IEC 60811-605 pdf download.Electric and optical fibre cables – Test methods for non-metallic materials
4 Test method
4.1 General This part of IEC 6081 1 shall be used in conjunction with IEC 6081 1 -1 00. Unless otherwise specified, tests shall be carried out at room temperature. 4.2 Method A – Measurement of carbon black and/or mineral filler content in polyethylene by direct combustion 4.2.1 Sample and test piece preparation A sample of the outer covering or sheath of sufficient weight shall be taken from one end of the cable. The sample shall be cut in pieces, the dimensions of which shall not exceed 5 mm in any direction. 4.2.2 Test procedure A combustion boat about 75 mm long shall be heated until it is red hot, allowed to cool in the desiccator for at least 30 min and weighed to the nearest 0,000 1 g. A sample of polyethylene weighing (1 ,0 ± 0,1 ) g shall be placed in the boat and the whole weighed to the nearest 0,000 1 g. The weight of the boat shall be subtracted to give the weight of the polyethylene to the nearest 0,000 1 g (quantity A). The boat and the sample shall then be placed in the middle of a hard glass, silica or porcelain combustion tube, with a bore approximately of 30 mm, and (400 ± 50) mm in length. A stopper carrying a thermometer for temperature measurements from 300 °C to 650 °C and a tube for the admission of nitrogen shall then be inserted into one end of the combustion tube so that the end of the thermometer touches the boat. Nitrogen with an oxygen content of less than 0,5 % shall be passed through the combustion tube at (1 ,7 ± 0,3) l/min and this rate of flow shall be maintained during the subsequent heating. In case of doubt, the oxygen content of the nitrogen shall be limited to 0,01 %. The combustion tube shall be placed in a furnace and its outlet connected to two cold traps in series, both containing trichlorethylene, the first being cooled with solid carbon dioxide. The outlet tube from the second trap shall lead to a fume hood or the outside atmosphere. Alternatively, it is permissible for the outlet from the combustion tube to lead directly to the outside atmosphere.The furnace shall then be heated so that the temperature is between 300 °C and 350 °C after about 1 0 min; about 450 °C after another 1 0 min and (600 ± 5) °C after a third period of 1 0 min. This temperature shall then be maintained for 1 0 min, at the end of which the outlet tube shall be disconnected from the cold traps, if these are used, and the tube containing the boat withdrawn from the furnace and allowed to cool for 5 min, the flow of nitrogen being maintained at the same rate as before. The boat shall then be removed from the combustion tube through the nitrogen inlet end, allowed to cool in the desiccator for 20 min to 30 min and then re-weighed. The weight of the residue is determined to the nearest 0,000 1 g (quantity B of residue). Subsequently, the boat shall again be introduced into the combustion tube; instead of nitrogen, air or oxygen shall be blown through the tube at an adequate flow rate for a temperature of (600 ±20) °C, and the remaining carbon black shall be burnt. After it has cooled in the test assembly, the boat shall be removed and weighed again. The mass of the residue is determined to the nearest 0,000 1 g (quantity C of residue).NOTE 1 A starting temperature of 1 00 °C is practical, as the subsequent measurements can be carried out earlier because of the shorter cooling time. At first, purge the test specimen with dry nitrogen with an oxygen content as described in 4.3.2. When the temperature of 850 °C is reached, switch from dry nitrogen to “synthetic air”. With the switch to air, the combustion of the carbon black that is present will follow. NOTE 2 Weight loss during the purging stage with nitrogen, up to approximately 800 °C, is due to degradation of the polymer and loss of other minor ingredients.
IEC 60811-605 pdf download
