The Limiting Oxygen Index (LOI) test is a widely used method for evaluating the flammability resistance of materials. The test has been in use for many years in the plastics industry, and although now considered relatively unsophisticated due to the development and standardization of more elaborate methods, LOI testing continues to be an important screening and quality control method. The Kemgard® laboratory is equipped for LOI testing (according to the ASTM D2863 standard), and LOI results are routinely included in our published application bulletins.
|
The LOI test essentially measures the minimum oxygen concentration needed to support combustion of a specific material. A chamber is used to systematically vary the oxygen concentration in the vicinity of a burning material, and the minimum or limiting oxygen concentration needed for continued combustion is recorded. More flammable materials will continue burning at lower oxygen concentrations than will a less flammable material. Thus, conversely, a higher limiting oxygen concentration or LOI indicates a more flame resistant material.
|
The following example would be considered typical for a PVC wire insulation application using Kemgard® 911A.
| |
LOI (%) |
| without flame retardent |
28 |
| 1 phr Kemgard® 911A |
31 |
| 1 phr anitmony oxide |
31 |
| phr=parts per hundred parts resin |
|
|
| These results show that the addition of Kemgard® 911A significantly increases LOI and thus improves flammability resistance versus a system without flame retardants. The results also show how Kemgard® can be used to form the basis of antimony oxide free systems for improved environmental and health characteristics. |
