aircraft Electrical Materials

Study aims to find a suitable decontaminant/disinfectant/sanitizer that can be used successfully in complex transportation vehicles with no negative impact on sensitive electronic equipment.

Among all of the large-scale disinfection and/or decontamination technologies available, vaporized hydrogen peroxide (VHP®) is of particular interest due to its rapid sterilization, easy usage, intrinsic environmental friendliness (i.e. simple by-products composed of only water and oxygen), and compatibility with many materials and systems.

Wire Board (Figure a), Interdigitated Board (Figure b), Pad Board (Figure c), Active Board (Figure d), and Aviation (MILSPEC) Wire (Figure e)

VHP® technology has been investigated for possible usage in aircraft applications. These studies used vaporized hydrogen peroxide concentrations in the range of 150 - 600 ppm and cycle times of 80 - 120 min. Maximum concentrations of hydrogen peroxide vapor were carefully controlled to avoid condensation in cool locations within the aircraft cabins. Although these studies did not evaluate the compatibility of the various cabin materials with exposure to vaporized hydrogen peroxide, analysis of the collected data showed that VHP® did not seem to have any visible effect on the materials.

A typical VHP® process cycle consists of an initial dehumidification step, then a conditioning phase followed by the actual sanitization/decontamination process. Finally, an aeration phase is employed to remove residual hydrogen peroxide vapor. During the dehumidification phase, warm, dry air flows into the enclosure to lower the relative humidity to less than 10%. This allows a higher concentration of hydrogen peroxide vapor to be injected into the enclosure without causing condensation. Hydrogen peroxide liquid concentrate (35% liquid H2O2 with a pH ~ 3) is then flash vaporized and injected into the enclosure during the initial conditioning and sanitization/decontamination phases. The purpose of the conditioning phase is to rapidly increase the hydrogen peroxide concentration to minimize the overall cycle time.

During the sanitization/decontamination phase, a steady concentration of hydrogen peroxide vapor (typically 250 - 450 ppm) is maintained. This produces the desired sanitization/decontamination effect that is often measured by the 6-log kill (i.e. 106 reduction) of a commercial biological indicator (BI) spore population of Geobacillus stearothermophilus. Once the sanitization/ decontamination phase is completed, the enclosure is aerated with fresh air while any residual hydrogen peroxide vapor breaks down into environmentally benign water and oxygen.

Many polymeric materials are known to be susceptible to absorption of moisture. The small water molecules diffuse into the polymer matrix and force apart the polymer macromolecules, causing swelling. Increases in the distance between the polymer chains reduce the strength of the secondary intermolecular bonds and increase the softness and ductility of the polymer. However, the highly cross-linked epoxies used in aerospacegrade fiber composites minimize moisture absorption. Thus, these materials exhibit good resistance to degradation in wet environments.

While molecules of H2O2 vapor should be absorbed even less by epoxies than H2O molecules, the intermolecular crosslinks might be degraded by oxidation from the hydrogen peroxide. The extensive usage of fiber/epoxy composites in aerospace structures and avionics dictates that the compatibility of these materials with hydrogen peroxide vapor be examined. Therefore, a decision was made to design dummy and active printed circuit boards. The dummy circuit board had no active components. The active board had operational components including voltage level converters, a microcontroller, resistors, capacitors, and connectors. In addition to these boards, avionics wires were also used as test samples, as shown in the accompanying figure.

This work was done by Sin Ming Loo, Josh Kiepert, Derek Klein and Michael Pook of Boise State University; Shih-Feng Chou and Tony Overfelt of Auburn University; and Jean Watson for the Federal Aviation Administration. FAA-0002

Topics:
Aeronautics Aerospace Aircraft Aviation Board-Level Electronics Cleaning Composites Electrical systems Electronic Components Electronics Electronics & Computers Materials Materials properties Medical equipment and supplies Medical, health and wellness Medical, health, and wellness Oxygen Sterilization Transportation Vehicles Water
This Brief includes a Technical Support Package (TSP).
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Evaluation of the Effects of Hydrogen Peroxide on Common Aircraft Electrical Materials

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    Aerospace & Defense Technology Magazine

    This article first appeared in the February, 2020 issue of Aerospace & Defense Technology Magazine (Vol. 5 No. 1).

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    Overview

    The document titled "Evaluation of the Effects of Hydrogen Peroxide on Common Aircraft Electrical Materials" is a technical report that investigates the compatibility of vaporized hydrogen peroxide (VHP®) as a disinfectant for aircraft avionics and electrical materials. The study is motivated by the need for effective decontamination methods in transportation vehicles, particularly in the context of potential chemical or biological contamination.

    The report begins with an introduction to the use of hydrogen peroxide in the medical field and its potential application in disinfecting transportation vehicles, including aircraft. It emphasizes the necessity of evaluating the effects of VHP® on various aircraft materials, particularly avionics wires and printed circuit boards, to ensure their integrity and functionality after exposure.

    The methodology section outlines the experimental setup used to test the effects of VHP® on aviation wire insulation and circuit boards. High-voltage stress tests were conducted on aviation wire samples to assess insulation breakdown when exposed to VHP®. The tests involved applying approximately 18.5 kV RMS at 60 Hz to sections of aviation wire, with monitoring for insulation failure indicated by current spikes.

    Results from the tests are discussed in detail, revealing the impact of VHP® exposure on the physical and chemical properties of the materials tested. The report includes findings on weight changes, chemical analysis, and the overall performance of the materials post-exposure. It highlights the importance of understanding how VHP® interacts with these materials to prevent potential failures in aircraft systems.

    The conclusions drawn from the study indicate that while VHP® can be an effective decontaminant, its effects on aircraft electrical materials must be carefully considered. The report suggests that further research is needed to fully understand the long-term implications of VHP® exposure on avionics and to establish guidelines for safe use in aircraft maintenance and decontamination processes.

    Overall, the document serves as a preliminary evaluation of the compatibility of hydrogen peroxide with aircraft electrical materials, providing valuable insights for the aviation industry as it seeks to implement effective disinfection protocols while ensuring the safety and reliability of aircraft systems.

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