LOI stands for Limiting Oxygen Index, while UL94 is a standard developed by the Underwriters Laboratories for flammability testing of plastic materials. Both the LOI and UL94 tests are used to measure the flammability of plastics and determine their ability to resist ignition and flame spread.
The primary difference between LOI and UL94 lies in the testing method and the measurements used to determine flammability. The LOI test measures the minimum concentration of oxygen required to sustain combustion, and the results are typically reported as a percentage. The higher the LOI value, the more difficult it is for the material to ignite and sustain combustion.
On the other hand, the UL94 test involves subjecting a plastic sample to a flame of a specified size and duration and observing its performance under a series of test methods. The procedure includes horizontal and vertical burning tests as well as a test for the self-extinguishing performance of the material after it is removed from the flame source. The UL94 test utilizes an alphanumeric rating system, ranging from V-0 to HB, that classifies the material based on its level of resistance to ignition and flame spread.
In summary, the LOI test measures the oxygen concentration required to sustain combustion, while the UL94 test is a comprehensive flammability test that incorporates different scenarios and measures the material's resistance to ignition and flame spread under different conditions.