Surface chemistry and dispersion of magnetic pigment for a solventless process

Coupling agents with a variable spacer length between the silane and the branch point were synthesized. The chemical bonding between the silane group and the particle surface was confirmed by the Si 2s and Si 2p peaks in the X-ray photoelectron spectra. The surface coverage of the branched coupling agent with long spacer was larger than the branch with short spacer. A solventless formulation could be prepared up to 30 volume percent of the particle using the treated particles. The viscosity was shear rate dependent, showing a power law dependence for all formulations.