ISO 15825:2017 pdf – Rubber compounding ingredients — Carbon black — Determination of aggregate size distribution by disc centrifuge photosedimentometry.
5 Apparatus 5.1 Disc centrifuge photosedimentometer (DCP) 1) , capable of rotational speeds of 1 000 r/min to 11 000 r/min or greater, with integral spin feed-back control (accuracy and stability of rotational speed better than ± 0,05 %), spin fluid volume from 10 cm 3 to 20 cm 3 , stable temperature of spin fluid, stroboscope to monitor the rotating disc both for stability and streaming anomalies, and an appropriate optical turbidity measuring device. 5.2 Energy meter, capable of measuring the energy consumption (in kWh) of the probe-type sonicator. The energy meter is inserted between an electrical plug of the laboratory and the plug of the power supply cord of the sonicator. The actual energy consumption is indicated on a digital display. 5.3? Probe-type? sonicator 2) , typically with a nominal power of 200 W or more. The sonicator should be capable of providing a measured power consumption of at least 60 W. This has been found to be an effective means of dispersing carbon black into discrete aggregates. See Clause 8 for further details. NOTE Cylindrical tips with 12,7 mm (1/2 inch) diameter have been found to be suitable. 6 Reagents and materials Unless otherwise stated, use only reagents of recognized reagent grade 3) . 6.1 Water, distilled or deionized, grade 3 as defined in ISO 3696. 6.2 Ethanol, absolute. 6.3 Surfactant, non-ionic type 4) , 0,02 % to 0,05 % (by mass) solution. 6.4 Dodecane, ≥ 98 % purity (GC grade). 6.5? Spin? fluid: Water (6.1) containing surfactant (6.3) which may be adjusted to pH 9,0 to pH 10,0 using 0,1 mol/dm 3 NaOH. 6.6 Dispersion? fluid: A solution of 20 cm 3 of ethanol (6.2) and 80 cm 3 of water (6.1) containing a surfactant (6.3). The solution may be adjusted to a pH value between 9,0 and pH 10,0 using 0,1 mol/dm 3 NaOH.
7 Sampling Select carbon black samples from larger-sized lots at random, in either pelletized or non-pelletized form, in accordance with ISO 1124. Label and retain samples for storage or further analysis. 8 Calibration 8.1 The following procedure shall ensure that carbon black agglomerates are completely dispersed into aggregates. 8.2 Prepare a sample of ITRB (or ITRB−2) following the instructions in Clause 9. 8.3 Select sonication energy and sonication mode (e.g. pulsed mode) in such way that 0,005 kWh (18 kJ) are applied. This can typically be achieved by a power of 60 W and a sonication time of 5 min. 8.4 Start sonication and press on start button of the energy-meter, which is plugged in between supply plug and plug of the power cord of the sonicator. 8.5 Stop sonication after 5 min, press stop button on energy-meter and read energy consumption, expressed in kWh. 8.6 If the ITRB or ITRB−2 is entirely dispersed, it will give a mean Stokes diameter (“Mean”) of 105 nm ± 5 nm (99 nm ± 5 nm for ITRB−2). 8.7 Test ITRB or ITRB−2 as a standard carbon black on a regular basis before testing actual samples. 8.8 If the value of the standard is too high, increase sonication time and/or power or change the tip of the sonicator. NOTE The tips of the sonicator are consumed with time. 9 Preparation of test sample 9.1 Weigh 20 mg of carbon black in a weighing vessel. If the software cannot handle high turbidity values, reduce the sample mass. 9.2 Add to 20 cm 3 of dispersion fluid (6.6). 9.3 Disperse with ultrasonic energy for the time found during calibration (Clause 8), with the dispersing container immersed in a cooling medium, such as iced water, to minimize the heating effect of the sonic energy during sonication. The temperature of the test sample shall be approximately the same as ambient temperature, to minimize thermal gradients in the disc. Test samples shall be subjected to further sonication if there is any indication of streaming, or more than 1 h has elapsed since sonication.
11 Initiation of procedure 11.1 Set the rotational speed. In general, 8 000 r/min to 11 000 r/min for reinforcing grades and 4 000 r/min to 6 500 r/min for semi-reinforcing grades is suitable. Prior to the test, a 30 min warm-up phase at the chosen speed is necessary. Make sure that the spin fluid used in 11.3 is at room temperature. Keep the air filter of the test instrument clean at all time so that a temperature rise at the rotating disc cell during testing is avoided. NOTE Effective air ventilation can be achieved by keeping the ventilation window of the instrument open. 11.2 Inject 1,0 cm 3 of ethanol (6.2) and start the centrifuge. 11.3 Inject carefully 15 cm 3 of the spin fluid (6.5) to underlay the ethanol. 11.4 Inject 0,1 cm 3 of dodecane (6.4) on top of the gradient layer to reduce evaporative cooling. 11.5 Allow stabilization of spin fluid, typically for 3 min. 11.6 Set turbidity to zero on the DCP photodetector, if required. This step may be optional, depending on the instrument used in the procedure. The use of “cut” and “boost” controls is not recommended since it leads to poor reproducibility of the test results. 11.7 Inject 0,25 cm 3 of the test sample, prepared as in Clause 9, into the spinning disc, and immediately start the computer for data acquisition. For injecting the test sample, it is recommended to use a syringe with a needle having an inner diameter of 1,19 mm (16 gauge). 11.8 Read the temperature of the chamber measured by the integrated thermocouple. 11.9 Inspect the disc for hydrodynamic instability or streaming, which may be seen as vortices of sample originating from the dark band of layered carbon black, spiralling towards the outer boundary of the spin fluid. A normal run will produce a smooth, diffuse, circular band of carbon black moving outward towards the perimeter of the disc.