ISO 20379:2018 pdf free
ISO 20379:2018 pdf free.Fine ceramics (advanced ceramics, advanced technical ceramics)
The setting of the shear rate shall be performed under the permitted conditions of the instrument.Based on the measurement programme, the shear rate is increased continuously or stepwise. In order to allow sufficient destruction of the aggregated or flocculated structure in the slurry during the increase in the shear rate, a maximum shear rate of 300 s-1 or more is recommended. However, this does not apply if it reaches the measurement limit in the case of high viscosity. When the measurement time of the increase and decrease of the shear rate is short, it is not possible to observe a sufficient hysteresis. In addition, if the measurement time is long, sedimentation may occur. Therefore, a measurement time of 90 s each is recommended for the increase and decrease operation of the shear rate. For the stepwise method, it is recommended that measurements of the increase or the decrease of the shear rate are performed at the shear rate as much as possible (10 stepwise).
After putting the slurry into the viscometer, enough time shall be allowed to reach the setting temperature for measurement. If the slurry has sedimentation property, it shall be rotated at a constant shear. rate until it reaches a constant temperature in order to prevent sedimentation. Under the conditions described in 8.1.1, the measurement of the flow curve shall be performed as a function of the increase of the shear rate. After reaching the maximum shear rate, the shear rate is stopped. After resting the measured slurry for 3 min to 5 min in order to recover the thixotropic properties of the slurry,the flow curve is measured again using the same procedure. The operations, i.e. the increase/decrease of the shear rate and the static state of the slurry, shall be carried out at least three times.
In order to minimize the influence of the flow curve due to particle sedimentation or drying out of the slurry, prompt measurement and sealing of the sample container are recommended.ISO 20379 pdf download.
