Synthesis and characterization of self-healing silica microspheres doped with epoxy resin and methyl-ethyl-ketone catalyst by a modified Stöber method

Abstract Silica microspheres doped with epoxy resin and methyl-ethyl-ketone (MEK) catalyst were synthesized using a modified Stöber method. The resulting material is a potential candidate as self-healing additive for cementing slurries, especially for oilwell applications. Once dispersed in a cementitious matrix, the microspheres with encapsulated material rupture under the stress caused by cracks or damage formed in the cement sheath, bringing the epoxy resin in contact with the catalyst. The resulting polymerization reaction slows down the growth of the crack. The encapsulation process was carried out using a variation of the Stöber method to obtain micro/nano silica spheres. The resulting material was characterized by Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis, energy dispersive spectroscopy (EDS), scanning electronic microscopy (SEM) and BET surface area analysis. The results of the FTIR and thermogravimetric analysis confirm the presence of silica and the full encapsulation of resin and catalyst. SEM - EDS showed that the average size of the synthesized spheres is the range from 50 µm − 250 µm. BET analysis showed a superficial area of 46.785 m²/g and a pore volume of 0.0983 cm³/g for the doped silica microcapsules with epoxy resin. For the doped microcapsules with MEK, the surface area was 397.349 m²/g and the pore volume was 0.0280 cm³/g. SEM images showed that once added to a cement slurry, the synthesized capsules ruptured in the presence of cracks, releasing the reagents. The results showed that the synthesis process was successful for both encapsulated resin and catalyst.