Self-Healing Coatings Containing Core–Shell Nanofibers with pH-Responsive Performance

Abstract

The micro−nanofibers prepared by the electrospinning technique can be used as a good container for loading healing agents. The core−shell electrospun nanofibers with polyacrylonitrile as the outer shell and tannic acid (TA) and tung oil as the core healing agents were synthesized by a coaxial electrospinning method and exhibited pH-sensitive ability. The nanofibers as additives were added to an epoxy resin coating as a self-healing coating. The morphological stability of the electrospun nanofibers were observed by a scanning electron microscope and a transmission electron microscope. Fourier transform infrared spectroscopy and fluorescence microscopy reveal that the successful synthesis and uniform distribution of core−shell fibers. The mechanical properties test revealed that the tensile properties of the coating could be improved by adding nanofibers. The infrared mapping test, energydispersive spectrometry, and X-ray photoelectron spectroscopy, which were carried out on the scratched part of the coating, proved the release of the healing agent in the damaged part. TA forms a protective film on the exposed metal surface through molecular adsorption under acidic conditions. Meanwhile, the curing of tung oil can effectively compensate into the microcracks to form a TA protective film, which could improve the self-healing performance. As the tung oil dries and solidifies in the alkaline solution, the cross-linking effect of the molecules is combined to form a tight film and strength the self-healing ability. TA as an acidic healing agent and tung oil as an alkaline healing agent played the role of pH-sensitive products in healing the cracked coating. The selfhealing rates of coating immersing in 3.5 wt % acidic NaCl solution and alkaline solution were 81.6 and 71.2%, respectively. The composite coating shows a great pH-sensitive self-healing ability to heal the cracked coating.

Main‐Side Chain Hydrogen Bonding‐Based Self‐Healable Polyurethane with Highly Stretchable, Excellent Mechanical Properties for Self‐Healing Acid–Base Resistant Coating

“…Most of the self‐healing coatings researched at present rely on local ultraviolet radiation or heating to complete the self‐healing. [ 48–51 ] Making rapid self‐healing coatings without external energy is still a challenge. Moreover, coating materials often face many complex environments, which require coating materials to have certain reliable mechanical properties.…”

Corrosion Performance and Rust Conversion Mechanism of Graphene Modified Epoxy Surface Tolerant Coating

“…In Figure 6, R s is the solution resistance, and R c and CPE -1 represent the coating resistance and coating capacitance, respectively. R ct and CPE -2 represent the charge-transfer resistance and double-layer capacitance, respectively (Wang et al, 2021;Cui et al, 2018). Figure 8A was used to fit the EIS data for PA/G/EP during the 96-h immersion, and Figure 8B was used to fit the EIS data which have two time constants (Pan et al, 2020).…”

pH-Responsive Electrospun Nanofibers and Their Applications

“…Due to their ability to be ionized in an aqueous environment, applications using polyelectrolytes can be found across many disciplines, such as in medicine, mineral separation, paints, food industry, corrosion inhibition, water purification and filtration, or cosmetics. [10,13,[22][23][24][25][26][27] In the past decades, the design of pH-responsive biomedical systems has been the focus of many research groups as for example shown by responsive lipid or polymeric nanoparticles using ionizable polymers. [28][29][30][31][32][33] This is attributable to the wide range of pH-differences found within the human body and the numerous pathological conditions inducing pH changes occuring for example in tumors, due to inflammation or during the wound healing process.…”