ASTM D4287 test method for high-shear viscosity using a cone/plate viscometer
5. Apparatus
5.1 Cone/Plate Type Viscometer, with cone/speed combination producing a rate of shear of 12 000 s(-1). The viscometer must provide a viscosity measurement rage of either 0 to 10 (P) or 0 to 5- (P. With higher viscosity materials, other cones and speeds may be used upon agreement between the producer and the user, but it should be noted that these may give lower shear rates not truly representative of application conditions. Refer to Fig. 1 and Fig. 2 of an analog and digital cone and plate viscometer.
NOTE 1 - The SI units for viscosity are pascal-seconds (Pa•s = 10 P, 1 mPa•s = 1 cP).
6. Reagents and Materials
6.1 Water or Solvent - The viscometer should be zeroed according to the manufacturer's specification. Zeroing procedures that require liquid may be satisfied with water or a low viscosity solvent such as xylene or mineral spirits.
6.2 Mineral Oils - Three standard mineral oils with known viscosities (certified by an approved laboratory) lying between 10 and 90 % of full scale to be used for calibrating the instrument.
NOTE 2 - Silicone oils should be avoided because of their tendency to contaminate instruments, containers and other equipment and because of the possibility of shear thinning behavior at high shear rates.
7. Sampling
7.1 Take a representative sample of the product to be tested in accordance with Practice D3925. If the sample has a tendency to settle or separate on standing, it must be stirred or shaken until homogeneous before a test specimen is taken from it. The specimen must be free of any foreign matter or air bubbles and its volume must be sufficient to cover the portion of the viscometer plate under the cone when the latter is brought into contact with the plate.
8. Preparation of Apparatus
8.1 The viscometer should be zeroed on a daily basis when in regular use, or otherwise before use, according to the viscometer operating manual. With the analog-type viscometer, if the pointer does not indicate zero, it may be adjusted by means of a lever on the left-hand side of the upper part of the instrument housing. If the instrument cannot be zeroed, adjustment should take place according to the manufacturer's suggestions.
8.2 Verify the calibration of the apparatus by following the procedure in Section 9, but using standard refined mineral oils having Newtonian characteristics and known viscosities. If the viscometer reads the correct viscosity (or within 5 % of that value) with two or more oils whose viscosities bracket those of specimens to be tested, then the viscometer readings may be used as is. If the viscometer readings do not give the correct viscosities for the oils, then a calibration curve must be constructed by taking viscometer readings for three oils and plotting measured viscosity versus specified (correct) viscosity for the oils. Subsequent measurements are corrected to true viscosities through use of the curve.
8.3 Check the cones periodically for wear. Replace any cone that shows a definite flattening of the apex. Some users have found it necessary to replace cones every year. Others have had to do so more often when abrasive paints or pastes were being tested.
8.4 The determination must be made at a closely controlled temperature of 25 more or less 0.3°C , unless otherwise agreed. In order to check the temperature control, carry out the test as outlined in 9.1 with the standard refined mineral oil of the highest viscosity. Allow the viscometer to run with this oil for 5 min and determine whether the reading decreases. If the decrease is more than 10 %, the apparatus is unsuitable for the determination of viscosities at high rates of shear in accordance with this test method.
NOTE 3 - Many multitemperature cone/plate viscometers have heating, but not cooling, capabilities. Therefore, runs with these viscometers at 25°C should only be done at room temperatures at or below 22°C to ensure that the plate temperature does not go above 25°C.
