BS ISO 2007:2018 pdf download – Rubber, unvulcanized — Determination of plasticity — Rapid-plastimeter method
5.1.2 Means for moving one or other of the two platens normal to its surface, to compress the test piece to a thickness of 1,00 mm ± 0,01 mm. The mode of movement of the platen and the forces applied in this operation shall be such that, with or without the test piece in place, the movement is always completed within a period of 2 s. A force of at least 300 N is required and can be conveniently provided by springs.
5.1.3 Means of applying to one or other platen a test force of 100 N ± 1 N normal to its surface to compress the test piece.
5.1.4 Means for indicating the thickness of the test piece to the nearest 0,01 mm when it is between the platens.
5.1.5 Timing device, so that the test can be timed in seconds to an accuracy of 0,2 s.
5.1.6 Heating device and temperature control system, capable of maintaining the temperature of the upper and lower platens and that of the platens to within ±1 °C of the test temperature. 5.2 Punch, capable of producing test pieces of approximately constant volume quickly and without difficulty. The punch shall consist of a flat-ended cylindrical anvil and a coaxial tubular knife, moving independently of one another. A single action of the handle shall compress a portion of the material to a thickness of 3,4 mm ± 0,2 mm and shall cut out a disc of approximately 13 mm diameter. Figure 2 is a schematic diagram of a punch.
5.3 Bleached, unglazed, acid-free tissue paper, of approximately 17 g/m 2 or cigarette paper of about 22 g/m 2 to 26 g/m 2 , cut into two equal pieces. Both papers shall use the dimension of 30 mm × 45 mm. For interlaboratory testing, paper from the same source shall be used.
6 Test piece Raw rubber shall be homogenized when comparative tests are carried out. The preparation and homogenization of the sample shall be carried out in accordance with the provisions of ISO 1795.
The test piece shall be a disc of rubber approximately 13 mm in diameter and with a thickness of 3,4 mm ± 0,2 mm. If the specified thickness is attained by compressing an initially thicker sheet, the latter shall be not more than 3,6 mm thick. Prepare three test pieces for the determination of plasticity number. The sample shall be conditioned at 25 °C ± 5 °C, for a minimum of 1 h before testing. The test pieces cut from conditioned test samples may be tested immediately. The conditioning in a standard laboratory temperature is strongly recommended. 7 Calibration The settings of the rapid plastimeter shall be checked against the manufacturer’s instructions. In the absence of this, the loading spring (100 N ± 1 N) and the timing unit (pre-heating time 15 0 1 + s and test period 15 s ± 0,2 s) shall be calibrated in accordance with ISO 18899.
The position of the top platen shall be checked before each test. A sample of standard butyl or Constant Viscosity natural rubber can be used to check whether the machine is in working order. The test pieces shall in this case be prepared from a sheet of 3,4 mm ± 0,2 mm thick, cut from the standard butyl or Constant Viscosity natural rubber. Alternatively, test piece NBS-388 of National Institute of Standard and Technology (NIST) can be used as a standard material for calibration.
8 Temperature of test
Unless otherwise stated, the test shall be carried out at 100 °C ± 1 °C.
Place two pieces of tissue paper or cigarette paper (5.3), between the heated platens (5.1.1) and set the thickness-measuring device (5.1.4) to zero when the platens are closed. Insert the test piece centrally between the two pieces of tissue paper or cigarette paper, and place the whole between the heated platens. Compress the test piece to a thickness of 1,00 mm ± 0,01 mm with the platen-moving device (5.1.2), and hold it in the compressed state for a pre-heating period of 15 0 1 + s. On completion of the pre-heating period, apply a test force of 100 N ± 1 N to the movable platen for a period of 15 s ± 0,2 s with the force-application device (5.1.3). At the end of this time, measure the thickness of the test piece. Take the reading of thickness at the moment the 15 s test period is completed. On models with electronic digital read-out, the measurement shall be held until the instrument is re- set. On instruments with dial gauge read-out, the reading shall be taken immediately before any drop- back occurs, and before the locking mechanism operates.