Under the five key factors of the adhesion fastnes

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Five key factors for the adhesion fastness of printing ink (Part 2)

Second, the influence of solvent in ink binder. In the process of ink production and preparation, solvent will also affect the adhesion effect. We know that the solubility parameters of the resin and solvent used are similar, which should also be considered at the same time. However, the export, domestic demand and investment of the three carriages lie together. For plastic printing ink, we need to consider other printing effects as a whole

● the solubility parameters of resin and solvent are similar, which is conducive to dissolution

● the solubility parameters of plastics and plasticizers are similar, which is conducive to increasing plasticity

● the solubility parameters of ink solvent and plastic are similar, which is beneficial to the adhesion effect. However, it is necessary to prevent the plastic surface from being eroded too much by ink solvent. Precautions for using mortar tensile testing machine (even causing plastic deformation)

● the adhesion effect decreases when too many solvents with high boiling points are used

● improper solvent selection and poor adhesion effect. The use of solvents should be considered from many factors, so more than three mixed solvents should be used for printing ink solvents

● the solvent and binder (high molecular polymer) in the ink contact with the substrate to dissolve and dissolve the surface of the substrate, so that the substrate and binder in the ink diffuse each other, forming a borderless intermediate layer after mixing, resulting in the disappearance of the interface and the formation of a solid combination of oil and ink and substrate

III. Influence of additives in ink

there are many kinds of additives in ink, which mainly play a role in improving the performance of ink. The additives that play a role in the adhesion effect are as follows:

crosslinking agent: crosslinking agent can not only improve the adhesion effect of ink, but also greatly improve the hardness, solvent resistance, water resistance and drying speed of ink

coupling agent: the coupling agent promotes the coupling effect of resin and polymer substrate in the ink, which can improve the adhesion effect of the ink

plasticizer: plasticizer can improve the softness of the ink film and is also beneficial to the adhesion effect

IV. influence of ink performance

printing ink has good wettability, which is beneficial to the adhesion effect. If the substrate has not been soaked, and the ink has been dried or cured, the adhesion effect is poor, which involves the fluidity of the ink. Fluidity is also closely related to other factors of plate printing. Here we only discuss the adhesion of ink

● the volatilization rate of the solvent must be controlled in the preparation of ink, and the presence of high boiling point solvent is conducive to leveling

● use resin with appropriate molecular weight to prepare ink. The higher the viscosity of the resin, the worse the ink leveling

● add an appropriate amount of leveling agent to the printing ink

v. influence of substrate on adhesion fastness in the printing process

the material of substrate in plate printing directly affects the adhesion effect of ink. Preparing special inks for different substrates is a good way to overcome this effect. There are usually plastic inks, paper inks, fabric inks, wood inks, metal inks, leather inks, printed circuit board inks, ceramics, glass inks, etc. For different substrate materials, choose the appropriate ink, and through the change of the performance of the substrate, surface treatment and other means, you can also improve the adhesion fastness of the ink on the substrate

● when printing the substrate, it is very important to strictly degrease the substrate and check it before printing. When the surface of the substrate is attached with grease, adhesives, dust, etc., it will cause the ink to bond with the substrate not firmly. Inadequate surface treatment of plastic products before printing will also cause the problem of weak ink adhesion. Therefore, cleaning the surface of the plate printing substrate can also improve the adhesion fastness of the ink on it, and the existence of dust, grease and dirt on the substrate makes it difficult for the ink to adhere, so it must be removed

● the printing material is polyethylene film. In order to improve the adhesion with ink during printing, the surface must be flame treated; If it is a metal material, it must be degreased and dedusted before it can be printed. Because the metal cannot absorb the ink film after printing, it can only be dried by oxidation, evaporation and drying according to the temperature required by the ink. If the drying is not handled properly, the ink film will fall off. In addition, in order to make textiles waterproof in textile printing, silicon processing is generally required to ensure good ink adhesion fastness during printing

● oxidizing the surface of the substrate and changing the surface state of the substrate will greatly improve the adhesion effect of the ink. Usually, for substrates that are difficult to print, such as olefins, they can be printed smoothly after concept testing, chemical treatment, flame treatment, electronic shock and other treatments, mainly from platform molds to full-size prototypes

● objects such as glass and ceramics need high-temperature barbecue after printing, so as long as the temperature treatment is appropriate, the adhesion of the ink layer will be good. A simple way to test the adhesion fastness of ink film: glass and ceramic prints are exposed to rain and dew to see whether the ink is easy to peel off and fade. When the printed substrate is paper, to test the ink fastness, you can bend the printing surface repeatedly to see whether the ink layer at the crease is stripped. If the ink is stripped, the ink adhesion fastness is poor, otherwise it is strong

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