Cooperative self-healing performance of shape memory polyurethane and Alodine-containing microcapsules

Abstract

In this study, a method to prepare self-healing coatings by incorporating Alodine-containing microcapsules as fillers in Shape Memory Polyurethane (SMPU) was presented.

Triple-Action Self-Healing Protective Coatings Based on Shape Memory Polymers Containing Dual-Function Microspheres

“…For corrosion protection, the most common self-healing strategy is to embed corrosion inhibitors as active healing agents in the coating matrix. − These corrosion inhibitors can leach into the coating defect and immediately suppress the corrosion reactions that take place at the exposed metal substrate. In many cases, proper encapsulation of the inhibitor is beneficial to preserve its reactivity and to achieve its sustained and environmentally (pH-, Cl-, redox) responsive delivery within the coating defect. − The containers for encapsulating corrosion inhibitors can be inorganic nanoparticles made of layered double hydroxides, , halloysites, , and mesoporous SiO 2 , , or organic micro- or nanocapsules, such as polyelectrolyte microcapsules, , fibers, and hollow polymeric microspheres. , For inhibitor-based coatings, the healing effects result from corrosion inhibition rather than by intrinsic repair of the barrier properties of the coating. Therefore, the healing efficiency depends critically on the intrinsic performance, irreversibility, leaching capacity, and the amount of inhibitor in the coating.…”

Shape Memory Corrosion-Resistant Polymeric Materials

“…When damage occurs, the microcapsule breaks down, which allows for the healing agent to react with the metal substrate to form a passivating conversion layer; this provides time for healing to take place and prevents further corrosion. This basically means that healing is a two-step process in which the microcapsules disperse to form a passivating layer that improves the adhesion strength and corrosion resistance of the substrate, and from there, the matrix may then be heated to initiate the shape memory effect to close the damaged area [51]. Encapsulating a catalyst, where there exists an initiator pellet and a resin pellet, can act to induce self-healing in a polymer composite; this has been tested in polydimethylsiloxane successfully.…”

Shape Memory Polyurethane and its Composites for Various Applications

“…However, as the shape memory property is a physical phenomenon and does not involve any chemical bond brakeage and formation, it may not be fully possible to recover 100% of damage. Fan et al [59] have utilized microcapsules in bulk technique to produce SMP comprising self-healing ability called cooperative self-healing. They produced the microcapsules of a healing agent (Alodine 5200, mainly containing hexafluorotitanic acid (H 2 TiF 6 ) and hexafluorozirconic acid (H 2 ZrF 6 )) by coating a layer of polyurethane (toluene diisocyanate and 1,4-butanediol based polyurethane) over healing agent as core.…”

“…Schematic representation of cooperative self-healing: (a) Alodine microcapsules loaded polyurethane coating on aluminum alloy, (b) release of Alodine from the microcapsules caused by defect, (c) formation of Alodine conversion coating on aluminum alloy, (d) shape memory effect of polyurethanes stimulated by external heat, (e) completion of healing process of scratch[59].…”