Bond exchange reactions and the requirements for an adhesive for in-space assembly

Jacob Meyer
Bond exchange reactions and the requirements for an adhesive for in-space assembly

ATSP personnel Jacob Meyer and Zeba Parkar recently published an article in Adhesives & Sealants Industry magazine outlining the requirements for adhesives to be viable for in-space assembly.  Future space development and exploration prompt the need for multi-stage on-orbit construction as well as reconfigurable and reusable designs due to the expectation of multi-decade service under which changing mission profiles may emerge. 

There are several criteria for a practical reversible adhesive scheme relevant to missions in space: the first is that it is a solid-state process as liquids generally have an unacceptably high vapor pressure in vacuum, which eliminates approaches that rely on uncured polymer or a meltable interstitial phase. The second is that the components of the structure and the reversible adhesive do not experience a glass or melt transition within the range of temperatures experienced by the structure during day/night cycles (-160 to 150°C in LEO) in conditions without thermal controls - this is to avoid introduction of unintential adhesive reversion which may negate the properties of the bonded interface at room temperature. Shape memory and gecko adhesive schemes are eliminated by this requirement as present these typically evidence a glass or melt transition in this temperature range. It is additionally desirable that the reversible adhesive be depositable with a scalable process. A further requirement is that the resin be stable to the radiation conditions of the environment. 

ATSP's Self-Bond™ adhesive materials easily meet these requirements. Self-Bond resins are depositable with electrostatic powder deposition, meaning huge areas can rapidly be coated. Glass transition temperatures of the resin can reach 310°C and the resins feature intrinsically dynamically covalent bonds  which enables thermally-driven reversible bonding through a chemical mechanism call interchain transesterification (ITR). In recent work funded by NASA, we have demonstrated bonded components can have strengths of up to 60 MPa at room temp and the resin was able to demonstrate that the bondline could be broken and rejoined for >50 cycles with no degradation - demonstrating that the only limit of reversibility for ATSP's Self-Bond™ resins is ensuring that the adhesive does not delaminate from the subtrate. Self-Bond offers high strength structural adhesive properties through 400°C and can be bonded in timescales of less than one minute. Finally, Self-Bond has demonstrated resistance to and continued function versus 10 year simulated exposure to the atomic oxygen and proton radiation environments present in LEO.

These features combine to make Self-Bond™ ideally suited to space development as well as industrial applications here on Earth. Self-Bond products include formulated powder coatings for metals and advanced composites, film adhesives, glass-fiber reinforced film adhesives, toll coating, as well as consulting and joint development for your applications.


Self-Bond: A Unique Manufacturing Process