Self-Healing Mechanism of Epoxy Resin Improved by Polydopamine Nanoparticles

Graphical The active groups on the PDA surface interact with the polymer network via reversible hydrogen bonds, imparting self-healing capabilities to the PDA/EP composite. When microcracks emerge, active groups at the fracture interface realign, and “adhesion” is restored through hydrogen bond reformation. Self-healing is achieved through the cleavage and reformation of hydrogen bonds. Thermosetting resins, due to their polymer structure, are easily damaged by mechanical, chemical, thermal, ultraviolet radiation and other factors, inevitably leading to local damage and microcracks difficult to detect, which impair mechanical properties and durability. To improve and test the self-healing properties of epoxy thermosetting resin, a protective coating with self-healing performance, polydopamine (PDA) self-healing modified epoxy resin (EP) composite material, was designed. The self-healing behavior and mechanism were tested and analyzed through tensile properties and digital speckle technology. Nano-PDA particles, synthesized via self-polymerization at pH = 9, exhibited uniform morphology and were incorporated into EP. Tensile performance experiments and digital speckle analysis were carried out on three types of composite materials, namely, PDA/EP, PDA/EP pre-damaged once, and PDA/EP pre-damaged three times. Therefore, 0.5wt%, 1.0wt%, and 1.5wt% PDA/EP composites exhibit varying degrees of reversible self-healing. When the PDA content is 1.0wt%, the strength recovery rate of the composite material reaches 87.1% after one pre damage and still reaches 83.9% after three pre damages. The strain cloud maps in the X and Y directions also indicate that PDA/EP materials can recover the structural stability at a certain degree after being per-damaged once or three times.