The main properties, with usual ranges given for commercial grades of GCC, are presented in Table 1.
Polymer Applications of GCCs
GCC is an ideal, low cost, and easily used filler for many polymer applications. The low cost makes it possible to reduce raw material costs by replacing polymer by GCC, although the savings are not as great as it appears possible on first sight, as the higher specific gravity means that 2.5-3 times as much weight of filler is needed to replace polymer on a volumetric basis, and additional cost is often incurred to incorporate and efficiently disperse the particulate GCC.
Table 1 The main properties usually given for GCC fillers and the normal ranges encountered
Calcium carbonate content%
Best products are >96%. Main impurity is magnesium carbonate
Color brightness (e.g., ISO R 457) Yellowness
Importance varies according to application Good color usually attracts a premium
Particle size Average (D50, microns) Top cut (D98, microns)
The two values give an indication of the width of the particle-size distribution. Premium products are at the bottom end of the size range and the lower end of the “top- cut” range. Some applications require a narrow distribution, while others require special distributions to maximize packing
Specific surface area (BET, m 2.g -1)
Oil absorption (ml/100 g)
This is an important indication of how much of the filler can be incorporated into the polymer. The lower the oil absorption, the higher the obtainable loading, which is important where the filler is being used for pure cost reduction
Powder density (aerated) kg.m~3 (tapped) kg.m~3
Table 2 Estimated use of GCC fillers by the various polymer types and application (world basis)
% of total tonnage
Mainly used in uncoated form Unsaturated polyester resin formulations (Sheet molding and bulk molding compounds)
Widespread use, especially in carpet backing Mixture of coated and uncoated
Flexible PVC is the largest market (especially cable insulation and flooring). Significant use also in rigid PVC (pipes and extrusions), polypropylene (garden furniture, household appliances, and automotive), and polyethylene (microporous film and cables). Again, both coated and uncoated forms are used
The world market for GCCs in polymer applications is over ten million tonnes, and Table 2 gives the estimated breakdown by polymer type and application.
The more important applications of GCC in the different polymer types are outlined below.