Preparation of Epoxy Modified Polysiloxane Microemulsions

Microemulsion samples of epoxy modified polysiloxane were prepared by hydrolytic polycondensation of active centres instead of free radical polymerization. The reactions and mechanisms of the preparation of microemulsions were elucidated and the microemulsions were characterized by Fourier transform infrared spectroscopy (FTIR), photon correlation spectroscopy (PCS), transmission electron microscopy (TEM) and UV-visible spectrophotometry techniques. The effects of the amount of catalyzer and epoxy modifier were systematically studied. The results of FTIR spectroscopy indicated that the epoxy group successfully grafted onto the polysiloxane molecules. The microemulsions showed stability when the amounts of catalyzer and epoxy modifier were low. The particle size decreased and the size distribution widened with the increase of the catalyzer concentration. A slight variation of the particle size occurred when the amount of modifier varied under 1.0 wt%, although the particle size rose rapidly from about 40 nm to 180 nm when the content of modifier was beyond 1.0 wt%. The increasing amount of epoxy modifier gave narrower molecular size distribution and the appearance of microemulsions changed from a transparent or a semi-transparent state to an opaque state.