Overview
EN ISO 3262-22:2023 - Extenders: Specifications and methods of test - Part 22: Flux‑calcined kieselguhr (ISO 3262-22:2023) specifies quality requirements and laboratory test methods for flux‑calcined diatomaceous earth (kieselguhr) used as an extender in coatings, rubber and other materials. The standard updates and replaces the 2001 edition, aligning product grades, analytical procedures and reporting requirements for consistent quality control across CEN/ISO member countries.
Key topics and technical requirements
The standard defines essential characteristics, required test methods and sampling/reporting rules. Principal topics include:
- Material definition: Flux‑calcined kieselguhr is a diatomaceous siliceous material calcined with a flux (e.g., soda ash or salt) at high temperature (~1 148 °C), producing a white, low‑iron glassy product.
- Essential requirements (examples of parameters specified):
- Silica (SiO2) content - minimum values specified (e.g., Grade A ≥ 85 % mass fraction; see Clause 6 for determination).
- Loss on ignition (LOI) - maximum specified.
- pH of aqueous suspension - specified range (7.0 to 10.5).
- Matter soluble in water and matter volatile at 105 °C - maximum limits.
- Residue on sieve / particle size indicators, specific surface area and oil absorption - grade‑dependent limits (oil absorption example: Grade A 120–200 g/100 g; Grade B 90–140 g/100 g).
- Test methods: References established ISO test methods (ISO 787 series, ISO 5794‑1, ISO 3262‑1). The silica determination procedure (Clause 6) uses controlled ignition, sulfuric and hydrofluoric acid digestion, duplicate determinations and muffle‑furnace ignitions with results reported to 0.1 %.
- Sampling & reporting: Sampling follows ISO 15528; test reports must identify product details, reference the standard, list results and methods, note deviations and anomalies, and include test dates.
Practical applications and users
This standard is directly useful for:
- Manufacturers of flux‑calcined kieselguhr for product specification, quality control and batch release.
- Coatings, ink and paint formulators who use kieselguhr as an extender for opacity, rheology and cost control.
- Rubber compounders and plastics processors that require controlled filler properties (surface area, oil absorption).
- Testing laboratories and QC teams ensuring compliance with purchaser or regulatory specifications.
- Procurement and compliance officers specifying supplier acceptance criteria.
Using EN ISO 3262-22:2023 ensures reproducible test results, consistent product grades and clearer supplier/customer communication for applications that rely on flux‑calcined diatomaceous earth.
Related standards