Overview
ISO 4652:2020 - "Rubber compounding ingredients - Carbon black - Determination of specific surface area by nitrogen adsorption methods - Single-point procedures" specifies two automated single-point nitrogen adsorption methods for measuring the specific surface area of carbon black used in the rubber industry. It defines:
- Method A: automatic gas chromatography (carrier-gas method, TCD-based)
- Method B: automatic volumetric method
The standard explains apparatus, sample preparation, degassing, measurement procedures, calibration and result expression. It notes that results can differ between the two single-point methods and from the preferred multipoint BET method (ISO 18852). These single-point procedures are not applicable to porous carbon blacks.
Key topics and technical requirements
- Principles: Single-point measurement at relative pressure 0.3; assumes BET intercept ≈ 0 (simplified vs. multipoint BET).
- Method differentiation:
- Method A uses a helium–nitrogen (70:30 by volume) carrier gas and thermal conductivity detection after liquid-nitrogen cooling.
- Method B uses an automatic volumetric adsorption instrument.
- Degassing: Specific degassing procedures differ for Method A and Method B (e.g., heating at 300 °C ± 10 °C for Method A) and are critical to reproducible results.
- Calibration & correction:
- Use of standard reference blacks (SRB) is recommended to investigate and correct method-dependent bias.
- Optional correction using multipoint nitrogen surface area (ISO 18852) is described.
- Apparatus & safety: Dewar for liquid nitrogen, heating device, thermal conductivity detector, pressure regulators and an analytical balance; normal laboratory safety applies.
- Sample mass guidance: Recommended test portion masses vary with carbon black series (e.g., higher surface area grades use smaller masses) to optimize precision.
- Limitations: Single-point results are inherently lower than multipoint BET results and are not suited to porous carbon blacks.
Applications and users
ISO 4652:2020 is intended for:
- Quality control and process monitoring in carbon black production and rubber compounding
- Incoming inspection in rubber compound formulation and tire/rubber manufacturing
- Testing laboratories performing routine surface-area checks where faster throughput is required than multipoint BET
- R&D labs for comparative screening (after correlation with multipoint measurements)
Typical users: carbon black manufacturers, rubber compounders, contract testing labs, material scientists and QA/QC engineers.
Related standards
- ISO 18852 - Multipoint nitrogen adsorption (preferred, more accurate BET monolayer determination)
- ISO 9277 - BET/related calculations (referenced for BET plot concepts)
- ISO 4652 also includes informative Annexes on correction by multipoint methods and precision data.
Keywords: ISO 4652:2020, carbon black, specific surface area, nitrogen adsorption, single-point method, Method A, Method B, rubber industry, BET, ISO 18852.
Open preview (PDF)Rubber compounding ingredients — Carbon black — Determination of specific surface area by nitrogen adsorption methods — Single-point procedures