In plastic gravure printing, how to control the ink printing viscosity is a very critical issue. Especially in high-speed rotogravure printing, whether the printing viscosity of temperature-varying ink is properly controlled is directly related to most quality problems such as pigment transfer, dirty plates, gloss and brightness of printed products, pigment adhesion fastness, and static electricity. Affect the yield of printed products and work efficiency. Then, in plastic gravure printing, how to control the printing viscosity of ink can take into account many aspects to ensure the quality of printing. This requires us to first understand the two concepts of ink printing viscosity and viscosity. According to the relevant teaching materials or materials, the overview of the relationship between the two is usually very vague, and some even regard the two as a concept. In fact, there are obvious differences between the two. The following summarizes the points to explain the printing viscosity of ink Difference and connection with stickiness.
1. The definition of temperature change ink is different
If the flow rate of each layer of the ink is different due to some external reasons, especially there are acting forces and reaction forces between the two liquid layers with different flow speeds at the contact surface. This pair of forces is called the internal friction of the ink, which shows The property is called the viscosity of the ink. The physical quantity that measures the viscosity of ink is called viscosity.
2. Differences in the performance of temperature change inks
Viscosity occurs when resisting ink film separation, and the fluid only exhibits viscosity when flowing, and does not exhibit viscosity in stationary fluids. The effect of viscosity is to block the relative sliding inside the fluid, thereby blocking the flow of the fluid, but this blocking effect can only delay the process of relative sliding but not stop it. This is an important characteristic of fluid viscosity, and it is a rheological parameter that represents the internal adhesive properties of the fluid. Viscosity is a measure of the internal friction generated between molecules when a liquid is moved by an external force. Viscosity is a property of fluids, whether it is stationary or flowing, it will always exist.
3. Different detection methods and units of temperature change ink
Viscosity is measured with a rotary viscometer. Use a viscometer to measure the resistance caused by the separation of the ink or the film layer of the connecting material, and the number is the viscosity value. There is no unit for stickiness.
There are various methods for measuring viscosity. Generally, there are capillary viscometer, small-hole viscometer, rotary viscometer and rotary cone-plate viscometer. Generally, a rotary viscometer is used to measure the viscosity of ink. When the rotor is subjected to the viscous resistance of the liquid, the balance spring generates torque, which counteracts the viscous resistance and finally reaches equilibrium. At this time, the pointer connected to the balance spring indicates a certain reading (that is, the torsion angle of the balance spring) on ​​the scale disc. Multiply the reading by a specific factor to get the viscosity of the liquid. This shows that the viscosity and viscosity are different in units.
4. Different factors
The factors that affect the viscosity are: the diameter, hardness and elastic modulus of the elastic roller, the nature of the roller, the rotation speed of the roller, the temperature of the roller, the ambient temperature and humidity, the temperature of the sample, the thickness of the ink film, the ink or the bonding material, etc. Influence, the condition of the elastic roller during the cleaning process, the nature of the test sample, etc.
The factors that affect viscosity are: viscosity is closely related to its temperature, concentration of component particles, particle size, etc., and has little relationship with humidity and air pressure. The measurement accuracy and measurement unit of different measurement methods are different and cannot be converted to each other.
From the above four points, we can see that there is a big difference between ink printing viscosity and viscosity, but the two are still related. The main performance is that the viscosity is a physical quantity that measures the viscosity of the fluid. The dynamic viscosity of the fluid is determined by the inherent physical properties of the fluid. Its value is a direct measure of the viscosity of the fluid. It is also the resistance of the fluid to shear deformation in motion. A measure of ability. Under the same environmental conditions, a large viscosity means a high viscosity and vice versa.
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