Thermally-Induced Self-Healing Behaviors and Properties of Four Epoxy Coatings with Different Network Architectures

Abstract

Abstract:The thermally-induced self-healing behavior of polymer coatings consists of two steps, i.e., gap closure and crack repair. In addition, the polymer coatings with thermally-induced self-healing capability are expected to show satisfied properties to ensure the application. Here, four epoxy coatings with dense irreversible Network I, dense reversible Network II based on a Diels-Alder (DA) reaction, loose irreversible Network III, as well as partially irreversible and partially reversible Network IV were prepared, respectively. The dense irreversible Network I showed an evident gap closure upon heating, while the crack still existed at the high temperature. The dense reversible Network II presented good self-healing upon direct heating at a high temperature of 150 • C, leading to the quick gap closure in 40 s and subsequent crack disappearance in 80 s. The loose irreversible Network III showed negligible crack variations upon heating, while the partially reversible and partially irreversible Network IV showed quick gap closure as well but only partial crack disappearance. Besides, the coating with the reversible Network II based on the DA reaction not only presented good self-healing capability but also possessed the satisfied mechanical properties and the best electrochemical corrosion property, ensuring its further exploitation and potential practical applications.

One-Pot Synthesis and Characterization of Novel Shape-Memory Poly(ε-Caprolactone) Based Polyurethane-Epoxy Co-networks with Diels–Alder Couplings

“…The latter was obtained by the reaction of isocyanate functionalized prepolymer with FA (see Figure 2). To link the FA-end-functionalized prepolymers to the FA_DGEBA oligomer, BMI was added to the reaction mixture, which led to formation of the DA-adducts (see EP-PU [16][17][18][19][20][21][22][23][24]. It is noteworthy that only selected EP-PU samples were subjected to some investigations to keep this contribution in limits.…”

“…The first synthetic way for the preparation of samples EP-PU 1-15 was the incorporation of a HO-ended DA adduct in the networks composed of isocyanate (HDI) terminated polyurethane prepolymer and DGEBA and followed by crosslinking of the EP-component by polyetheramine (Jeffamine ® EDR 176). The other synthetic route utilized the reaction between furanyl end-functionalized PU polymers and FA_DGEBA oligomer in the presence of BMI as the coupling agent (samples EP-PU [16][17][18][19][20][21][22][23][24]. Thus, the two synthetic routes differed from one another in generation of the DA-adducts and in the composition of the co-networks.…”

“…Table 4. Although the mechanical properties of the EP-PU systems prepared by the second synthetic approach (i.e., containing polymerized EP resin and DA adducts) do not show clear trends, some important conclusions can be drawn from the data in Table 5: (i) at low EP resin content, the increasing amount of the DA coupling agent considerably reduced the elongation at break (see samples EP-PU 16 and EP-PU 17); (ii) increase in the amount of EP resin in the samples prepared with PCL of M n = 10 kg/mol resulted in higher E-moduli (see samples EP-PU [16][17][18][19][20], while an opposite trend can be observed for the samples with PCL of M n = 50 kg/mol (see samples EP-PU 21 to 24); (iii) the elongation at break decreased with increasing EP content and with the M n of PCL; and (iv) the E-moduli are higher and the elongations at break values for the EP-PUs prepared by the second synthetic route (Scheme 2) are lower than those prepared by the first one (Scheme 1).…”

Near-Infrared Light and Solar Light Activated Self-Healing Epoxy Coating having Enhanced Properties Using MXene Flakes as Multifunctional Fillers

“…Further increasing MXene content to 5.44 wt % deteriorated the anti-corrosion capability. To further quantify the electrochemical corrosion properties, polarization resistance ( R p ) was calculated using the Stern-Geary equation [30], Rp=βaβc2.303(βa+βc)Icorr where, β a and β c are the anodic and cathodic Tafel constants. The calculated R p is listed in Table 2 as well.…”

Sorbitol as a Chain Extender of Polyurethane Prepolymers to Prepare Self-Healable and Robust Polyhydroxyurethane Elastomers

“…Its versatility has sparked great interest in self-healable PUs with higher durability when compared to the standard PUs. Moreover, self-healable materials are eco-friendly and cost-effective [ 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 ].…”