Preparation of monodisperse melamine-formaldehyde microspheres via dispersed polycondensation

We have successfully synthesized relatively monodisperse and cross-linked melamine-formaldehyde (MF) microspheres by dispersed polycondensation and subsequent pH adjustment with serum replacement cleaning. The average particle sizes ((D) over bar (w): weight-average and (D) over bar (n) : number-average), the polydispersity index ((D) over bar (w)/(D) over barn) the number of particles N-p, and the gel content of the M-F microspheres were observed by varying the pH, the surfactant concentration, and the polymerization temperature. We observed that both the pH and the polymerization temperature were predominant factors in determining (D) over bar (n) and Np, but the effect that the temperature and pH had on the gel content ( > 94% for all samples) was negligible. The exponents of the slopes of plots of N-p versus pH and surfactant concentration were -10 and 0.6, respectively. Particle nucleation and growth were achieved within short periods; the incessant coagulation occurred even in the presence of surfactants.