Overview
ISO 19246:2016 defines a standardized laboratory method to measure the oil absorption of precipitated silica used as rubber compounding ingredients. The standard specifies the determination of the DOA absorption number - the amount of di-(2-ethylhexyl) adipate (DOA) absorbed by silica - using an absorptometer equipped with torque measurement. The DOA absorption number indicates the void volume formed by silica aggregates and agglomerates and is used for quality control and material specification.
Key technical topics and requirements
- Scope and principle
- Measures liquid absorption capacity of pigments and extenders (precipitated silica) using DOA (CAS 103-23-1).
- Absorption determined by adding DOA to a kneaded silica sample while monitoring torque; the 70% value of the maximum torque from a smoothed polynomial curve is used to calculate the DOA absorption number.
- Materials & sample types
- Works for powder, micro-perls and granulated silica (granule fraction 1.0–3.15 mm).
- Moisture (loss on drying) must be considered; results can be reported on original or moisture-corrected (dry) basis.
- Equipment & parameters
- Absorptometer with burette and torque data processing; supplementary equipment includes sieves, balance (0.01 g), oven (105 °C) and cleaning tools.
- Typical measurement settings: DOA dosing rate 4.0 ml/min, target temperature 23 °C (±5 °C), specified rotation speeds and evaluation thresholds included in the standard.
- Procedure & evaluation
- Sampling per ISO 15528; carry out determinations in duplicate.
- Method A for powders/micro-perls (typical sample weight 12.50 g; adjustments recommended for tamped density extremes). Method B for granulated samples follows Method A after sieving.
- Evaluation uses a calculated polynom (third order) and reports DOA in ml/100 g. Moisture correction follows formulae in the standard.
- Quality controls
- Normalization of mixer chamber to account for abrasion/aging (Annex A) and precision data (Annex B).
- Test report must reference ISO 19246:2016 and include method, DOA absorption number, sample identity and any deviations.
Practical applications and users
- Used by rubber and tire manufacturers, silica producers, and quality control laboratories to:
- Specify and control silica properties for rubber compounding.
- Compare silica grades and monitor production consistency.
- Replace hazardous DBP/DOP oil absorption tests with a safer DOA-based method.
- Also relevant for R&D teams formulating rubber compounds and suppliers demonstrating compliance with material specifications.
Related standards and keywords
- Normative references: ISO 787-2 (loss on drying), ISO 787-11 (tamped volume/apparent density), ISO 15528 (sampling).
- SEO keywords: ISO 19246:2016, DOA absorption number, oil absorption of precipitated silica, absorptometer torque measurement, rubber compounding ingredients, di-(2-ethylhexyl) adipate, silica testing, pigment and extender absorption.
