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Oxygen Index Test

Oxygen Index Apparatus/LOI (Limitation Oxygen Index tester) is widely used to measure burning performance of plastics, rubber, fiber, foam, softening sheet, film etc.,

The Oxygen Index is, perhaps, the most economical and precise quality control test of combustible materials. Its ease of use together with high levels of precision has made this technique a primary characterising and quality control tool to the plastic and electric cable industries and it has been specified by several military and transport groups. The technique measures the minimum percentage of oxygen in the test atmosphere that is required to marginally support combustion.

UnitedTest Oxygen Index Testing Equipment

Feature:

  • Touching screen
  • Imported high accuracy oxygen sensor

Key parameter:

  • Gas flow rate: 12.1L/min
  • Temperature range: 200 ℃
Details

Oxygen Index Test Apparatus

Model: YZS-100A, YZS-100B

Feature:

  • Digital display
  • Imported high accuracy oxygen sensor

Key parameter:

  • Burning tube inner diameter: 100mm
  • Burning tube height: 450mm
Details

What's the oxygen index test (LOI)?

Oxygen Index (OI) Value refers to the minimum concentration of oxygen required for a material to sustain flaming combustion in an oxygen-nitrogen mixed flow under specified test conditions, expressed as the volume percentage of oxygen. 


The oxygen index is a key indicator of a material's combustion performance. The higher the value, the less flammable the material and the better its flame-retardant performance; conversely, the lower the oxygen index, the more easily the material burns.  For example, materials with an oxygen index below 21% are considered flammable, while materials with an oxygen index above 27% are generally regarded as flame-retardant. 


Oxygen index test is a standardized method used to determine a material's oxygen index. This test controls the concentration of the oxygen-nitrogen gas mixture to identify the minimum oxygen concentration at which the material can sustain flaming combustion. Common testing standards include international standards ISO 4589, ASTM D2863. 


The testing apparatus mainly includes a combustion tube, sample holder, flow control system, and igniter. 

Samples are usually held vertically in the combustion tube. After ignition, the oxygen concentration is gradually reduced until the flame goes out, allowing the oxygen index to be calculated. 


The oxygen index test has important applications in materials science and engineering, such as evaluating the flame-retardant performance of plastics, rubber, textiles, and aerospace materials, providing a basis for product safety certification and fireproof design. It should be noted that the oxygen index is affected by factors such as temperature, humidity, and material dimensions, so testing conditions must be strictly controlled to ensure accurate results.


Oxygen Index Testing
Limitation Oxygen Index tester

Test Procedure

Test Procedure:

A small test specimen is supported vertically in a mixture of oxygen and nitrogen flowing upwards through a transparent chimney. The upper end of the specimen is ignited and the subsequent burning behaviour of the specimen is observed to compare the period for which burning continues, or the length of the specimen burnt, with specified limits for such burning. By testing a series of specimens in different oxygen concentrations, the minimum oxygen concentration is estimated. 


Test Sample information:

    Complete test series:

Sample quantity: 20 samples

Dimensions: 80 – 150 mm x 10 mm, thickness 4 or 10 mm.

 

    Reduced test series, one specified oxygen concentration

Sample quantity: 8 samples

Dimensions: 80 – 150 mm x 10 mm, thickness 4 or 10 mm.

limitation oxygen index LOI ASTM D2863
Oxygen Index Apparatus

Principle and standard

Principle:  A small test specimen is supported vertically in a mixture of oxygen and nitrogen flowing upwards through a transparent chimney. The upper end of the specimen is ignited and the subsequent burning behaviour of the specimen is observed to compare the period for which burning continues, or the length of the specimen burnt, with specified limits for such burning. By testing a series of specimens in different oxygen concentrations, the minimum oxygen concentration is estimated.


ISO 4589-2  " Plastics -- Determination of burning behaviour by oxygen index -- Part 2: Ambient-temperature test”

ASTM D2863  " Standard Test Method for Measuring the Minimum Oxygen Concentration to Support Candle-Like Combustion of Plastics (Oxygen Index) “

NES 714, EN 45545-2. etc.,


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