Reversible bonding via exchange reactions following atomic oxygen and proton exposure

Abstract

Future space structures have several design concerns, among them are larger physical scale and changes in mission profile over their potentially multi-decade operational lifetimes. A reversible adhesive suitable for in-space assembly could simplify these efforts. Key requirements for such applications are that: (1) the reversible adhesive has a sufficiently high glass transition temperature (Tg) to provide mechanical strength throughout the day/night cycle, (2) the adhesive schema is truly reversible in a vacuum environment and can be executed in space, and (3) the reversible adhesive can survive significant durations under the elevated radiation flux of low earth orbit (LEO) and mission locations. This study examines a high Tg vitrimer-type reversible adhesive known as aromatic thermosetting copolyester (ATSP) under two radiation species (atomic oxygen and protons) at flux levels intended to represent equivalent exposure in LEO for 1, 10, and 50 years. Surface morphology studies were conducted via 3 D laser profilometry and found no change in morphology following exposure. Reversible adhesive experiments were conducted and found consistent performance after atomic oxygen and proton exposures up to 50 years. Raman spectroscopy likewise found no obvious changes in surface chemistry. A consistent activation energy for bond exchange was observed between unexposed films and films exposed to 1 and 10 years of LEO-equivalent proton exposure. Similarly, thermogravimetry found consistent performance in the thermal stability of ATSP polymer films before and after 1 and 10 years of LEO-equivalent proton exposure. Results suggest that ATSP represents a viable option for a reversible adhesive for in-space assembly.

Keywords:

• Vitrimers
• in-space assembly
• reversible adhesive

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This research work was supported by the NASA SBIR program under grant contract 80NSSC18C0040. The SEM and 3D profilometer analysis was carried out at the Materials Research Laboratory Central Research Facilities at the University of Illinois. Jacob Meyer, Pixiang Lan, and James Economy serve as employees of ATSP Innovations which owns intellectual property on this technology.