RHEOLOGICAL AND CRYOGENIC-TRANSMISSION ELECTRON-MICROSCOPY PROBING OFTHE STRUCTURE OF MAGNETIC PAINTS

Rheological measurements and cryogenic transmission electron microscop y are used to probe the structure of model magnetic paints which conta in ferrimagnetic pigment particles of barium ferrite, a wetting resin, and a solvent. As the resin concentration c increases, the storage mo dulus goes through a minimum. At low c, a flocculated network is devel oped in the paint. Milling of the paint at insufficient resin concentr ation does not improve its dispersion quality, but instead results in the formation of a stronger network. Milling at higher c effectively d isrupts the network into small aggregates. The resin concentration req uired to provide effective milling is lower for paints containing the larger iron oxide particles. (C) 1997 American Institute of Physics.