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Limiting Oxygen Index
Limiting Oxygen Index (LOI)
The Limiting Oxygen Index (LOI) is a quantitative measure of a material’s flammability. It is defined as the minimum concentration of oxygen, expressed as a percentage, that will support the combustion of a material. The LOI test is widely used to assess the flammability characteristics of polymers and other materials.
The LOI test determines the minimum concentration of oxygen in a mixture of oxygen and nitrogen that is required to sustain the burning of a material. Materials with higher LOI values are less flammable because they require a higher concentration of oxygen to continue burning.
- Material Selection: Used in selecting materials for applications where fire resistance is critical, such as construction, automotive, aerospace, and electronics.
- Quality Control: Employed in the quality control of materials to ensure they meet flammability standards and regulations.
- Research and Development: Used in R&D to develop new materials with improved fire-resistant properties.
- Regulatory Compliance: Helps manufacturers comply with flammability standards set by regulatory bodies.
- Quantitative: Provides a precise numerical value indicating flammability.
- Simple: Relatively straightforward and quick to perform.
- Comparative: Allows easy comparison of the flammability of different materials.
- Standardized: Widely recognized and standardized by various organizations (e.g., ASTM D2863, ISO 4589).
Samples for Limiting Oxygen Index (LOI) testing should be uniform in size, typically 70 mm long, 6.5 mm wide, and 3 mm thick, and must be clean and dry. Multiple replicates are needed to ensure reliability, and samples should be stored and handled in a controlled environment to maintain their properties. Proper labeling and preparation are essential for accurate and consistent results.