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What is the ISO standard for limiting oxygen index?



ISO 4589 "Plastics - Determination of burning behaviour by oxygen index" is a standard developed by the International Organisation for Standardisation (ISO) for the determination of the oxygen index for the burning behaviour of plastics. The standard provides a method for evaluating the burning behaviour of plastics, particularly under oxygen-limited conditions.

Key points of the ISO 4589 standard include:

1. Specimen preparation: Specimens of specific size and shape are prepared according to the standard. The size and shape of the specimen may be determined according to the required test conditions and application.
2. Oxygen index test device: Use of an oxygen index test device, which consists of a combustion chamber with controlled oxygen concentration and an appropriate ignition system.
3. test procedure: the specimen is placed in the combustion chamber and the process of burning the specimen is then controlled and recorded. Under restricted oxygen conditions, the specimen is observed for self-sustained combustion by varying the oxygen concentration to gradually reduce the oxygen supply.
4. Oxygen Index Calculation: The oxygen index is calculated based on the oxygen concentration at which the specimen burns and the duration of the combustion. The oxygen index is the oxygen concentration (expressed as a percentage by volume) at which the specimen can sustain combustion only under conditions of ignition by an ignition source.
The oxygen index results of ISO 4589 can be used to assess the burning behaviour and fire safety of plastic materials in case of fire. Higher oxygen index values indicate that the material is more difficult to burn under oxygen-limited conditions and has better flame-retardant properties.
It should be noted that different types of plastics may need to follow different parts of the applicable ISO 4589, e.g. ISO 4589-2 applies to specimens with a thickness greater than 10 mm. Therefore, before performing ISO 4589 testing, the requirements of the applicable standard should be carefully read and followed to ensure accuracy and comparability.

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