Mineral filled composites, fracture

IWATSUKI, T. Yoshida, H. 1999. Ground-water chemistry and fracture mineralogy in the basement granitic rock in the Tono uranium mine area, Gifu Prefecture, Japan - Groundwater composition. Eh evolution analysis by fracture filling minerals. Geochemical Journal, 33, 19-32. 

Rocks in most cases are heterogeneous composites only monomineralic rocks like rock salt or anhydrite contain only one mineral type. Heterogeneity becomes more contrasted if pores and fractures, filled with fluids, are present. Mineral composition, porosity/fracturing, and internal rock structure therefore influence the physical rock properties (Fig. 1.8). 

With respect to mechanical properties, the effect of any mineral filler is firstly related to particle size and particle size distribution. For instance, the impact resistance of a PP-talc composite strongly depends on those two filler characteristics, and it is easily understood that particles with excessive dimensions are likely to be fracture initiation sites. For mineral fillers which are extracted from lodes, grinding and sorting are thus key preparation steps, with obviously processing costs that dramatically increase as the targeted (average) particle size decreases. The balance between the benefits in mechanical or physical properties and the extra-cost of filler addition is therefore the bottleneck of all applications for filled thermoplastics. 

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