Double-layered reactive microcapsules with excellent thermal and non-polar solvent resistance for self-healing coatings

Abstract

Double-layered polyurea microcapsules containing hexamethylene diisocyanate (HDI) with outstanding shell tightness have been successfully synthesized via interfacial polymerization reaction in an oil-inwater emulsion. The resultant capsules were systematically characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy. The reaction parameters including reaction temperature (40 C, 50 C, 60 C), reaction duration (1 h, 1.5 h, 2 h and 2.5 h), amount of Suprasec 2644 (2.4 g, 3 g and 3.6 g) and emulsification time (15 min, 45 min and 75 min) were investigated and evaluated in terms of core fraction and quality of microcapsules. The core fraction of microcapsules was reduced with an increase of reaction temperature, reaction duration, mass of Suprasec 2644 and emulsification time, while the quality of microcapsules fluctuated. The thermal and organic solvent resistances were assessed by using TGA and titration. The results showed that the microcapsules had 1.6% weight loss compared with pure HDI with 90% weight loss after 60 min isothermal treatment at 100 C. After immersion in various solvents for 24 days, the microcapsules released as low as $3% of core in weakly polar solvents (i.e. hexane and xylene), about 5-60% in polar aprotic solvents (i.e. ethyl acetate, acetone, DMF and DMSO), and 60-90% in water and polar protic solvents (i.e. isopropanol and ethylene glycol). Both fresh and hexane-treated HDI capsules showed excellent anticorrosion performance in scratched coatings via self-healing functionality, indicating promising practical application in industrial coating and paint systems.

Multilayer composite microcapsules synthesized by Pickering emulsion templates and their application in self-healing coating

“…Meanwhile, by applying this technology into coating industry, capsule-based self-healing materials open up a prosperous field of smart coatings that can give instant feedback to external signal, renovate themselves autonomously and significantly prolong the service life. 17 Therefore, selfhealing microcapsule is demanded to possess several features, which contain high encapsulation efficiency, well protective capability for core material and rapid responsiveness towards ambient hazards and so on, since it plays an important role in repairing performance of capsule-based intelligent materials. Upon crack damage of the self-healing coating, the embedded microcapsules simultaneously rupture, release the encapsulated healing reagents, and refill the cracked area.…”

Controllable Enhancement of Capsule‐Membrane Wrinkles by Flow Shear and Preparation of Double‐Layer Polyamide Microcapsules

“…The wrinkles are very important for the formation of MDPMs because they provide more space for water. Compared to single‐layer microcapsules, the MDPMs have many advantages and will become a new area of research …”

‘Containers’ for self-healing epoxy composites and coating: Trends and advances

“…Hence solvent and thermal resistant microcapsule are practically required for self-healing epoxy coatings. A novel doublelayered polyurea microcapsules containing hexamethylene diisocyanate (HDI) with excellent shell tightness synthesized via interfacial polymerization reaction showed good resistance to temperature and nonpolar solvents [55]. These HDI encapsulated double-layered polyurea microcapsules showed outstanding anticorrosion performance through selfhealing functionality of the released HDI in damaged locations.…”