Overview
ISO 9298:2017 - Rubber compounding ingredients - Zinc oxide - Test methods - specifies laboratory methods for evaluating zinc oxide used in the rubber industry. The standard applies to commercial zinc oxides (direct/American, indirect/French, precipitated, calcined) and to surface‑coated grades (fatty acids, oils, wetting agents). ISO 9298:2017 defines required tests, sampling reference, and reporting elements to ensure consistent quality control of zinc oxide raw materials.
Key topics and technical requirements
- Scope and sampling: Sampling for dry zinc oxide powders is referenced to ISO 1124.
- Mandatory test suite (Table 1):
- Matter volatile at 105 °C (ISO 787‑2)
- Water‑soluble matter (ISO 787‑8)
- Acidity/alkalinity of aqueous extract (ISO 787‑4)
- Residue on sieve (ISO 787‑7)
- Nitrogen‑adsorption surface area (NSA, ISO 18852) - reported in m2/g
- Zinc oxide content (Annex A) - EDTA titration procedure and standardization using high‑purity zinc
- Trace metals (Annex B) - determination of lead, cadmium, copper and manganese by atomic absorption spectroscopy (specified wavelengths)
- Acid‑insoluble matter (Annex C)
- Surface‑coated materials: Evaluation of coated zinc oxides is performed without prior calcination or extraction so that coatings remain intact for meaningful dispersion assessment.
- Classification and typical values: Annex D describes types used in rubber compounding and typical properties.
- Test report requirements: The standard lists required report items (reference to ISO 9298, sample ID, ZnO content, metal contents, water‑solubles, acidity/alkalinity, sieve residue, surface area, acid‑insoluble matter, test dates, deviations).
Practical applications and users
- Quality control labs in rubber and tire manufacturing: incoming inspection and batch release testing for zinc oxide raw materials.
- Raw material suppliers: product specification, certification, and production control for different ZnO grades (direct/indirect/precipitated).
- Materials testing laboratories: standardized methods for comparability of results and trace metal determination.
- Product development and compounding engineers: selecting ZnO grades based on surface area, coatings and purity to optimize dispersion, vulcanization and performance.
- Procurement and compliance teams: verify supplier claims, regulatory limits for heavy metals, and ensure consistent compounding ingredients.
Related standards
- ISO 1124 - Sampling for dry powders (carbon black shipment sampling procedures referenced)
- ISO 787 series - Test methods for pigments and extenders (volatile matter, acidity/alkalinity, water‑solubles, sieve residue)
- ISO 18852 - Determination of multipoint nitrogen surface area (NSA / STSA)
ISO 9298:2017 provides a clear, referenced framework for zinc oxide test methods in rubber compounding, enabling reproducible quality control, regulatory compliance and informed material selection.
