Calcium carbonate (calcite crystal form) was dry-ground with a vibration mill consisted of an alumina vessel and balls. ESR spectra and X-ray diffraction patterns of the ground samples were measured. SEM photographs of the samples were also taken. The root-mean-squared strain and crystallite sizes of the samples were determined by Stokes-corrected Fourier analysis of the X-ray peaks. In the early stage of grinding, the amorphous calcium carbonate in the particles was deposited as aragonite crystalline on the surface of the calcite crystallite. And amorphous manganese, which was impurity for the amorphous calcium carbonate, was replaced by the position of Ca2+ of the aragonite as Mn2+. The aragonite was transformed to calcite in the middle stage of grin-ding. In further grinding, the amorphous calcium carbonate was deposited on the calcite crystallite surface as calcite. Then the position of Ca2+ of the calcite was replaced by Mn2+, and the ultrafine particles of the calcite crystallite were developed to be large mechanochemically calcined particles.
Ink transfer and splitting between roll nips were investigated from a viewpoint of rheology using simple disperese systems : low-consistency suspensions of carbon black in alkyd resinmineral oil vehicle. Rheological properties such as steady-shear viscosity and extensional viscosity were measured by several rheometers. The pressure profile in the ink film with the passage of time through a roll nip was determined using modified rolling cylinder tack meter. The absolute value of the minimum point in the pressure profile was correlated to tack value and the relations between the rheological properties of the suspensions and ink splitting behavior were mainly discussed. On the other hand, the growth and rapture of filaments between rollers were monitored by a monitoring system consisting of roller assembly with a pair of disk rollers and an image-analyzing video system. Followings are confirmed. The tack value depends on the shear stress at higher rates of shear but does not depend on the extensional viscosity. The relation between the filament length and extensional viscosity is not clear. The filament length does not depend on the characterisitcs of carbon blak but depends on the molecular weight of alkyd resin in the vehicle : The higher the molecular weight is, the longer the filament is.
Time dependent viscoelastic properties and stress overshoot of suspensions of brilliant carmine 6B in polybutadiene were investigated. Brilliant carmine 6B used in this study is a common magenta pigment and its particles have scaly shape. The disperse medium, fluid polybutadienes have relatively defined chemical structure and can be adjusted in their viscosity. We have dispersed 20wt% of the pigment to the medium by flushing method. The effects of viscosity of the disperse medium on the rheological properties of the disperse system are discussed in comparison with suspensions of carbon black. In a low viscosity medium, the suspension of brilliant carmine 6B forms a denser network structure than in a high viscosity medium. Furthermore, in the case of low viscosity, network formation is faster and the strain sensitive viscoelastic properties are more pronounced. From a comparison with the suspensions of carbon black, on stress overshoot measurements, it was deduced that the unit structures broken down of brilliant carmine 6B were finer and the recovered structures were more fragile than those of carbon black.