PREPARATION OF POLYIMIDE MICROSPHERES IN NON-AQUEOUS INVERSE EMULSION

A method was presented to prepare polyimide microspheres in non-aqueous inverse emulsion. The non-aqueous inverse emulsion was compounded with N, N-dimethyl formamide/(pluronic-F127, dodecylbenzenesulf)/liquid paraffin, in which the poly (amic acid) was synthesized with monomers of pyromellitic dianhydride and 4, 4'-diaminodiphenyl ether. Then the polyimide particles were precipitated through the chemical imidization using the acetic anhydride/pyridine mixture as dehydrating agent. Ultimately, polyimide particles were completely imidized via thermal imidization. The stability of non-aqueous inverse emulsion were investigated, and the effects of solid content and thermal imidization temperature on the morphology of polyimide microspheres were also discussed. The properties of the product were characterized with FTIR, SEM and TG/DTG. The results showed that it was favorable to form the polyimide microspheres with higher solid content and better emulsion dispersity. The non-aqueous inverse emulsion was optimal when the volume ratio of N, N-dimethyl formamide to liquid paraffin was 1 : 4, the mass ratio of pluronic-F127 to dodecylbenzenesulf was 3 : 2, and the content of emulsifiers was 9 wt%. In addition, the polyimide particles were well dispersive, spherical and highly thermal stable with a narrow size distribution when the solid content was 20% and the thermal imidization temperature was less than 330 degrees C. The average particle diameter was about 10 mu m.