This standard specifies the method for determining the viscosity of vulcanized natural rubber latex. This standard applies to vulcanized latex prepared from concentrated natural rubber latex. This standard also applies to the determination of the viscosity of natural rubber latex. GB/T 14797.2-1993 Determination of the viscosity of concentrated natural rubber latex and vulcanized latex GB/T14797.2-1993 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Determination of viscosity of vulcanized latex
Concentrated natural rubber latex
Natural rubber latex concentrate-Prevulcanized rubber latex-
Determination of viscosity
This standard adopts ISO1652-1985 "Latex-Determination of viscosity". Subject content and scope of application
This standard specifies the method for determining the viscosity of vulcanized natural rubber latex. This standard is applicable to vulcanized latex prepared from concentrated natural latex. This standard is also applicable to the determination of the viscosity of natural latex. 2 Reference standards
L Sampling
GB8290 Natural concentrated latex
GB8292 Determination of total solid content of natural concentrated latex 3 Test principle
GB/T 14797. 2 --93
3.1 When the rotor immersed in latex to a specified depth rotates at a constant low speed and strong torque driven by a synchronous motor, the resistance of the latex to the rotor will generate a torque. When the torque of the rotor and the hairspring in the machine reach a balance, the magnitude of the hairspring torsion angle indicated by the pointer is as follows:
Qk··n
From the above formula, we get =
In the formula: Q—haisspring torsion angle:
Table 1—calculation constant, which is related to the hairspring rigidity coefficient, the radius and length of the rotor; ~ angular velocity; bzxz.net
7—viscosity.
Calculate the viscosity of the object from the obtained hairspring torsion angle and angular velocity. 4 Instruments
4.1 Viscometer
The viscometer is driven by a special synchronous motor through gears and couplings to drive the rotor, and the required speed is adjusted by changing the gears. The viscometer is equipped with different rotors, and the sizes of the rotors are shown in Table 1. Different measuring ranges can be obtained by selecting different rotors and speeds. The models of the viscometer are NDJ-1 in China and LVT or LVF abroad, for reference. The speed of the viscometer is selected to be 60r/min.
Approved by the State Technical Supervision Week on December 25, 1993
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Implemented on August 1, 1994
The smallest rotor that can measure the viscosity should be used. The rotor should be precision machined as shown in the figure below.
Rotor number
GB/T 14797.2-93
Table 1 Rotor size
4.2 Beaker: inner diameter greater than 85mm, capacity 600mL. c
4.3 Water bath constant temperature: enables the sample to be measured at a temperature of 35±2℃. 5 Sample preparation
5.1 Sampling Take samples according to the method specified in GB8290. 5.2 Determine the total solid content of the sample according to the method specified in GB8292. D
5.3 Prepare a sample with a total solid content of 55±0.5% by diluting with distilled water, weighing more than 600g, and gently stir the sample for 5min, taking care to avoid mixing with air.
6 Operation steps
6.1 Adjust the bubble level on the viscometer housing so that the rotor on the motor shaft is vertical to the ground, install the U-shaped steel bar protection device, connect the selected rotor, and set the speed to 60r/min. 6.2 Filter the prepared sample into a 600mL beaker using a stainless steel mesh with a nominal aperture of about 500um, and be careful not to bring in air. If there are bubbles, leave it to stand and remove them. Place the beaker in water to maintain a constant temperature, and stir it gently from time to time to make the temperature uniform. Use a thermometer to measure its temperature to 35±2℃ and record the precise temperature. 6.3 Carefully insert the protective device and rotor into the sample (prevent bubbles from being entrained during the whole process) until the surface of the latex submerges the middle scale of the groove mark on the rotor, and adjust the rotor to be placed vertically in the middle of the beaker. If there is a crust on the surface of the latex, it should be removed with a medicine spoon first. 6.4 Start the motor of the viscometer according to the viscometer operating instructions, and read the scale indicated by the instrument after 20~~30s of equilibrium. 7 Expression of test results
Use the corresponding rotor factor listed in Table 2 multiplied by the scale reading to calculate the viscosity of the latex, the unit is mPa·s142
Subtract the rotor factor
It is also acceptable
8 Test report
Rotor number
The test report should include the following items: (1) Model of instrument used;
(2) Rotor number used;
(3) Rotor speed during measurement;
(4) Total solid content of the test sample;
(5) Exact temperature of the latex during measurement;
(6) Measurement results.
GB/T 14797.2—93
Rotor factor of viscometer
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Relative density
(25/25℃)
GB/T 14797.2—93
Appendix A
Relative density and absolute viscosity of glycerol aqueous solution (supplement)
%(m/m)
Corrective
mPa·s
GB/T14797.2—93
Appendix B
Viscometer calibration method
(reference)
Purchase analytical pure glycerol, dilute with double distilled water to 82% (m/m) and 70% (m/m) solutions, 600g of glycerol aqueous solution, place at a constant temperature of 25℃, and measure its relative density with a liquid relative density balance. And use the data in Appendix B to make a relative density-glycerol content curve and a glycerol content-viscosity curve. Then find out the accurate glycerol content from the relative density-glycerol content curve, and then find out the absolute viscosity from the glycerol content viscosity curve.
Additional Notes:
This standard is proposed by the Ministry of Agriculture of the People's Republic of China. This standard is under the jurisdiction of the Natural Rubber Standardization Technical Committee of the National Technical Committee for Rubber and Rubber Products Standardization. This standard was drafted by the South China Tropical Crops Product Processing and Design Institute. The main drafters of this standard are Zheng Shugui, Shen Rong and Zhang Beilong. 145
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