Fire Resistance of Plastics: Limiting Oxygen Index (LOI) tester ISO 4589-2

Oxygen index refers to the minimum oxygen concentration required for a material to burn with a flame in an oxygen-nitrogen mixed gas flow under specific test conditions. It is expressed as a volume fraction and is an important indicator for evaluating the combustion performance of a material. The higher the limiting oxygen index, the more difficult the material is to burn. It is generally believed that materials above 27% are difficult to burn, and materials below 20% are flammable.

Principle and method of the Limiting Oxygen Index Tester:

1. Principle:

Under specified conditions, ignite the material in an oxygen-nitrogen mixed gas flow and measure the minimum oxygen concentration required to maintain its combustion.

2. Method:

Oxygen index meter: Use oxygen and nitrogen mixed in proportion, accurately control the gas flow rate, and measure the minimum oxygen concentration required to maintain the combustion of the sample.

3. Test standard:

Different materials and application scenarios have different test standards, such as ISO 4589-2 (room temperature oxygen index) and ISO 4589-3 (high temperature oxygen index).

Technical parameters:

• Inner diameter of combustion tube 90mm.
• Height of combustion tube 450mm.
• Diameter of the tube hole at the tail end of the long rod igniter: φ2±1mm.
• Flow meter: 160～1600L/H adjustable.
• Pressure gauge accuracy is 2.5 levels.
• Pressure gauge resolution: 0.01MPa.
• Resolution of oxygen concentration indicator: 0.1%.
• Oxygen sensor: High-precision oxygen sensor imported from Germany.
• Gas source: Oxygen specified in GB3863, nitrogen specified in GB3864.
• Test environment: temperature 10-35℃, humidity 45-75%.
• Input pressure: 0.2- 0.3MPa.
• Working pressure: 0.05- 0.15MPa.
• Sample type: self-supporting material and non-self-supporting material.

Specification: