Overview
ISO 17564:2008 is an international standard developed by the International Organization for Standardization (ISO) that specifies a reliable analytical method for determining the residual unsaturation in raw hydrogenated nitrile rubber (HNBR). This is achieved by measuring the iodine value, which quantifies the degree of unsaturation present in the rubber sample. The method utilizes Wijs' solution, a halogen reagent, to react with the double bonds in the polymer chain. Accurate measurement of residual unsaturation is critical for quality control and performance assessment of HNBR materials used in various industrial applications.
Key Topics
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Scope of the Method
The standard defines a chemical titration procedure to determine the iodine value of raw HNBR, reflecting its residual unsaturation level.
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Principle of the Test
A known excess of Wijs' solution is added to a dissolved HNBR sample, allowing iodine to add across double bonds. Unreacted iodine is then quantified via titration with sodium thiosulfate, enabling the calculation of iodine value.
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Required Reagents and Apparatus
- Wijs' solution (prepared according to a specified procedure in Annex A)
- Chloroform solvent to dissolve HNBR
- Potassium iodide and starch solution for titration endpoint detection
- Standard volumetric sodium thiosulfate solution
- Laboratory equipment such as mechanical shaker, constant temperature bath, analytical balance, pipettes, and burette
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Procedure Highlights
- Selection of test portion sizes based on expected iodine values
- Dissolution of sample in chloroform
- Controlled reaction with Wijs' solution at 25 ± 1°C for defined times
- Titration to quantify unreacted iodine
- Blank titration to ensure accuracy of results
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Calculation
The iodine value is calculated using the volume difference between sample and blank titration, sample mass, sodium thiosulfate concentration, and iodine atomic mass factor.
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Precision Data
Annex B provides statistical precision information based on interlaboratory studies, defining repeatability and reproducibility parameters crucial for validating test results.
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Safety and Environmental Considerations
Due to hazardous chemicals involved (e.g., chloroform and iodine compounds), compliance with laboratory safety and environmental disposal protocols is emphasized.
Applications
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Quality Control in Rubber Manufacturing
Determining residual unsaturation helps manufacturers monitor and control the hydrogenation process of nitrile rubber, ensuring product consistency and desired chemical properties.
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Material Characterization
The iodine value indicates the degree of hydrogenation, which directly affects the thermal stability, chemical resistance, and mechanical strength of HNBR products.
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Research and Development
Enables comparative studies of different HNBR grades and optimization of hydrogenation techniques in R&D environments.
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Compliance and Standardization
Adoption of ISO 17564:2008 facilitates consistent and internationally accepted testing methods for HNBR residual unsaturation, promoting harmonization across the rubber industry.
Related Standards
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ISO 1795: Rubber, raw natural and raw synthetic - Sampling and further preparative procedures - referenced for sample collection and preparation.
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ISO/TR 9272:2005: Rubber and rubber products - Determination of precision for test method standards - provides framework for assessing precision of this and related test methods.
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ASTM D5902: Standard Test Method for Rubber - Determination of Residual Unsaturation in HNBR by Iodine Value - an alternative standard with similar methodology.
By following ISO 17564:2008, laboratories can accurately assess the residual unsaturation in raw hydrogenated nitrile rubber, ensuring materials meet stringent industrial specifications. The standard supports improved product performance and reliability through precise and reproducible iodine value determination.
Open preview (PDF)Raw hydrogenated nitrile rubber (HNBR) — Determination of residual unsaturation by iodine value
