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Brookfield Viscosity Measurement of Salt-Added Carbopol® Resin Adhesives

Abstract: Carbopol resin-based glue maintains high viscosity even with the addition of inorganic salts. This article mainly introduces how to measure the Brookfield viscosity of Carbopol resin-based glue after adding sodium chloride salt.

Safety protection work:

1. Wear safety goggles and gloves.

2. Resin dust should be avoided to irritate the respiratory tract.

3. If resin dust gets into the eyes, wash with 1% saline for 15 minutes. If normal saline is not available, rinse with plenty of clean water for 15 minutes, then seek medical attention.

4. Take care to protect clothing from contamination. Note: If the substance to be tested contains inorganic salts or other impurities, or the use of any glass utensils will affect the viscosity measurement results.

equipment:

1. Analytical balance with an accuracy of 0.002 grams.

2. Agitators with three impeller blades (see Appendix 1) and agitators with 3.25-inch "S" shaped paddles (see Appendix 2).

3. Brookfield constant temperature water bath.

4. Brookfield viscometer, model RVF, RVT, or RVTD, or other digital viscometer, with modified leg guards (see Special Note 1 for details on modification).

5. A set of RV spindles for Brookfield viscometers, made of 316 stainless steel.

6. Brookfield viscosity standard oil: 1000cP, 5000cP, 12500cP, 30000cP, 60000cP. The viscosity of the standard oil used in the calibration should be close to the viscosity range of the sample to be tested.

7. Griffin beaker, 800 or 1000ml capacity.

8. 500ml measuring cylinder.

9. Fisher Chain Clip #05-745.

10. thermometer.

11. Aluminum weighing pan.

12. pH meter.

13. Tannin Pyrex dish, 70x50mm.

14. dryer.

Reagents: (all reagents are provided by Fisher Technologies)

1. Sodium hydroxide pellets

2. Sodium chloride

3. Distilled or demineralized water

4. Phenolphthalein indicator: 1% dissolved in 60% formaldehyde solution

5. Bromomethyl blue indicator: 0.1% aqueous solution

6. pH Buffer: Used to calibrate pH meter Steps: *Part: Glue preparation NOTE: The Brookfield viscosity of Carbopol resin-based glues is sensitive to changes in shear, as well as changes in temperature and pH. These factors must be controlled in the measurement process.

1. Spread the sample evenly on an open aluminum or glass pan. Dry under a 29-inch mercury lamp at 176°F (or 80°C) for 1 hour.

2. The rotational speed of the three-blade impeller mixer was set at 1000±10 RPM.

3. Measure 500ml of distilled or mineral water with a graduated cylinder and pour it into an 800ml or 1000ml beaker.

4. Stir the beaker under the mixer, pay attention to the shaft of the mixer to insert at an angle of 60 degrees, and place it on one side of the beaker. Clamp the beaker with a chain clamp. The impeller stirring paddle should be as close to the bottom of the beaker as possible.

5. After drying the Carbopol resin, it was moved to a desiccator and cooled to room temperature.

6. After the temperature of the resin reached room temperature, 0.005 g was weighed into an aluminum pan with a balance. The correspondence between the weight of the dry resin and the concentration of the glue solution is as follows: 0.25 g - - - 0.05% solution 1.00 g - - - 0.2% solution 2.50 g - - - 0.5% solution 5.00 g - - - 1.0% solution 20.00 g - - - 4.0% solution

7. Turn on the mixer and carefully add the resin to the beaker. Addition time is 3/4 to 1/2 minute. Note: Carbopol resin will agglomerate on the surface of water if added too fast. This will result in insufficient dispersion and an incorrect viscosity measurement of the final glue. A metal sieve can be used to help pour the resin into the water.

8. When all of the Carbopol resin has been added, start the timer and mix at 1000 RPM for 15 minutes.

9. If required, add 5 drops of phenolphthalein indicator and 15 drops of bromomethyl blue indicator.

10. Move the dispersed solution to a water bath at 25±1°C for 30 minutes. Be careful to remove all bubbles.

11. Adjust the glue with 18% NaOH. The corresponding relationship between the amount added and the concentration of the glue is as follows:

0.4ml - - - 0.05% glue

1.8ml - - - 0.2% glue

5.4ml - - - 0.5% glue

11.3ml - - - 1.0% glue

40.5ml - - - 4.0% glue

12. Install the "S"-shaped stirring paddle, and adjust the speed of the blender to 300±25RPM. When the stirring is stopped, adjust the depth of the stirring paddle so that it is just immersed under the liquid surface, so that the air is easier to discharge the glue. Turn on the power switch of the blender , stir for 2 minutes, move the beaker up and down while stirring, and be careful not to introduce air.

13. Check the pH of the glue with a pH meter. If the pH value is lower than 7.3, add 18% NaOH solution and stir. The pH range should be between 7.3 – 7.8. If the pH is higher than 7.8, discard the sample and remake the glue.

14. Put the pressed glue in a water bath at 25±1℃ for 1 hour. Note: The measurement of viscosity should be carried out after 60 to 75 minutes of constant temperature to avoid slight changes in viscosity with time.

15. The viscosity of the glue was measured with a Brookfield RV viscometer at 20 RPM.

16. a) For Brookfield RVF and RVT type viscometers, take readings at 3, 6 and 9 RPM and record the average of these readings. The range of these three readings must not exceed 0.5 scale units of the 100 unit scale.

b) For Brookfield's RVTD type viscometer, read the maximum data in 30-45 seconds. NOTE: All viscometer readings must be above 10 and below 90. If the reading is outside the 10-90 scale, select another rotor for measurement. (Choose those rotors that give the largest readings for the most accurate results.)

Calculation: Viscosity (cPs) The dial reading constants for different spindles are as follows: Spindle Constant 3 50 4 100 5 200 6 500 7 2000 Part II: Adding Salt

1. First prepare the glue to be tested, its concentration is 0.2%, 0.5%, 1.0%.

2. After reading the viscosity of the glue, add an appropriate amount of salt and weigh it with an aluminum weighing pan. Salt Content Weight 0.2% 1.0g 0.5% 2.5g 1.0% 5.0g

3. Mix the glue and salt well with an "S" shaped paddle at low speed. The mixing process is completed within 30-60 seconds.

4. Put the glue back in a constant temperature water bath at 25±2℃ for 30 minutes.

5. Measure the viscosity of the glue with a Brookfield RVF, RVT or RVTD type viscometer at 20 RPM.

a) For Brookfield RVF and RVT type viscometers, take readings at 3, 6 and 9 RPM and record the average of these readings. Note that the range of these three readings must not exceed 0.5 units of the 100 unit scale.

b) For Brookfield's RVTD type viscometer, read the maximum data in 30-45 seconds.

Special Instructions:

1. Modified Legging Dimensions: When measuring from the bottom of the viscometer body to the bottom of the leggings, cut the length of the leggings to 7 3/4 inches long. Without this modification, the #7 rotor would not be immersed to the proper depth when using a 1000ml beaker.

Note: The dial reading of the viscometer must be above 10 and below 90. If the reading is outside the 10-90 scale, select another rotor for measurement.