ASTM D1986 Method for Determining the Apparent Viscosity of Polyethylene Wax
7. Procedure
7.1 Use spindle number 31 for this test.
7.2 Preparation of Sample - Place 8 g or approximately 10 mL of sample in the sample chamber. Melt the sample in the thermo-container preheated and set at 140°C. If polyethylene wax has a melt point higher than 135°C, the procedure should be run at 150°C. Heat for 15 min with insulating cap on sample chamber. Avoid excessive or prolonged heating of the sample to minimize thermal and oxidative effects.
7.3 System Alignment and Spindle Insertion - With the viscometer raised, connect the spindle to the coupling nut (note left-hand thread). Lower the leveled viscometer and insert the spindle in the sample chamber until the tips of the alignment bracket is 2 mm (1/16 in.) above the top of the thermo container and in contact with the back of the locating ring. Place insulating cap over the sample chamber.
7.4 Turn on viscometer at the lowest RPM setting. When temperature equilibrium is indicated, turn off viscometer, remove the cap, raise the viscometer and spindle and inspect the liquid level on the spindle shaft. The liquid should extend about 0.6 to 1.3 cm (1/4 to 1/2 in.) up the spindle shaft. If the liquid level varies significantly from this, add or remove sample.
7.5 Lower viscometer and spindle and turn it on at the lowest RPM setting and wait for the temperatures to reach equilibrium. After equilibrium is reached, select a spindle speed (RPM), that will produce a scale reading nearest the midpoint of the scale between 10 to 95 unit range. Allow the spindle to rotate at this speed for 15 min before engaging the pointer clutch and stopping the motor to record the scale readings. Restart the motor, and allow at least five additional revolutions before taking a reading. Repeat this operation until three consecutive readings differ by no more than 0.5 units.
8. Calculations
8.1 Convert the average of these three readings to millipascal seconds, by multiplying this value by the appropriate factor taken from instrument instruction manual.
