What is screen printing ink thixotropy?

Thixotropy is the ability of a liquid to lose its viscosity due to stress and then return to its original viscosity. In the screen printing process, it is a reversible phenomenon that the ink becomes thicker after standing still for a certain period of time, the viscosity becomes larger, and becomes thinner after stirring, and the viscosity becomes smaller. Because the shape of the pigment particles in the ink is irregular, even though a layer of linking material is absorbed, it is also an irregular ball. Therefore, after standing still for a certain period of time, the pigment particles will contact or be very close to each other, causing mutual attraction, hindering the free movement of the particles, and the ink will become thicker and viscous. However, after this temporarily stable structure is stirred by external forces, It is quickly destroyed, the mutual attraction between the particles is lifted, the free movement of the particles is restored, the fluidity is improved, the ink becomes thinner, and the viscosity decreases.

The smaller the thixotropy of screen printing ink, the better. In order to eliminate this unfavorable factor, before printing, the ink should be fully stirred to return to normal state, and then printed.

The more irregular the pigment particles in the ink, the more porous (such as black ink), the greater the thixotropy. On the contrary, such as yellow ink, the smaller the thixotropy. There are more linking materials in the ink, less pigments, and the thixotropy is also small, and vice versa. Large thixotropy. In addition, the difference of linking materials also has a great influence on thixotropy. For example, oil plastic made of polymerized vegetable oil has small thixotropy, and polymer resin as linking material has large thixotropy.