Optimized synthesis of isocyanate microcapsules for self-healing application in epoxy composites

Abstract

Microcapsules containing isophorone diisocyanate were fabricated in oil-in-water emulsion. The emulsification effect of different emulsifiers during the capsule synthesis was systematically investigated by optical microscope. Three kinds of shell materials were discussed to obtain the high core content, smooth-surfaced, and robust capsule by scanning electronic microscope and Fourier transform infrared spectroscopy. Self-healing performance of corresponding self-healing epoxy composites was fully evaluated by accelerated corrosion test and mechanical test. The results demonstrated that high core content and smooth-surfaced capsules with dense composite shell could be synthesized in polyvinyl alcohol emulsion, and the core content of the optimized capsules was determined as 71.3–84.6 wt% at the capsule size from 35 µm to 154 µm. In addition, the optimized capsules had good processing properties and the corresponding self-healing epoxy composites exhibited excellent core release and self-healing performance.

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 ].…”

A review on the self‐healing ability of epoxy polymers

“…In 1999, Zako et al 46 added small thermoplastic particles to thermosetting materials (glass fiber/epoxy composites), which melted upon heating, thus repairing the damaged cracks. They also confirmed that the addition of F I G U R E 5 A general mechanism to a typical ROMP reaction 35 Isophorone diisocyanate -polymerization reaction 86% 43 small thermoplastic particles did not reduce the strength of the thermosetting glass fiber composite. This technology enables the use of up to 40% thermoplastic adhesives in glass fiber reinforced epoxy composites.…”

A sandwich panel that autonomously repairs sudden large holes and defects for tankers and pipelines carrying hazardous matter

“…15 The most preferred method is to use microcapsules as containers for the healing agent and activator. Amine, 16 polydimethylsiloxane, 17 isophorone diisocyanate, 18 epoxy, 16,19 sodium monofluorophosphate 14 and PU resin [20][21][22][23][24][25] are among the materials used. Self-healing microcapsules are incorporated into the materials to repair damage or a crack.…”