ISO 3262-5:2023

Overview

ISO 3262-5:2023 - Extenders: Specifications and methods of test - Part 5: Natural crystalline calcium carbonate specifies the requirements and test methods for natural crystalline calcium carbonate used as an extender/filler. Published by ISO (prepared by ISO/TC 256 in collaboration with CEN/TC 298), this second edition updates the scope, test methods and references for quality control of calcium carbonate derived from limestone and marble.

Key topics and technical requirements

• Product definition: Natural crystalline calcium carbonate (calcium carbonate from limestone and marble).
• Grades and purity: CaCO3 mass fraction minima for grades A–D: 99%, 98%, 95%, 90% (see Table 1).
• Essential quality limits:
  • Matter volatile at 105 °C: max 0.4% (ISO 787-2).
  • Loss on ignition: max 46% (ISO 3262-1).
  • Matter soluble in water: max 0.5% (ISO 787-3 or ISO 787-8; method to be agreed between parties).
  • pH of aqueous suspension: 8 to 10 (ISO 787-9).
  • Matter insoluble in hydrochloric acid (max % mass): Grade A 1%, B 2%, C 8% - test method described in Clause 6 (acid digestion, filtration on 0.8 µm membrane, drying at 105 ± 2 °C, gravimetric calculation).
• Conditional requirements: Residue on 45 µm sieve (ISO 787-7), particle size distribution by laser diffraction (ISO 8130-13), colour/lightness, and resistivity of aqueous extract (ISO 787-14) - to be agreed between supplier and purchaser.
• Sampling and reporting: Sampling per ISO 15528; test reports must identify product, reference ISO 3262-5:2023, list methods, results, deviations and test date.

Applications and who uses this standard

ISO 3262-5:2023 is intended for manufacturers, suppliers and quality laboratories that produce, test or procure natural crystalline calcium carbonate used as extenders/fillers in industries such as:

• Paints and coatings (pigment/extender quality control)
• Plastics and composites (filler specifications)
• Paper and board (brightness and particle size control)
• Adhesives, sealants and construction materials

Procurement teams, technical managers, formulation chemists and compliance officers use this standard to specify material acceptance criteria, ensure reproducible particle size and purity, and reduce formulation variability.

Related standards (normative references)

Relevant cross‑references include:

• ISO 3262-1 (general test methods for extenders)
• ISO 787 series (general test methods for pigments and extenders)
• ISO 8130-13 (particle size by laser diffraction)
• ISO 15528 (sampling)
• ISO 3696 (water for analytical use)
• ISO 18451-1 (terminology)

Keywords: ISO 3262-5:2023, natural crystalline calcium carbonate, extenders, calcium carbonate specifications, test methods, particle size distribution, matter insoluble in hydrochloric acid, quality control, pigments and fillers.