Electrically conductive self-healing polymer composite coatings
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. (C) 2015 Elsevier B.V. All rights reserved.