Relation between the limiting viscosity number of urea-formaldehyde prepolymer and the blue electronic ink microcapsules

In order to optimize the polymerization conditions of urea-formaldehyde (UF) prepolymer, the orthogonal design method was used to study the effect of the polymerization conditions on the limiting viscosity number of prepolymer. The results indicate that the optimal conditions are: T = 75°C, t = 60 min, the mole rate of U/F = 1:1.75 and pH = 9.0. The limiting viscosity number of UF prepolymer prepared at the optimal conditions was above 1.5. UF prepolymer with different limiting viscosity numbers was used to prepare the blue electronic ink microcapsules containing an electrophoretic display liquid (surface modified phthalocyanine blue BGS dispersed in tetrachloroethylene (TCE)). It was founded that the mean diameter of capsules reduced, the mechanical intensity heightened and the surface roughness decreased with the increase of the limiting viscosity number. The blue display particles homodispersed inside the capsule can move reversibly under a 0.1 V/μm DC electric field.