How do plasticizers affect the adhesion of inks on PVC?
With a new round of experimental proofs, this time we will add 2 parts of transparent additives to 1 part of the original printing ink. At this point the pigmented printing ink is only 33% of the total and it can be found that the printability of this mixture has been further optimized and the colors are still within the accepted range for most manufacturers’ products. When configuring printing inks, it is necessary to test different brands of printing inks, because there are many printing inks that are diluted in color when mixed with 50% additives, while some do not undergo any changes. The additives and plasticizers used by manufacturers to formulate printing inks are the most important factors that cause differences in the quality of printing inks, with plasticizers being the most important ingredient, also called reducers in most cases.
Mixing the right amount of printing ink with the right amount of reducing agent will make the ink less viscous, thereby improving the printability of the printing ink. Usually in the four-color printing does not need to add reducing agent, and in the screen printing process, the formation of printing ink dots is determined by the size of the screen mesh. If the mesh leaves the surface of the substrate, it will lead to the distortion of the ink dot, and the printed image will become blurred. The reducing agent in the container is as clear and transparent as water, if you scoop up a spoonful, it will feel a bit like clear oil, and the manufacturer’s instructions should be strictly followed when using it. If you add too much reducing agent, it will be difficult for the printing ink to combine with the textile no matter how much drying agent you add, how slow the printing speed is, and how long it takes to pass through the drying agent. So you must be careful when adding reducing agents.
Plasticizers are chemicals that make printed materials more flexible and supple, and their use in PVC (polyvinyl chloride) is very common. The type and amount of plasticizer added to flexible PVC or other plastics depends largely on the mechanical, thermal and electrical properties one requires from the printed material. Plasticizers have the potential to migrate to the surface of the substrate and affect the adhesion of the ink. Plasticizers left on the surface of the substrate are a kind of contamination, which will reduce the surface energy of the substrate. The more contamination on the surface, the lower the surface energy, and the less it will adhere to the ink. To avoid this, one can clean substrates with a mild cleaning solvent before printing to improve their printability.
2. How many lights do I need to use for curing?
Although ink systems and substrate types vary, in general, a single lamp curing system is sufficient. Of course, if you have enough budget, you can also choose a two-lamp curing unit to increase the curing speed. What makes two curing lamps better than one is that a dual lamp system provides more energy to the substrate at the same transfer speed and parameter settings. One issue we need to focus on is whether the curing unit can be sufficient to dry the ink printed at normal speeds.
3. How does the viscosity of the ink affect the printability?
Most inks are thixotropic, which means that their viscosity changes with shear, time and temperature. In addition, the higher the shear rate, the lower the viscosity of the ink will be; the higher the ambient temperature, the lower the annual ink will be. Screen printing inks generally achieve good results on the press, but occasionally have problems with printability depending on press settings and pre-press adjustments. Also the viscosity of the ink on the press is different from the viscosity it has in the cartridge. Ink manufacturers will set a specific viscosity range for their products. For inks that are too thin or too low in viscosity, the user can also add a thickening agent as appropriate, while for inks that are too thick or too high in viscosity, the user can also add a thinner.
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