ISO 4589-2:1996 download free.Plastics-Determination of burning behaviour by oxygen index Part 2 : Ambient-temperature test.
1 Scope
This part of ISO 4589 specifies methods for
determining the minimum concentration of oxygen, in admixture with nitrogen, that will support
combustion of small vertical test specimens under specified test conditions. The results are defined as oxygen index values.
Methods are provided for testing materials that are self-supporting in the form of vertical bars or sheet up to 10,5 mm thick. These methods are suitable for solid, laminated or celluar materials characterized by an apparent density greater than 100 kg/rn3. The methods may also be applicable to some cellular
materials having an apparent density of less
than 100 kg/rn3. A method is provided for testing flexible sheet or film materials while supported
vertically.
For comparative purposes, a procedure is provided for determining whether or not the oxygen index of a material lies above some specified minimum
value.
Oxygen index results obtained using the methods described in this part of ISO 4589 can provide a
sensitive measure of the burning characteristics of materials under certain controlled laboratory
conditions, and hence may be useful for quality control purposes. The results obtained are
dependent upon the shape, orientation and isolation of the test specimen and the conditions of ignition. For particular materials or applications, it may be necessary or appropriate to specify different test
conditions. Results obtained from test specimens of differing thickness or by using different ignition
procedures may not be comparable and no
correlation with flammability behaviour under other fire conditions is implied.
Results obtained in accordance with this part of ISO 4 589-2 must not be used to describe or appraise the fire hazard presented by a particular material or
shape under actual fire conditions, unless used as one element of a fire risk assessment that takes into account all of the factors pertinent to the
assessment of the fire hazard of a particular application for the material.
NOTE 1 It may not be possible to apply these methods
satisfactorily to materials that exhibit high levels of shrinkage
when healed. e.g. highly oriented thin film.
NOTE 2 For assessing the flame propagination properties of celluar materials of density < 100 kg/rn3, attention is drawn to the method of ISO 3582:2000. Flexible cellular polymeric
makrkils — Laboratory asse8sment of horizontal burning
characteristics of small specimens subjected to a small flame. jj
Alternatively, for comparison with a specified minimum oxygen index value, three test specimens are tested using the relevant oxygen concentration, at least two of which are required to extinguish before any relevant burning criterion is exceeded.
5 Apparatus
5.1 Test chimney, consisting of a heat-resistant glass tube supported vertically on a base through which oxygen-containing gas mixtures can be introduced (see Figure land Figure 2).
Ii The preferred dimensions of the chimney are 500 mm ± 50 mm minimum height and 75 mm to 100 mm inside diameter. J
The upper outlet shall be restricted as necessary by an overhead cap having an outlet small enough to produce an exhaust velocity of at least 90 mm/s from that outlet.
NOTE 3 A cap converging to an outlet of 40 mm diameter at a level at least 10 mm above the top of the cylindrical chimney has been found satisfactory.
Chimneys of other dimensions, with or without restricted outlets, may be used, if shown to give equivalent results. The bottom of the chimney, or the base upon which the chimney is supported, shall incorporate a device for distributing evenly the gas mixture entering the chimney. The preferred device comprises a suitable diffuser and a mixing chamber with metal foil. Other devices, such as radial manifolds, may be used, if shown to give equivalent results. A porous screen may be mounted below the level of the specimen holder, to prevent falling combustion debris from fouling the gas entry and distribution paths.
The chimney support may incorporate a levelling device and indicator, to facilitate vertical alignment of the chimney and a test specimen supported therein. A dark background may be provided to facilitate observation of flames within the chimney.
5.2 Test specimen holder, suitable for supporting a specimen vertically in the centre of the chimney.
For self-supporting materials, the specimen shall be held by a small clamp which is at least 15 mm away from the nearest point at which the specimen may burn before the extent.of.burnmg criterion is exceeded. For supported film or sheet test specimens, the specimen shall be supported by both vertical edges in a frame equivalent to that illustrated by Figure 2, with reference marks at 20 mm and 100 mm below the top of the frame.
