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Test Content
The Limiting Oxygen Index (LOI) represents the minimum oxygen level in the atmosphere that can sustain a thermoplastic flame. The higher the LOI value, the higher the incombustibility.
Test range
The limiting oxygen index test is suitable for the determination of combustion properties of plastics, rubber, paper, textiles, etc.
Test method
The test sample was placed vertically in a glass cylinder and an oxygen/nitrogen environment was established by a gas flow at the bottom of the cylinder. Ignite the top edge of the test sample and reduce the oxygen concentration in the gas stream until the flame is no longer supported.
Schematic diagram of the LOI test [1]
LOI calculation formula
LOI =[O2 / (O2+N2)] × 100
O2 and N2 are the minimum (oxygen and nitrogen, respectively) concentrations in the influent gas that pass the minimum burn length criterion.
Unit of LOI: Percentage, %
Commonly used limiting oxygen index test standards
There are many factors that affect the results of the limiting oxygen index test, including but not limited to gas flow rate, oxygen concentration control and purity, sample size and preparation, pressure control, temperature, plasticizers and fillers, etc.
At Alfa Chemistry, experienced materials chemists will recommend and select appropriate test standards for you based on customer needs and specific products.
- ASTM D2863
Standard Test Method for Measuring the Minimum Oxygen Concentration to Support Candle-Like Combustion of Plastics (Oxygen Index)
- ISO 4589-2
Plastics-Determination of burning behavior by oxygen index-Part 2: Ambient-temperature test
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Research Information
LOI for flammability comparison
LOI values are often used to compare the combustion performance of materials. For example, Seyfullah Madakbaş et al. prepared polyacrylonitrile (PAN)/hexagonal boron nitride (h-BN) composites. In this work, the researchers investigated the effect of h-BN on the flame retardancy of PAN in combination with LOI testing and other methods, confirming the improved flame retardancy and thermal stability. [2]
LOI values and SEM image of flame retardant composites [2]
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References
- Muhammad Maqsood. (2020). "Biodegradable Flame Retardants for Biodegradable Polymer," Biomolecules 10(7), 1038.
- Seyfullah Madakbaş, et al. (2013). "Preparation and thermal properties of polyacrylonitrile/hexagonal boron nitride composites," Thermochimica Acta 552, 1-4.
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