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GCC Specification

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

Property

Normal range

Comments

Calcium carbonate content%

90-98

Best products are >96%. Main impurity is magnesium carbonate

Color brightness (e.g., ISO R 457) Yellowness

  • 70-95
  • 1.4-7.0

Importance varies according to application Good color usually attracts a premium

Particle size Average (D50, microns) Top cut (D98, microns)

0.5-10.0

<10-100

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)

<1-10

Oil absorption (ml/100 g)

15-25

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

  • 400-900
  • 800-1,700

Table 2 Estimated use of GCC fillers by the various polymer types and application (world basis)

Polymer type

% of total tonnage

Comments

Thermosets

20

Mainly used in uncoated form Unsaturated polyester resin formulations (Sheet molding and bulk molding compounds)

Elastomers

20

Widespread use, especially in carpet backing Mixture of coated and uncoated

Thermoplastics

60

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.

 
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