Ground Calcium Carbonate (Fine, d50 5µm)

Fine ground calcium carbonate with a median particle size of 5 µm offers an improved balance between cost-effective volume extension and enhanced mechanical performance compared to coarser grades. The finer particle size increases surface area to approximately 3–5 m²/g, promoting better resin wetting and dispersion throughout the matrix.

This grade is particularly well-suited for gelcoat formulations, surface-quality-sensitive RTM parts, and applications where a smooth, defect-free surface is required. The finer particles contribute to improved flexural strength and impact resistance compared to coarse grades, while still providing significant cost savings versus pure resin systems.

Fine GCC is compatible with all major thermoset resin systems and cure packages. It is used at typical loadings of 30–100 phr in UPR systems and 20–60 phr in epoxy systems. When combined with thixotropic agents such as fumed silica, fine GCC-filled formulations can be applied vertically without sagging. The material is available in both untreated and stearic acid-coated versions, with the coated variant providing improved dispersibility and slightly lower moisture sensitivity.