Overview
ISO 5796:2000 - "Rubber compounding ingredients - Natural calcium carbonate - Test methods" specifies standardized laboratory test methods for evaluating natural calcium carbonate (chalk or limestone) ground to a dry powder for use as a filler/extender in the rubber industry. The standard covers sampling, a range of physical and chemical tests used for quality control, and includes normative atomic absorption procedures for metal determinations. It explicitly excludes calcium carbonates produced by precipitation (precipitated calcium carbonate).
Key topics and requirements
- Scope and sampling
- Applies to natural calcium carbonate powders intended for rubber compounding.
- Sampling is to be performed in accordance with ISO 15528.
- Primary test methods
- Particle-size / residue on sieves (using 45 µm and 125 µm test sieves per ISO 565).
- Calcium carbonate content (on a dry sample) and loss on heating at 105 °C (ISO 787-2).
- Loss on ignition at 1 000 °C, measured on a dry sample.
- Matter insoluble in hydrochloric acid - procedure, filtration and gravimetric expression.
- Alkalinity - titrimetric determination expressed as g Na2CO3/100 g sample.
- Trace metal analysis
- Two approaches are provided:
- Traditional spectrophotometric methods (in the main body for copper, manganese, iron). These methods are noted as obsolescent and use chlorinated solvents.
- Atomic absorption methods (normative Annexes A, B and C) are recommended as replacements for the spectrophotometric procedures for determination of total copper, manganese and iron.
- Annex D (informative) provides classification guidelines by fineness and typical physical/chemical properties relevant to rubber compounding.
- Safety note: normal laboratory safety practices apply; strong acids and high-temperature steps are used.
Applications and who uses it
ISO 5796:2000 is primarily used for:
- Quality control (QC) of natural calcium carbonate used as fillers in tire, hose, sealant and general rubber compound production.
- Incoming inspection by rubber manufacturers and raw-material suppliers to verify fineness, purity and contaminant levels.
- Analytical and contract testing laboratories performing standardized tests for customers and compliance reporting.
- R&D and formulation teams needing reliable material characterization to optimize dispersion, mechanical properties and processing behaviour.
- Procurement and specification development, enabling consistent supplier acceptance criteria.
Keywords: ISO 5796:2000, natural calcium carbonate, rubber compounding, test methods, calcium carbonate testing, fillers, atomic absorption, spectrophotometric methods, sieve residue, loss on ignition, matter insoluble in HCl, alkalinity, quality control.
Related standards
- ISO 15528 (sampling)
- ISO 565 (test sieves)
- ISO 787-2 (loss on heating)
- ISO 3262-1 (extender test methods)
These referenced standards support specific test procedures and apparatus requirements cited in ISO 5796:2000.
