Calcium Carbonate as Plastic Filler

A wide selection is possible in natural calcium carbonate, both uncoated and coated. Looking at the ratios, they are the most important fillers used in the plastics industry. Annual usage amount for Thermoplastics and Thermosets is 3.5 million tons. Consumption for elastomers is almost 2.5 million tons. The consumption of calcium carbonate filler in adhesives and pastes is 900,000 tons.

Calcium carbonate fillers are distinguished according to the following applications;

• High chemical purity to eliminate the negative effects of aging of polymers
• Its high whiteness and low refractive index thus help to reduce the consumption of expensive materials such as titanium dioxide with high abrasiveness of calcium carbonate, but it is also very suitable for the production of colored products.
• Low abrasiveness, contributing to less wear of machine parts such as extruder screws and rollers.

Furthermore, surface coated materials are particularly easy to disperse. Therefore, even when using very high filler quantities, polymers do not lose their superior processing properties. In thermoplastics, finely ground calcium carbonate increases hardness without significantly affecting impact strength. Stretching helps prevent shrinkage in thin-walled plastic materials.

Calcium carbonate is non-toxic, odorless, tasteless, and even better, it complies with plastic packaging food regulations. It is widely used throughout the world and is one of the most economical fillers for plastic applications.

Precipitated calcium carbonate (PCC) for plastic applications should have the following properties.

• Average grain size 0.07-2.0 micron
• Whiteness 95-96%
• Oil absorption value 35-40 g per 100 g powder
• Surface area 10-25 m²/g

Thin PCC materials with a d50 value of 0.07 micron are generally used with a stearic acid coated surface. The main uses for PCC fillers are PVC plastisols, such as automotive parts. Here, PCC mostly affects the angular structures of plastisols. It prevents the plastic from dripping. Other applications are sealants and rubber. Until a few years ago, PCC fillers were frequently used in the production of rigid PVC profiles. Today these have been replaced by natural calcium carbonate. Because the PCC formula used in this field has increased its costs significantly. The main reason for this was that natural calcium carbonate was available at much lower prices. In addition, the easier dispersion feature of natural calcium carbonate compared to PCC enabled the filling ratio in the polymer metric to be increased. It is not uncommon to encounter 2 or 3 times more use than the normal rate.