Printing ink of steel barrel wire in different environments (III)
8 Light resistance of ink
the light resistance of steel barrel wire printing ink is the intensity of light resistance of the ink. Ink fading is caused by the absorption of light energy by pigment molecules. The Lightfastness of the ink mainly depends on the Lightfastness of the pigment or dye. The Lightfastness of the printed text on the surface of the steel barrel depends on the Lightfastness of the pigment, the material of the steel barrel, the thickness of the ink layer, the connecting material and the consistency of the ink.
9. Chemical resistance of ink
the ability of steel barrel wire printing ink to resist water, acid, alkali and solvents is collectively referred to as chemical resistance. According to the actual application, the commonly used determination standards and methods include soaking method and wet rubbing method. Soaking method is to soak the steel drum after printing and drying in the selected water, acid, alkali and solvent, take it out after a certain time, and compare the change degree of the steel drum before and after soaking the printed pictures and texts; Wet wiping method is to wet the cloth with the selected solution, wet wipe it back and forth on the steel drum after printing and drying for several times, and then compare the differences before and after wet wiping of the pictures and texts printed in the steel drum.
II. Adhesion of steel barrel wire printing ink
steel barrel wire printing requires good adhesion of ink, and the adhesion of silk printing ink is also the most prominent problem of ink after steel barrel wire printing. If the ink does not have adhesion on the steel drum after printing, it is equivalent to no printing, which will also cause great waste. The adhesion of ink involves the adhesion mechanism between ink and steel barrel. At present, it is generally believed that the reason for affecting the adhesion of ink is that Jinan testing machine is strong? The following points:
1 Resin is the main component of ink binder, and the adhesion of ink is closely related to the performance of resin.
① molecular weight. If the molecular weight of the resin is too close to that of the coating on the surface of the steel barrel, the ink solvent is not easy to choose. If the molecular weight of the resin is too large, in order to make the ink reach the required viscosity of silk printing, the solid (resin) content in the ink is too small, resulting in the waste of solvent. With high molecular weight and high melting point, it is difficult to dissolve in solvent. Some precautions in the operation of waterproof roll tensile testing machine are unfavorable to the adhesion effect. If the molecular weight of the resin is too small, the cohesion compatibility is poor, and the adhesion effect is poor. The molecular weight selection of inking resin is very important and must be appropriate. ② glass transition temperature. Only when the motion of polymer segments is above the glass transition temperature, there is a significant diffusion rate. The whole chain movement can only be carried out at high temperature. For room temperature curing inks, the glass transition temperature of the resin should be very low, which is obviously beneficial to adhesion. ③ resin components. The functional groups in resin molecules and five gold tool torque detection equipment are used for the change strength test of all kinds of wrenches, as well as the torsion strength test of all kinds of parts and wrenches The torsional test of parts and components can also be carried out by adding corresponding accessories The chain structure directly affects the adhesion effect of the ink on the steel barrel. Therefore, the printing ink used for steel barrels with different coatings in steel barrel wire printing is also different. For example, the coating on the surface of the steel barrel includes amino baking paint coating, zinc coating, chromium coating and tin coating. ④ element content of resin monomer. The change of some element content in synthetic resin monomer will change the performance of the resin. Therefore, when designing the formula of steel drum screen printing ink, synthesizing some special resins will greatly improve the performance of the ink. A change in the content of an element in the resin monomer will lead to a prominent change in a certain characteristic of the resin. ⑤ polarity and crystallinity of resin. The existence of polarity is conducive to the adhesion effect of ink, but the high polarity linear polymer has high crystallinity. Copolymerization and grafting can be used to modify the resin to destroy the crystallinity and maintain the polarity. (to be continued)
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