ASTM D2669 Standard Test Method for Apparent Viscosity of Petroleum Waxes Compounded with Additives (Hot Melts)
7. Procedure
7.1 Selection of Spindle - From the estimated viscosity of the sample and Table A1.1, select a spindle size and speed combination that preferably will produce readings within the range recommended by the manufacturer. Attach the spindle to the viscometer, with guard attached and mount the instrument on its stand.
NOTE 2 - Care must be taken while storing and handling the spindle. It should be protected from dust, corrosive deposits, and mechanical abuse. Avoid touching the calibrated section of the spindle with the hands. Thoroughly clean it and the guard after each use.
7.2 Preparation of Sample - In a suitable container, melt approximately 800 g representative of the sample to be tested on a hot plate or in an oven. Bring the temperature of the sample to 120 to 150°C (250 to 300°F) and stir to ensure homogeneity, taking care not to whip air into the melted sample. Fill the 800-ml test beaker with the melted sample to a level about 25 mm (1 in.) from the top. Place the filled beaker into the heating mantle which is supported by the laboratory jack in its lowered position. Connect the heating mantle to the autotransformer which, in turn, is connected to the proper ac supply. Connect the viscometer to its proper ac supply. Position the viscometer with spindle and guard attached, the stirrer, and thermometer as shown in Figs. A1.1 and A1.2. Mount the thermometer so that the center of its bulb is in the same horizontal plane as the center of the test section of the spindle, and spaced approximately the same distance as the guard from the spindle, about 13 mm (1/2 in.). Position the stirring propeller about midway between the bottom of the guard and the bottom of the beaker. Position the complete assembly so that the test portion of the spindle is spaced approximately 19 mm (3/4 in.) from the side of the beaker when the beaker containing the sample is in the operating position. Raise the beaker containing the sample by means of the laboratory jack so that the spindle is covered to about 6 mm (1/4 in.) below its immersion mark. Adjust the stirrer speed to give maximum agitation of the test sample without permitting vortex or air bubble inclusion. Apply heat to the sample by adjusting the autotransformer, and raise its temperature to about 5°C (10°F) above the highest test temperature. Maintain stirring throughout the heating cycle, being careful to prevent air entrainment in the sample.
NOTE 3 - As the temperature of the sample increases, its liquid level will approach the immersion mark on the spindle. Be careful to prevent the sample level from rising above the immersion mark on the spindle. Final immersion adjustment shall be made just before viscometer readings are determined.
7.3 Viscosity Determination - When the temperature of the sample reaches 5°C (10°F) above the highest test temperature, shut off the autotransformer, start the viscometer motor, and continue stirring. The temperature of the sample will begin to lower, and when it becomes 0.5°C (1°F) above the intended test temperature, stop the stirrer, but continue the spindle rotation. Wait 5 s, and readjust the viscometer to the immersion mark on the spindle. Allow the spindle to make three complete additional rotations. Engage the pointer clutch, and stop the viscometer motor when the pointer is in view. Record the dial reading. Restart the viscometer motor, release the clutch, make three additional spindle revolutions, engage the clutch, and stop the viscometer motor when the pointer is in view. Record the second dial reading, and repeat the above operation to obtain a total of three readings which should be completed within a period of about 1 min. During this time the temperature of the sample should fall no lower than 0.5°C (1°F) below the intended test temperature. Record the three test readings and the test temperature. Immediately after the final reading, start the stirrer motor and viscometer with the clutch engaged. Permit the temperature of the sample to drop about 15°C (25°F), and repeat the same procedure at a lower temperature. Continue this sequence to produce dial readings at four or more different temperatures, each spaced approximately 15°C (25°F) lower than the preceding test temperature.
NOTE 4 - The range of test temperatures shall include all temperatures at which apparent viscosity values are desired. Minor vertical adjustments of the spindle may be required to maintain its proper immersion as the volume of the sample decreases with lower temperatures.
8. Calculation
8.1 Determine the averages of the three scale readings made for each test temperature. Calculate the apparent viscosities, in pascal seconds or millipascal seconds, by multiplying the average viscometer scale reading for each test temperature by the factor indicated in Table A1.1 for the spindle and speed combination used.
8.2 Plot the apparent viscosity values obtained on the log scale, and the corresponding test temperatures on the linear scale of appropriate semilog paper. From the plot, determine the apparent viscosity of the sample at any temperature within the range of the test temperatures.
