Mineral fillers and functional additives for compounding u2014 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 toncut cost, add stiffness, or change appearance. In plastics they fall into two jobs:nextenders such as ground calcium carbonate that displace resin volume cheaply, and functionalnfillers such as fumed silica, titanium dioxide, and amorphous silica that modify a specificnproperty u2014 reinforcement, whiteness, rheology, or surface matting. Most filled compounds usenboth an extender and one functional grade.
nnCalcium carbonate is the volume workhorse: loadings of 20-40% by weight are routine in PVCnand polyolefins, and it lowers cost per part. The trade-off is mechanical u2014 high loading dropsnimpact strength and raises density unless the particle is surface-coated and the dose is balancednagainst the property target. Use a fine, coated grade where impact retention matters; use ancoarser uncoated grade where cost rules the formulation.
nnThe functional grades are dosed for an effect, not for volume. Fumed silica works at lownloadings, often 1-5%, as a thixotrope and reinforcing filler; titanium dioxide is the standardnwhite opacifier and also screens UV; amorphous silica serves as a matting and anti-blockingnagent in film. Specify the functional grade by the property you need, then let calcium carbonatencarry the cost-reduction load.
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