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Alginate microcapsules containing epoxy resin were developed through electrospraying method and embedded into epoxy matrix to produce a capsule-based self-healing composite system. These formaldehyde free alginate/epoxy microcapsules were characterized via light microscope, field emission scanning electron microscope, fourier transform infrared spectroscopy and thermogravimetric analysis. Results showed that epoxy resin was successfully encapsulated within alginate matrix to form porous (multi-core) microcapsules with pore size ranged from 5–100 μm. The microcapsules had an average size of 320 ± 20 μm with decomposition temperature at 220 °C. The loading capacity of these capsules was estimated to be 79%. Under in situ healing test, impact specimens showed healing efficiency as high as 86% and the ability to heal up to 3 times due to the multi-core capsule structure and the high impact energy test that triggered the released of epoxy especially in the second and third healings. TDCB specimens showed one-time healing only with the highest healing efficiency of 76%. The single healing event was attributed by the constant crack propagation rate of TDCB fracture test. For the first time, a cost effective, environmentally benign and sustainable capsule-based self-healing system with multiple healing capabilities and high healing performance was developed.

An epoxy (diglycidyl ether of bisphenol A) and a hardener (mercaptan/tertiary amine) were encapsulated within alginate biopolymer to form self-healing multicore microcapsules.

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Polyurea nanocomposites appear to be a recent advanced elastomer with high robustness. This study shows that without chemical surface functionalization, multiwalled carbon nanotubes (MWCNTs) can significantly increase the tensile strength of aliphatic polyurea nanocomposites which are cured at room temperature. This is achieved via ultrasonic dispersion techniques which prevent agglomeration and the role of MWCNTs as physical crosslink sites, encouraging the formation of hydrogen bonds, thus entangling the polymer chains in the polyurea matrix and restricting chain movement. The incorporation of MWCNT drastically increases the tensile strength of the nanocomposite by 1000%, from 2.16 ± 0.24 MPa to 21.7 ± 4.4 MPa. The thermal and chemical properties of samples are investigated using dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier‐transform infrared spectroscopy (FTIR), and acetone swelling tests. In this study, we showed that polyurea films reinforced with MWCNTs have high swelling resistance compared to the pure polyurea films. Aliphatic polyurea is also known to have high UV stability. The tensile properties achieved by the nanocomposite in this study are comparable to the aliphatic and aromatic polyurea products in the market and can make these films suitable products for rolling and coating applications.

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