Printing Treatment Of Plastic Film
Treatment method Although non-polar polymers such as polyethylene and polypropylene have poor affinity for ink, satisfactory printing effects can still be obtained after proper treatment. Therefore, necessary treatment of plastic film before printing is a key step to ensure the quality of printed materials. To improve the printing effect, appropriate surface treatment, such as corona, flame or acid treatment, must be carried out, which can increase the polarity of the film and improve its printing performance. The treatment method usually involves increasing the polarity of the plastic film by oxidation, thereby changing its surface structure. These methods include discharge (such as corona or spark) treatment, flame treatment, ultraviolet radiation treatment, and treatment with acid (such as sulfuric acid or chromic acid). Among them, corona treatment is highly regarded for its simplicity and popularity. The effect of corona treatment is affected by many factors, including the output power of the treatment equipment, the distance between the two electrodes, the discharge area of the electrodes, the treatment speed, and the treatment method and number of times. The treated film should be printed immediately, otherwise it may fail. During the EDM process, the polymer may cross-link due to the free radical reaction generated by corona discharge, resulting in a rough surface and enhanced wettability to polar solvents. This treatment can usually significantly improve the printing properties of plastic films. In addition, to further improve the printing effect, antistatic additives such as trihydroxylaurylamide ethyl quaternary ammonium perchlorate can be used to enhance the static charge decay effect, thereby improving the adhesion of the ink. In gravure and chiral printing, the wettability of solvent-based inks has been further optimized. Printing method Plastic films use flexographic, gravure and screen printing technology, and it is particularly important to choose the right ink, especially gravure printing often uses synthetic resin and pigment blended ink. The printing methods of plastic films mainly include flexographic printing, gravure printing and screen printing. For gravure plastic films, the commonly used ink is a colloidal fluid formed by fully grinding and dispersing synthetic resins, alcohol organic solvents and pigments. This ink has good fluidity, printing performance and rapid drying, and is particularly suitable for gravure rotary printing on polyethylene, polypropylene and other films.