The profile of the holder and its support should preferably be smooth to minimize induction of turbulence in the rising flow gas.
5.5 Flame igniter, comprising a tube that can be inserted into the chimney to apply to the test specimen a flame issuing from an outlet of 2 mm ± 1 mm diameter at the end of the tube. The flame fuel shall be propane, without premixed air. The fuel supply shall be adjusted so that the flame will project 16 mm ± 4 mm vertically downwards from the outlet when the tube is vertical within the chimney and the flame is burning within the chimney atmosphere.
5.6 Timing device, capable of measuring periods up to 5 mm with an accuracy of ± 0,5 a.
5.7 Fume extraction system, providing sufficient ventilation or exhaust to remove fumes or soot expelled from the chimney without disrupting the gas flow rate or temperatures in the chimney.
NOTE 6 If soot-generating materials are being tested, the glass chimney may require cleaning to maintain good visibility, and the gas inlets, or inlet screen, and temperature sensor (if fitted) may also require cleaning to function properly. Suitable precautions should be taken to protect personnel from noxious materials or burns during testing or cleaning operations.
5.8 Tool for preparing rolled film, consisting of a stainless-steel rod of 2 mm diameter, with a slit in one end (see Figure 3).
6 Calibration of equipment
For compliance with this method, calibrate the equipment periodically in accordance with the instructions given in annex A so that the maximum interval between recalibration and use complies with the periods stated in Table 1.
7 Preparation of test specimens
7.1 Sampling
Obtain a sample sufficient for preparation of at least 15 test specimens. The sample shall be taken, if relevant, in accordance with the material specification, otherwise in accordance with ISO 2859-1 or ISO 2859-2, as applicable.
NOTE 7 For a material for which the oxygen index is known to within * 2., 15 test specimens may be sufficient. For materials of unknown oxygen index, or which exhibit erratic burning characteristics, between 15 and 30 test specimens may be required.
8.4 Selecting successive oxygen concentrations
The procedure described in 8.5 and 8.6 is based upon the “up-and-down method for small samples”, using the specific case where NT — Nb = 5 (see 8.6.2 and 8.6.3). with an arbitrary step size for certain changes to be made in the oxygen concentration used.
During the testing, select the oxygen concentration to be used for testing the next test specimen as follows:
a) decrease the oxygen concentration if the burning behaviour of the preceding specimen gave an “X” response;
otherwise
b) increase the oxygen concentration if the preceding specimen gave an “0” response.
Choose the size of the change in oxygen concentration in accordance with 8.5 or 8.6. as appropriate.
8.5 Determining the preliminary oxygen concentration
Repeat the procedures specified in 8.1.4 to 8.4 inclusive, using oxygen concentration changes of any convenient step size, until the oxygen concentrations, in volume per cent, have been found that differ by  1.0 % (VIV) and of which one gave an “0” response and the other an “X” response. From this pair of oxygen concentrations, note that which gave the “0” response as the preliminary oxygen concentration level and then proceed in accordance with 8.6.
NOTE 19 The two results, at oxygen concentrations  1.0% (V/V) apart, which give opposite responses do not have to be from successive specimens.
NOTE 20 That concentration which gave the “0” response does not have to be lower than that which gave the “X” response. NOTE 21 A format convenient for recording the information required by this and subsequent clauses is illustrated in annex C.
8.6 Oxygen concentration changes
8.6.1 Using, again, the preliminary oxygen concentration (see 8.5). test one specimen by repeating 8.1.4 to 8.3 inclusive. Record both the oxygen concentration (ç) used and the response, “X” or “0”, as the first of the Nu and of the NT series of results.
8.6.2 Change the oxygen concentration, in accordance with 8.4. using concentration changes (d) of 0,2 % (VIV) (see note 22) of the total gas mixture to test further specimens in accordance with 8.1.4 to 8.4 inclusive, noting the values of c0 and the corresponding responses until a different response to that obtained in 8.6.1 is recorded.