This method is suitable for the determination of the viscosity of transparent liquids such as paints, resin solutions and varnishes. The bubble viscometer is composed of a group of glass tubes of the same specification sealed with colorless and transparent mineral oils of different viscosities . Standards arranged in ascending order. Its characteristic is that it can give accurate viscosity data in a short time , so it is often used in the middle control of the coating production process. Due to the different specifications of the bubble viscometer, there are the gash tube method and the ASTM tube method, and the gash tube method is mainly introduced below.
This method was originally provided by the Gardner Laboratory in the United States, and it is called Gardner-Holdt (Gardner-Holdt) bubble viscometer, so it is customary to call it a Gardner bubble viscometer or a Grignard tube.
Instruments and Materials
(1) The inner diameter of the glass tube of the Gardner Bubble Viscometer is (10. 75 ± 0. 025) mm, the total length is (114 ± 1) mm, and a line is drawn at 99 mm and 107 mm from the bottom of the tube , in English letters Numbering, the viscosity ranges from the smallest A-5 to the largest Z-10, a total of 41 grades, their known viscosity range is 0. 005-1066cm²/s, see Figure 1-17.
(2) The inner diameter of the tube is (10.75 ± 0.025) mm, the total length is (114 ± l) mm, and a line is drawn at 99 mm and 107 mm from the bottom of the tube to ensure that the liquid height is 99 mm and the bubble height is 8 mm.
(3) constant temperature Water Bath.
(4) Corks.
(5) The test tube rack is a metal rack with plastic handles, and standard tubes and samples can be placed in parallel in a completely vertical position.
(6) STOPWATCH.
test methods
(1) Contrast method
①Put the sample to be tested into a Grignard tube of the same specification, and adjust the temperature to (25±0.5)"C with a constant temperature Water Bath.
②Choose four standard tubes with a viscosity close to that of the sample, and insert the plus tubes into the test tube rack together, as shown in . Leave a specified space above the sample, cover with a cork, and place four glass tubes marked with letters and a grid containing the sample.
③ During the test, reverse the test tube rack, the sample flows down due to its own gravity, and the air bubbles rise to the bottom of the tube, compare the moving speed of the air bubbles find a standard tube that is closer to the bubble rise time of the sample, as shown in Figure 1-19 shown.
(2) Timing method
Put the sample to be tested into the Grignard tube, cover with a cork, adjust the temperature to (25±0.5 )"C in a constant temperature Water Bath, quickly turn the Grignard tube vertically after taking it out, and start the stopwatch at the same time to record the rise of the bubbles time.
4 results show
(1) The comparative method is represented by the letter number of the same or the closest standard tube.
(2) Timing method The time for bubbles to rise is the viscosity of the sample, expressed in seconds (s).
Note: When using this method, it should be noted that when holding the sample, the size of the tube and the size of the standard tube, the size of the bubble and the test temperature (generally 25°C) should be exactly the same.
