EVALUATION OF POLYURETHANE HAVING SO3NA GROUP AS MAGNETIC BINDER

Magnetic layers were formed by use of polyrethane having SO3Na group a s binder of magnetic particles. A packing degree and surface roughness of magnetic layer were investigated. When magnetic layers were soaked into silicone oil, the silicone oil could penetrate into every void p erfectly. The void volume Fraction could be estimated by measurement o f the weight increase of magnetic layer by soak into silicone oil. Con tinuous void was formed along with the network structure of magnetic p articles. The void in magnetic layer was still continuous after calend er treatment. The void fraction of magnetic layer was affected by the intensity of interaction between binder polymer and magnetic particles , and time of formation of flocculation during dry of magnetic paint. Time of the formation of flocculation depended on the steric stabiliza tion by adsorbed polymer, and determined surface roughness of magnetic layer. The increase of SO3Na content was effective to intensify the i nteraction between binder polymer and magnetic particles, but it furth ered the formation of flocculation structure if solvent of magnetic pa int was not suitable for binder polymer.