ASTM D2863-17a pdf free download.Standard Test Method for Measuring the Minimum Oxygen Concentration to Support Candle-Like Combustion of Plastics (Oxygen Index).
1 .1 This fire-test-response standard describes a procedure for measuring the minimum concentration of oxygen, expressed as percent volume, that will just support flaming combustion in a flowing mixture of oxygen and nitrogen.
1.2 This test method provides three testing procedures. Procedure A involves top surface ignition. Procedure B involves propagating ignition, and Procedure C is a short procedure involving the comparison with a specified minimum value of the oxygen index.
1.3 Test specimens used for this test method are prepared into one of six types of specimens (see Table I).
1 .4 This test method provides for testing materials that are structurally self-supporting in the form of vertical bars or sheet up to 10.5-mm thick. Such materials are solid, laminated or cellular materials characterized by an apparent density greater than 15 kg/m3.
1.5 This test method also provides for testing flexible sheet or film materials, while supported vertically.
1 .6 This test method is also suitable, in some cases, for cellular materials having an apparent density of less than 15 kg/m3.
4.2 Three procedures are included in this test method. In Procedure A, a complete assessment of the oxygen index is conducted using top surface ignition. In Procedure B, a complete assessment of the oxygen index is conducted using propagating ignition. Procedure C provides a comparison with a specified minimum value of oxygen index and can be conducted using top surface ignition or propagating ignition.
5. Significance and Use
5.1 This test method provides for the measuring of the minimum concentration of oxygen in a flowing mixture of oxygen and nitrogen that will just support flaming combustion of plastics. Correlation with burning characteristics under actual use conditions is not implied.
5.2 In this test method, the specimens are subjected to one or more specific sets of laboratory test conditions. If different test conditions are substituted or the end-use conditions are changed. it is not always possible by or from this test to predict changes in the fire-test-response characteristics measured. Therefore, the results are valid only for the fire-test-exposure conditions described in this test method.
6. Apparatus
6. 1 Test Chimney. The test chimney consists of a heat- resistant glass tube of 75 to 100-mm inside diameter and 450 to 500-mm height. The opening at the top of the chimney shall he restricted to provide an outlet of 40 ± 2-mm diameter, either by providing an overhead cap or by designing the glass chimney appropriately. The bottom of the chimney, or the base to which the tube is attached, shall contain noncombustible material to evenly mix and distribute the gas mixture entering at this base. Glass beads 3 to 5 mm in diameter in a bed 80 to 100-mm deep have been found suitable. The chimney shall he mounted securely Ofl the base to prevent air leaks. One example of a design is shown in Fig. 1.
6.2 Specimen Holders
6.2. 1 Specim en Ho icier for Self ‘Supporting Specini ens— Any small holding device that will support the specimen at its base and hold it vertically in the center of the chimney is an acceptable specimen holder. A typical arrangement (see Fig. I) consists of a laboratory thermometer clamp inserted into the end of a glass tube held in place by glass beads or otherwise firmly supported.
6.2.2 Specimen Holder for Specimens of Flexible Sheet or Fil,,i Materials that Require Support—A specimen holder for flexible film or sheet materials that require support shall be able to support the specimen by both vertical edges in a frame equivalent to that illustrated by Fig. 2, with reference marks at 20 and 100 mm below the top of the frame. The profile of the holder and its support shall be smooth to minimize induction of turbulence in the rising flow of gas.ASTM D2863 pdf download.