Preparation and Self-Healing Application of Isocyanate Prepolymer Microcapsules

Abstract

In this study, we successfully manufactured polyurethane microcapsules containing isocyanate prepolymer as a core material for self-healing protection coatings via interfacial polymerization of a commercial polyurethane curing agent (Bayer L-75) and 1,4-butanediol (BDO) as a chain extender in an emulsion solution. With an optical microscope (OM) and a scanning electron microscope (SEM), the resulting microcapsules showed a spherical shape and an ideal structure with a smooth surface. Fourier transform infrared spectra (FTIR) showed that the core material was successfully encapsulated. Thermal gravimetric analysis (TGA) showed that the initial evaporation temperature of the microcapsules was 270 °C. In addition, we examined the influence of the concentration of the emulsifier and chain extender on the structure and morphology of the microcapsules. The results indicate that the optimal parameters of the microcapsule are an emulsifier concentration of 7.5% and a chain extender concentration of 15.38%. Microcapsules were added to the epoxy resin coating to verify the coating’s self-healing performance by a surface scratch test, and the results showed that the cracks could heal in 24 h. Furthermore, the self-healing coating had excellent corrosion resistance.

Emulsion Stabilization Strategies for Tailored Isocyanate Microcapsules

“…However, GA is composed of arabinogalactan (88.4%), arabinogalactan protein (10.4%), and glycoprotein (1.24%), and its emulsifying property is mainly attributed to arabinogalactan protein, which is the reason for the high amounts needed to reach a stable emulsion [ 8 , 9 ]. Studies report on the optimization of the GA concentration targeting the control of the MCs’ morphology, size, and size distribution [ 10 , 11 , 12 ]. It was observed that as the GA concentration increases, the sphericity and uniformity of the MCs improve.…”

“…It was observed that as the GA concentration increases, the sphericity and uniformity of the MCs improve. However, it is only for concentrations of GA above 12 wt% that a significant reduction in the MCs size occurs, which is correlated with a considerable increase in the continuous phase viscosity [ 10 , 11 , 12 ]. Examples of other stabilizers reported in the literature for this application are Tween 80, Tween 20, Sodium dodecyl sulfate (SDS), SPAN20, polyvinyl alcohol (PVA), dodecyl benzene sulfonate (SDBS), and combinations of GA with CTAB (cetrimonium bromide) and PVA with SDS [ 11 , 12 , 13 , 14 ].…”

“…However, it is only for concentrations of GA above 12 wt% that a significant reduction in the MCs size occurs, which is correlated with a considerable increase in the continuous phase viscosity [ 10 , 11 , 12 ]. Examples of other stabilizers reported in the literature for this application are Tween 80, Tween 20, Sodium dodecyl sulfate (SDS), SPAN20, polyvinyl alcohol (PVA), dodecyl benzene sulfonate (SDBS), and combinations of GA with CTAB (cetrimonium bromide) and PVA with SDS [ 11 , 12 , 13 , 14 ]. As an alternative, microfluidic systems have also been used to produce MCs with homogeneous sizes; however, batch processes are better implemented in the industry and allow for a higher production output [ 15 , 16 , 17 ].…”

Self-healing materials for potential use in textile and clothing applications

“…In addition, a commercial polyurethane hardener (Bayer L-75) and 1,4-butanediol (BDO) as a chain extender in an emulsion solution were used for interfacial polymerization. It was found that addition of gum arabic (GA) reduced the adhesion phenomenon and improved microcapsule surface appearance by making them smoother [37]. Fig.…”

Development and characterization of self-healing microcapsules, and optimization of production parameters for microcapsule diameter and core content

“…, 2017), solvents (Tezel et al. , 2020) and self-healing materials (Xiang et al. , 2022; Santos et al.…”