Electrically conductive self-healing polymer composite coatings

Abstract

The goal of the research described herein is the fabrication and assessment of electrically conductive partially-cured epoxy coatings which, upon cracking, autonomously restore barrier, mechanical and electrical properties via a microcapsule based healing mechanism. Upon cracking, microcapsules in the crack path release the 'healing' solvent ethyl phenyl acetate (EPA), which locally swells the matrix, promoting crack closure and enabling the diffusion and subsequent reaction of the residual hardener in the vicinity of the crack. Two different self-healing coatings and two controls based on an electrically conductive epoxy resin with approximately 20% carbon nanotubes (CNTs) were fabricated. Electrochemical impedance spectroscopy was employed to evaluate the potential of the CNT and non-CNT containing encapsulated systems to restore relatively large cracks and thus restore the barrier function. An in-situ electro-tensile test in a microscope revealed that electrical conductivity and mechanical properties were restored to 64% (± 23) and 81% (± 39) respectively, which correlated to crack closure. Under appropriate testing conditions the system showed successive damage-heal events in terms of electrical conductivity.

Protective Coatings Based on PMMA–Silica Nanocomposites Reinforced with Carbon Nanotubes

“…The observed improvement of corrosion protection efficiency of the brass in 3.5% NaCl solution relative to coatings without CNTs was explained by the authors in terms of an increase in electrical conductivity of the CNT-loaded coatings to help form anodically protecting passive oxide films on the metal and also to the increase in tortuosity of the paths corrosive ions have taken through the coating to reach the passive film in order to attack it chemically [15]. The ability for deliberately undercured coatings with 20 wt.% of CNTs and microcapsules containing electrically conductive epoxy resin with selfhealing property has also been demonstrated [16]. In this work, Bailey et al used a novel electrotensile test.…”

“…In this work, Bailey et al used a novel electrotensile test. Upon cracking of the undercured coating during tensile testing, microcapsules in the crack path release the healing solvent ethyl phenyl acetate (EPA), enabling the subsequent reaction with residual hardener in the vicinity of the crack to make the matrix swell locally and cause cracks to be closed [16].…”

Blood Pressure Sensors: Materials, Fabrication Methods, Performance Evaluations and Future Perspectives

“…CNTs are favorable in sensors due to their high electric conductivity and ease of functionalization [496,497]. Hence, it is perfect for self-healable sensing structures based on metal-ligand coordination [498], electrostatic interactions [499], hydrogen bond [500,501] In microcapsule-based self-healing mechanism [502], healing temperature [503] and CNT content [504] affect the thermal, electrical, and mechanical properties differently. When using G-CNT altogether, the G-CNT heterostructures may induce a synergistic effect that can improve its tensile strength and self-healing property [505].…”

Soft Self-Healing Nanocomposites

“…The design of materials having self-healing abilities requires a multidisciplinary process including mechanics, process dynamics, and chemistry. Several realistic strategies have been formulated over the past two decades (Chen et al, 2002;White et al, 2002;Gould, 2003), including elastomers (Sordo et al, 2015), coatings (Samadzadeh et al, 2010;Bailey et al, 2015;Zhang et al, 2018), and composite materials (Cho et al, 2009;Cohades et al, 2018), which not long ago appeared a creation of vivid imagination. A number of review articles comparing different healing concepts in bulk as well as composite materials is available (Caruso et al, 2009;Blaiszik et al, 2010;Binder, 2013;Herbst et al, 2013;Yang and Urban, 2013;Bekas et al, 2016;Cohades et al, 2018).…”