(ISS)Investigation about the fire safety evaluation of the electric wire using LOI method


One of the flammability test methods to evaluate the incombustibility of plastic materials is Limiting Oxygen Index (LOI) method[1]. We can get LOI from LOI method. LOI means minimum oxygen concentration for materials to keep flaming under the specified condition by ISO 4589-2, which is known as one of plastic material flammability characteristics.

One of the potential cause of fire in space craft is a combustion of electric wire insulation. Now, the fire safety of electric wire intended to use in a space craft is evaluated by NASA-STD-6001[2] on the ground. However, the evaluation results is given as Pass/Non pass, which is valid only for specific condition. Further, the scientific backgrounds of the test method is questionable because the test is done in 1G while being low gravity in spacecraft. 

LOI method is usually used for polymer materials like plastic. In this research, we consider whether this LOI method can be used for fire safety evaluation of the electric wire. If LOI method can be used for the purpose, and we can find relation of LOI and electric wire insulation flammability, many existing flammability data based on LOI method become useful for evaluation of fire safety of electric wire.



In this research, the relation of flammability of polymer materials and the electric wire with the same polymer insulation is investigated in terms of material shape, core material, insulation thickness. The experimental apparatus is shown in the following figure.



[1] ISO 4589-2, Plastics-Determination of burning behavior by oxygen index Part2: Ambient-temperature test

[2] NASA-STD-6001, Flammability, Offgassing、 and Compatibility Requirements and Test Procedures


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