Micronized calcium carbonate

Selecting the correct particle size is critical for performance. For plastic and PVC industries, a D50 of 1.0 to 2.5 microns is standard to improve impact strength and surface finish. In the paint and coatings sector, ultra-fine grades (under 2 microns) are preferred for better opacity and gloss control. For paper manufacturing, coarser grades are often used as fillers to improve brightness and ink absorption. Always request a Particle Size Distribution (PSD) report to ensure consistency.

B2B buyers must ensure the CaCO3 content is ≥98% for premium applications. High levels of impurities like Iron (Fe2O3 < 0.02%) or Magnesium can cause yellowing in plastics or paints. For food or pharmaceutical grades, compliance with FCC (Food Chemicals Codex) or USP standards is mandatory. Always verify the Whiteness index, which should ideally be above 95% for high-grade micronized powder.

Surface-treated micronized calcium carbonate is essential for polymer processing. The stearic acid coating (typically 0.8% to 1.2% by weight) improves hydrophobicity and dispersion within the plastic matrix, reducing machine wear and increasing production speed. Untreated powder is more economical and suitable for water-based paints, rubber, and construction adhesives where oil-absorption properties are prioritized.

Inquire whether the supplier uses wet grinding or dry grinding technology. Wet grinding typically produces a narrower particle size distribution and finer particles, ideal for high-gloss coatings. Ensure the supplier utilizes automated air classifiers to guarantee the absence of oversized particles, which can cause streaks in thin-film extrusion or clogging in spray nozzles.

Micronized powder is highly susceptible to moisture absorption and contamination. Ensure the supplier uses multi-layer moisture-proof bags (PP/PE) or Jumbo bags with inner liners. For sea freight, specify the use of pallets with shrink-wrap to prevent bag breakage during transit. On Made-in-China.com, you can find 'Audited Suppliers' who provide specialized loading photos to verify container cleanliness.

Utilize Secure Payment services to hold funds until the shipping documents are verified. It is highly recommended to appoint a third-party inspection agency (like SGS or Intertek) to perform a Pre-Shipment Inspection (PSI). This inspection should focus on whiteness, particle size, and moisture content to ensure the batch matches the approved sample.

Prices for micronized calcium carbonate are sensitive to energy costs (grinding power) and raw stone quarry prices. Negotiate based on annual volume contracts rather than spot buys to lock in stable pricing. Ask for FOB (Free On Board) pricing to maintain control over your own shipping costs, as mineral freight rates can fluctuate significantly.

Ensure the HS Code (typically 283650) is correctly declared to avoid customs delays. Request a Certificate of Analysis (COA) for every batch and a Material Safety Data Sheet (MSDS) in English. For certain regions, check if there are anti-dumping duties or specific environmental import permits required for mineral fillers.