Microencapsulation of epoxy resins: Optimization of synthesis conditions

Abstract

In this work, a series of microcapsules were prepared by in situ polymerization in oil-in-water emulsion with poly(urea-formaldehyde) as shell material and diglycidyl ether of bisphenol F as core substance. Different reaction parameters were analyzed: emulsification conditions (time, agitation method and rate), the viscosity of the core phase, stirring speed during synthesis, core/shell mass ratio and drying process. Morphology, chemical structure, mean size, size distribution and thermal properties of the resulting microcapsules were studied by Scanning Electron Microscopy (SEM) and Optical Microscopy (OM), Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC). Several spherical microcapsules with different sizes and distributions were obtained by the adjustment of reaction parameters. Lyophilized microcapsules resulted in free flowing powders, which remained stable under more than 1 year at ambient laboratory conditions. From preliminary testing results, it was demonstrated that microcapsules fabricated under optimized reaction conditions had a satisfactory size and shell structure and were strong enough to bear the manufacturing of an epoxy-based composite material. Thus, results obtained in this work show that these microcapsules are potential candidates for the development of self-healing composites.