The oxygen index test is a test method used to measure the flammability of plastics and other materials. The test determines the minimum concentration of oxygen in a mixture of oxygen and nitrogen that is needed to support combustion of the material being tested. The higher the oxygen index value, the less likely the material is to ignite and sustain a fire.
During the test, a sample of the plastic material is held vertically in a test chamber and exposed to a mixture of oxygen and nitrogen gases. The oxygen concentration is gradually decreased until the material stops burning. The oxygen concentration at this point is called the oxygen index. The test is typically repeated multiple times to ensure accuracy.
The oxygen index test can provide valuable information about the flammability of a plastic material, which can be useful in determining its suitability for specific applications. For example, materials used in aircraft interiors may be required to have a high oxygen index to minimize the risk of fire in the event of an accident.
It is important to note that the oxygen index test is only one of several tests used to evaluate the flammability of plastics. Other tests, such as the UL 94 test and the ASTM D635 test, may also be used to assess a material's flammability characteristics.