Monodisperse sulfonated melamine formaldehyde resin microspheres: Synthesis by dispersion polymerization and light-diffusing performance characterization

The development and characterization of sulfonated melamine formaldehyde resin microspheres (SMF microspheres) as light diffusers in epoxy resin was presented in this paper. The SMF microspheres were prepared through dispersion polymerization with uniform particle size, smooth surface, and a high refractive index. The particle size of the microspheres was controllable within the range from 0.8 to 3.7 µm according to the pH during acidic condensation and the amount of melamine. Compared to traditional MF microspheres, SMF microspheres possessed unique sulfonic acid groups, higher primary amine content, and stronger polarity, which prevent agglomeration when mixed with epoxy resin. The SMF microspheres thus prepared were used as light-diffusing fillers with epoxy resin as matrix. Experimental results and single-particle Mie scattering simulations confirmed that SMF microspheres with a higher refractive index and smaller particle size exhibited higher light-shading efficiency and the haze of EP, demonstrating their outstanding light-diffusing performance. In summary, the significant potential application of SMF microspheres in the field of light diffusers was demonstrated.