Mineral fillers and functional additives for compounding — ground calcium carbonate extender plus fumed silica, titanium dioxide, and amorphous silica for reinforcement, opacity, and rheology.
Mineral fillers are finely divided inorganic solids compounded into a polymer to cut cost, add stiffness, or change appearance. In plastics they fall into two jobs: extenders such as ground calcium carbonate that displace resin volume cheaply, and functional fillers such as fumed silica, titanium dioxide, and amorphous silica that modify a specific property — reinforcement, whiteness, rheology, or surface matting. Most filled compounds use both an extender and one functional grade.
Calcium carbonate is the volume workhorse: loadings of 20-40% by weight are routine in PVC and polyolefins, and it lowers cost per part. The trade-off is mechanical — high loading drops impact strength and raises density unless the particle is surface-coated and the dose is balanced against the property target. Use a fine, coated grade where impact retention matters; use a coarser uncoated grade where cost rules the formulation.
The functional grades are dosed for an effect, not for volume. Fumed silica works at low loadings, often 1-5%, as a thixotrope and reinforcing filler; titanium dioxide is the standard white opacifier and also screens UV; amorphous silica serves as a matting and anti-blocking agent in film. Specify the functional grade by the property you need, then let calcium carbonate carry the cost-reduction load.
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