Overview
ASTM D7772-15(2023) describes a standardized test method for determining the extractable content in carbon black by measuring the absorbance of a cyclohexane extract at 386 nm using a UV spectrophotometer. This test is essential for screening carbon black materials intended for use in products that will come into contact with food, ensuring compliance with regulatory requirements regarding purity and safety.
The procedure provides a reliable means of identifying extractable organic impurities in carbon black, helping manufacturers demonstrate that their products meet stringent global standards for materials in food contact applications.
Key Topics
- Test Principle: The method involves extracting a carbon black sample with cyclohexane, followed by absorbance measurement of the filtrate at 386 nm in a 50 mm cuvette. A value of less than 0.10 absorbance units typically indicates compliance with food contact standards.
- Screening Purpose: The procedure acts as a rapid and effective screening method for determining whether the carbon black falls within acceptable extractable limits for regulatory clearance.
- Required Equipment:
- UV spectrophotometer capable of 386 nm measurement
- Cuvettes with 50 mm optical path
- Analytical balance (0.01 g sensitivity)
- Filter paper, volumetric flasks, glass funnels, and other standard laboratory tools
- Calibration and Standardization: Regular calibration of the spectrophotometer is crucial, including using neutral density filters, to ensure accuracy and reproducibility of absorbance readings.
- Precision and Repeatability: Inter-laboratory studies have established repeatability (r) at 0.013 absorbance units and reproducibility (R) at 0.024 absorbance units, supporting the reliability of the method.
Applications
ASTM D7772-15(2023) is widely used in industries where carbon black could come into contact with food or sensitive applications requiring low extractable impurities:
- Food Contact Materials: Carbon black used in plastic, rubber, and packaging materials that must comply with national and international food safety regulations.
- Material Qualification: Screening raw materials for compliance before further processing or inclusion in consumer products.
- Quality Assurance: Routine batch testing to ensure products consistently meet purity requirements.
- Regulatory Compliance: Demonstrates to relevant authorities and certifying bodies that carbon black products conform to allowable limits for extractables.
Related Standards
Several other documents provide context or additional requirements related to carbon black extractables and material purity for food contact applications:
- ASTM D4483: Practice for evaluating precision for test method standards in the rubber and carbon black manufacturing industries.
- German Federal Communications: Key references on the testing and purity of carbon black used in plastics and food applications (e.g., Mitteilung BGesundhBl. 18, 268 (1972); 31, 363 (1988)).
- International Norms: ASTM standards harmonize with guidelines from the World Trade Organization Technical Barriers to Trade (TBT) Committee, ensuring international acceptance and compliance.
Keywords: ASTM D7772-15, carbon black extractables, cyclohexane extract, absorbance measurement, UV spectrophotometer, food contact materials, material screening, regulatory compliance, quality control, international standards