SYNOPSISTriboelectrification of small polymer particles ( < 10 microns) in which various functional groups are introduced by addition of substituted comonomers is studied. The particles are produced by suspension polymerization and mechanical crushing of larger particles. The effect of the different production methods on the particle is described. The particles produced by the polymerization method have a spherical shape with a smooth surface, and those produced by the crushing method have an irregular shape. Studies show that particles that have easily ionizable functional groups are charged more effectively. It is believed the iontransfer route is the dominant mechanism in the triboelectrification charging of the particle. The magnitude of charge becomes saturated after 0.5% addition of substituted comonomers in the particle. The particles produced by the polymerization method have a tendency to be charged effectively compared with those produced by the crushing method. I NTRO DUCT1 0 NThe triboelectrification of polymer particles is an important component for the process of electrophotography and for electrostatic paint application. Micron-sized polymer particles have attracted great interest from informational industries, especially in the field of the electrophotography. Triboelectrification is one of many very important properties for the toner particle. In spite of the importance of the triboelectrification property, only a few have reported the relationship between the sign and magnitude of the charge and the chemical structure of the particle material. A small number of reports do show limited qualitative rankings of various material~.'-~ We report triboelectrical charging data of micronsized polymer particles in which various chemical functional groups are introduced. The particles are produced by suspension polymerization and the me-