Overview
SIST EN ISO 787-21:2018 specifies a general test method for assessing the heat stability of pigments and extenders using a stoving (high-temperature curing) medium. The standard enables manufacturers and laboratories to compare the heat resistance of pigments by detailing specific heating temperatures and durations. The procedure involves direct comparison with an agreed reference pigment sample. This standard forms part of the wider ISO 787 series, which collectively defines comprehensive testing methods for pigments and extenders.
With applications across paints, coatings, plastics, and related industries, this standard helps ensure product quality and reliability where pigments are exposed to elevated temperatures during processing or in end use.
Keywords: heat stability of pigments, pigment testing, ISO 787-21, stoving medium, pigment heat resistance, comparative test methods.
Key Topics
- Heat Stability Testing: The standard provides a framework for comparing the heat stability of a pigment sample versus a reference under agreed stoving conditions (temperature and time).
- Test Procedure: Involves preparing dispersions of both the test and reference pigment in a stoving medium, applying to panels, drying, stoving at defined temperatures, and visually comparing the resulting panels for color change.
- Controlled Environment: Specifies that comparisons are made under consistent lighting, either natural or artificial daylight, to minimize variability in color evaluation.
- Documentation and Traceability: Requires detailed reporting, including pigment identification, reference samples and media, test method details, test conditions, deviations from standard procedures, and the results of the comparative color change assessment.
- Flexibility and Agreement: The protocol calls for certain variables (medium, application method, exact temperature and time, reference pigment) to be mutually agreed upon by the parties involved, ensuring adaptability to different pigment types and applications.
Applications
The procedures defined in SIST EN ISO 787-21:2018 are critical for several practical scenarios:
- Paint and Coatings Manufacturing: Assists quality control departments in selecting heat-stable pigments for products cured at high temperatures, such as industrial enamels and automotive finishes.
- Plastics and Polymers: Helps determine the suitability of pigments for plastics processing, where pigments may be exposed to significant heat during molding or extrusion.
- Research and Development: Supports labs in developing and comparing new pigment formulations with improved heat stability or investigating the reliability of alternative suppliers.
- Specification Compliance: Provides third-party laboratories and regulatory bodies with a recognized methodology for verifying claims regarding pigment heat resistance according to international standards.
- Product Performance Assurance: Reduces the risk of discoloration or degradation in finished products by allowing manufacturers to pre-select pigments with proven stoving stability.
Related Standards
SIST EN ISO 787-21:2018 is part of the systematic approach of the ISO 787 series, covering general methods of test for pigments and extenders. Relevant related standards include:
- ISO 787-1: Comparison of color
- ISO 787-2: Determination of matter volatile at 105°C
- ISO 787-15: Comparison of resistance of colored pigments to light from a specified light source
- ISO 787-22: Comparison of resistance to bleeding of pigments
- ISO 3668: Visual comparison of color of paints
In combination, these standards offer a broad set of tools for evaluating pigment properties, enabling standardized product development and consistent quality control throughout the pigment and extender value chain.
