Design Strategy for Self-Healing Epoxy Coatings

Abstract

Self-healing strategies including intrinsic and extrinsic self-healing are commonly used for polymeric materials to restore their appearance and properties upon damage. Unlike intrinsic self-healing tactics where recovery is based on reversible chemical or physical bonds, extrinsic self-healing approaches rely on a secondary phase to acquire the self-healing functionality. Understanding the impacts of the secondary phase on both healing performance and matrix properties is important for rational system design. In this work, self-healing coating systems were prepared by blending a bio-based epoxy from diglycidyl ether of diphenolate esters (DGEDP) with thermoplastic polyurethane (TPU) prepolymers. Such systems exhibit polymerization induced phase separation morphology that controls coating mechanical and healing properties. Structure–property analysis indicates that the degree of phase separation is controlled by tuning the TPU prepolymer molecular weight. Increasing the TPU prepolymer molecular weight results in a highly phase separated morphology that is preferable for mechanical performances but undesirable for healing functionality. In this case, diffusion of TPU prepolymers during healing is restricted by the epoxy network rigidity and chain entanglement. Low molecular weight TPU prepolymers tend to phase mix with the epoxy matrix during curing, resulting in the formation of a flexible epoxy network that benefits TPU flow while decreasing Tg and mechanical properties. This work describes a rational strategy to develop self-healing coatings with controlled morphology to extend their functions and tailor their properties for specific applications.

The Versatility of Polymeric Materials as Self-Healing Agents for Various Types of Applications: A Review

“…However, this phase-separated feature can only improve the mechanical performance, but not the healing functionality, of the resultant coating. Nevertheless, this study advocates the rational to control the morphology of the blend system in order to develop an efficient self-healing coating with targeted property profiles [ 49 ].…”

The curing kinetics and properties of self-healing and thermally conductive polymeric composites based on ethylene vinyl acetate copolymer filled with nano alumina

“…Dynamic reversible covalent bonding is the ability to fracture and reconnect chain segments under a particular condition. [18][19][20][21][22][23][24][25] It holds out the possibility to solve the problems mentioned above. Such as Lou 26 et al accessed imine bonds into elastomers to prepare self-healing elastomers with high fracture stress (≈3 MPa), high fracture strain (≈600%), and high self-healing efficiency (≈95%).…”

Soft segment‐free functional polyurethane: A versatile candidate for heat‐healability, non‐dissociative mechanism, and high elongation adhesive materials

“…Flexible diamines, hyperbranched epoxy resin, nanomaterials, and gel polymer elastomers were tested for this purpose 26,27 . Low molecular weight TPU prepolymers resulted in the formation of flexible epoxy networks with self‐healing property 28 . However, these attempts were met with limited success.…”