Knowledge of ink viscosity

Viscosity

Viscosity is the internal friction of a liquid. When the lubricating oil is relatively moved by an external force, the resistance generated by the oil molecules prevents the smooth flow of the lubricating oil. The magnitude of the resistance is called the viscosity. It is the main technical indicator of the flow properties of lubricants. The vast majority of lubricants are classified according to their viscosity. Therefore, viscosity is the main basis for the selection of various mechanical equipment.

The viscosity measurement method is divided into two major categories, absolute viscosity and relative viscosity. Absolute viscosity is divided into two kinds of dynamic viscosity and kinematic viscosity; the relative viscosity of the Enzi's viscosity, viscosity and Reye's viscosity and other representations.

1. Dynamic viscosity η

In the fluid, the resistance generated when the two areas are each 1 m2, 1 m apart, and the relative moving speed is 1 m/s is called dynamic viscosity. The unit Pa.s (Pa.s.). The kinematic viscosity units used in the past are either poise or centipoise. Poise or centipoise is a non-statistical unit of measure.
1Pa.s=1N.s/m2=10P poise=10 3rd power cp=1 Kcps
The ASTM D445 standard specifies the use of kinematic viscosity to calculate the dynamic viscosity, that is, η=ρ.
Η-dynamic viscosity, Pa.s ρ-density, kg/m3; υ-kinematic viscosity, m2/s
China's national standard GB/T506-82 is a method for measuring the low-temperature dynamic viscosity of lubricating oils. This method is used to determine the low temperature (0～-60°C) dynamic viscosity of lubricating oil and dark petroleum products. Under the strict control of temperature and different pressure conditions, the time required to measure the volume of a sample in a calibrated constant capillary viscometer flows in seconds. The dynamic viscosity is calculated in units of Pa.s from the time the sample passes through the capillary and the product of the capillary calibration constant and the average pressure. The difference between the repeated determination of the two results of this method should not exceed ± 5% of its arithmetic mean.

2, kinematic viscosity

The ratio of the dynamic viscosity of the fluid, η, to the density, ρ, of the fluid at the same temperature is called the kinematic viscosity. It is a measure of the flow resistance of this fluid under gravity. In the International System of Units (SI), the unit of kinematic viscosity is m2/s. In the past, cSt was usually used as the unit of kinematic viscosity, which was equal to 10-6 m 2 /s, (ie, 1 cSt = 1 mm 2 /s.

The kinematic viscosity is usually measured with a capillary viscometer. Under strict temperature and reproducible driving pressure head, it is time to measure the volume of liquid flowing through the calibrated capillary viscometer under the action of gravity. In order to measure the kinematic viscosity, the temperature of the fluid to be measured must first be controlled and the temperature measured. Accuracy requirements to reach 0.01 °C; Second, the size of the appropriate capillary must be selected to ensure that the outflow time can not be too long nor too short, that is, thicker capillary tubes for viscous liquids, thinner capillary tubes for thinner liquids, flow time should be Not less than 200 seconds; the viscosity tube constant must be calibrated regularly; and the viscosity tube must be vertical when installed. National standard for kinematic viscosity is GB/T256-88, equivalent to ASTM D445-96/IP71/75.

3, the viscosity of 0E

China's national standard for the determination of petroleum products Nen's viscosity GB/T266-88.
This is a relative viscosity commonly used in the past. It is defined as the time (s) required for a 200-ml liquid to flow through an Enzi's viscometer at the specified temperature, and the same volume of distilled water is required to flow through the Enzi's viscometer at 20°C. The ratio of time (s) is called the Engel's viscosity.

4, Redwood's viscosity (Redwood)

This viscosity is mainly used in the United Kingdom and Japan. It is defined as the time in seconds required for a 50 ml test run at a specified temperature of 60°C or 98.9°C through a Rayleigh viscometer.

5. Saybolt Universal Viscosity

In the United States, this unit of viscosity is commonly used. It is defined as the time in seconds required for a liquid to flow out of 60 ml of liquid at a specified temperature from a Saybolt viscometer. The American standard method is ASTM D88.
6, several kinds of viscosity conversion
1) Conversion of Kinematic viscosity and Kinematic Viscosity Kinematic viscosity Ï…(mm2/s)=7.310E-6.31/0E
2)Reynolds viscosity and kinematic viscosity conversion Kinematic viscosity Ï…(mm2/s)=0.26R-172/R When R>225s, use Ï…(mm2/s)=0.26R
3) Conversion of viscosity and kinematic viscosity:
Kinematic viscosity Ï… (mm2/s) = 0.225S When S > 285s