Diffusion and Reaction Phenomena in Solution‐Based Healing of Polymer Coatings Using the Diels–Alder Reaction

Abstract

The healing of a furan-functional epoxy coating using bismaleimide (BMI) solutions is demo nstrated. Corrosion studies of scratched coated carbon steel show that solution healing of damaged coatings inhibits corrosion. The healing relies on (i) the diffusion of solution components into the polymer, causing the system to swell, thus bringing crack surfaces into contact, and (ii) Diels-Alder adduct formation between furan moieties of the polymer network and the maleimide, resulting in covalent bonding across the crack interface. For the system investigated, crack healing is reaction-limited for small crack widths. The results provide a guideline for the design and implementation of self-healing systems based on BMI solution encapsulation.

Sunlight‐Activated Self‐Healing Polymer Coatings

“…The released healing chemistry then repairs the damage. In coatings, self‐healing has been achieved with micro‐ and nanocapsules containing core materials such as linseed oil, polydimethylsiloxanes (PDMSs), polyurethanes (PUs), or silyl esters . Scribe damage to the coating exposes the substrate, ruptures the capsules, and releases the healing material.…”

“…The ruptured microcapsules healed the damage with added heat. Diels–Alder reactions were used by Pratama et al through the encapsulation of multimaleimides dispersed in a solvent and incorporating the capsules into a furan‐functionalized epoxy . The solvent acts to disperse the active healing agent and aid in crack closure by swelling the epoxy.…”

“…In coatings, selfhealing has been achieved with micro-and nanocapsules containing core materials such as linseed oil, polydimethylsiloxanes (PDMSs), polyurethanes (PUs), or silyl esters. [11][12][13][14][15][16][17][18][19][20] Scribe damage to the coating exposes the substrate, ruptures the capsules, and releases the healing material. Behzadnasab et al showed that larger capsules can lead to better healing performance through visual inspection of the coatings.…”

Recyclable biobased materials based on Diels–Alder cycloaddition

“…In addition, a number of thermally reversible healing materials and biological materials have been constructed based on this DA reaction . Modified epoxy resin was chosen by some researchers to construct DA reversible materials . Currently, most studies put emphasis on modifying the common epoxy monomer diglycidyl ether of bisphenol A (DGEBA) or changing the synthesis path to achieve epoxy healing materials, but ignore the improvement of the internal structure of epoxy materials.…”

Novel Diels-Alder based self-healing epoxies for aerospace composites

“…One of the first reports by Aubert [8] dates back to 2003, and details the reaction of a diepoxy-compound formed via the Diels-Alder reaction between two epoxy containing furans and a bismaleimide that results in an epoxy functionalised Diels-Alder adduct that can react further with aliphatic diamines. Since this early work, Wudl et al [9,10] and Palmese et al [11,12] have studied thermo-reversible cross-linking systems for epoxy resins, however, practical considerations remain limited due to the use of solvents, encapsulated reagents (uncontrollable mixing) and long healing times. Alternative DielsAlder based self-healing materials [13,14] have largely consisted of elastomeric hydrogel formulations (ideally suited to coatings or soft robotics) that, although they have a high strain to failure ratio they do not exhibit the high strength and stiffness requirements of high performance thermoset epoxy materials.…”