Overview
ISO 9117-5:2012, titled "Paints and varnishes - Drying tests - Part 5: Modified Bandow-Wolff test," is an international standard published by ISO that specifies a standardized method to determine whether coatings- including multi-coat systems-have reached various stages of drying. The standard also enables an assessment of the drying speed of these coatings. This method focuses particularly on the evaluation of the drying process stages using the Modified Bandow-Wolff test, which involves applying different weights and observing physical responses of the coating surface.
Notably, the standard highlights limitations when applied to plastic coatings due to their elasto-plastic behavior, which cannot be fully assessed by temporary visible changes on the surface during drying.
Key Topics
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Drying Stage Determination: The standard defines procedures for classifying coatings into drying stages 1 through 7, based on resistance to certain test actions using weights ranging from 20 g to 20 kg.
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Modified Bandow-Wolff Test Procedure:
- Application of glass spheres to assess early drying stages.
- Use of paper and rubber discs combined with precise loads to evaluate adhesion and surface changes under stress.
- Specific load and impact test requirements corresponding to each drying stage.
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Test Conditions and Equipment:
- Testing performed at controlled laboratory conditions (around 23 ± 2°C, ambient humidity).
- Use of standardized test panels (steel panels 150x95 mm).
- Equipment such as glass spheres, brushes, rubber discs of defined hardness, and weights of specified mass.
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Coating Preparation:
- Sample preparation follows ISO standards for sampling, panel selection, and wet film thickness measurements.
- Multi-layer coatings can also be assessed with this test method.
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Evaluation Limitations:
- Elasto-plastic coatings like plastics may not reach certain drying stages detectable by this test.
- Visual assessments can be influenced by surface gloss and texture, making interpretation more precise on glossy finishes.
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Reporting:
- Comprehensive test reporting requirements including product identification, test conditions, preparation details, drying stage results, anomalies, and any deviations from the standard method.
Applications
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Quality Control in Coating Production: ISO 9117-5:2012 provides manufacturers with a reliable method of verifying drying times and performance characteristics of paints and varnishes during formulation and production phases.
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Research and Development: Used by formulation scientists to compare drying speeds and optimize multi-coat systems for improved durability and efficiency.
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Surface Treatment Validation: Helps verify if coatings applied in industrial or automotive settings have dried sufficiently before subsequent handling or processing.
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Coating Performance Certification: Assists certification bodies in confirming compliance with drying time standards for protective and decorative coatings.
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Comparative Analysis: Enables benchmarking between different coating products or drying conditions.
Related Standards
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ISO 9117 series: Other parts cover complementary drying test methods:
- Part 1: Determination of dry-to-core time.
- Part 2: Pressure test for stackability.
- Part 3: Surface drying test using glass beads.
- Part 4: Mechanical recorder drying test.
- Part 6: Apparent complete drying test.
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ISO 1513: Examination and preparation of test samples.
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ISO 1514: Standard panels for coating tests.
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ISO 2808: Determination of paint film thickness.
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ISO 3270: Conditioning and testing ambient temperature and humidity.
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ISO 15528: Sampling of paints and varnishes products.
Summary
ISO 9117-5:2012 is a vital international standard that provides a practical, consistent, and repeatable method to measure the drying progression and speed of various paint and varnish coatings. By implementing the Modified Bandow-Wolff test, industries can ensure their coatings meet quality and performance expectations, optimize drying processes, and validate multi-layer coating applications. Understanding the limitations with plastically behaving coatings and combining this test with other drying assessments enhances overall evaluation accuracy.
Keywords: ISO 9117-5:2012, paint drying test, varnish drying stages, Modified Bandow-Wolff test, coating drying speed, multi-coat systems, paint quality control, drying assessment, film thickness measurement, paint testing standard.
