Morphologies of microparticles of partially neutralized sodium polyacrylate by inverse suspension polymerization

The morphologies of sodium polyacrylate super absorbent polymer microparticles synthesized by inverse suspension polymerization at 65 degrees C are presented. The spherical polymer microparticles of 30-100 m in diameter were prepared in a hydrocarbon medium with water soluble initiators in presence of a cross-linking agent and suspension stabilizer in a stirred batch reactor. A variety of microparticles morphology has been observed for different reaction conditions such as monomer/water ratio, reaction time, cross-linker type and concentration, hydrocarbon medium properties, and postreaction solvent washing. The observed polymer particle morphologies include highly deformed particles, spherical particles with smooth surfaces, spherical particles with wrinkled surfaces, particles with interior multihollows, highly porous particles, particles of empty core-shell structures, etc. Some of these particles with complex morphologies such as multihollow or porous interior can improve the water absorption efficiency of the polymer particles because water can penetrate the particle more effectively. The polymer particles with wrinkled particle surface, which is formed during the postreaction treatment process, can also enhance the water absorption rate because of its increased external surface area. POLYM. ENG. SCI., 58:1564-1574, 2018. (c) 2017 Society of Plastics Engineers