Effect of Aminopropyltriethoxysilane on the Adhesion of Flexographic Water-Based Ink to Packaging Films

Plastic films are widely used in packaging, where high-quality printing on their surface is required. When printing on films, particularly with water-based inks, problems arise with proper ink adhesion to the substrate. As part of the ongoing research, formulas of flexographic water-based inks were developed, where aminopropyltriethoxysilane was used in various amounts as an adhesion promoter, its effect on the adhesion of inks to three types of films commonly used in packaging was determined, and the quality of prints was examined. The research included the tape test, the T-peel test, and the abrasion-resistance test, as well as measurements of the pH of the inks, contact angles, and optical properties of the prints and their gloss. As a result of the study, the type of film was found to be crucial to the effect of aminopropyltriethoxysilane on the adhesion of flexographic water-based ink to the substrate and print quality. An addition of 1.0%–1.5% makes it possible to achieve the best adhesion improvement (bonding strength increased by about 26, 35, and 102% for PE, BOPP, and PET films, respectively) while improving print quality—increasing the optical density of prints and their gloss. However, the use of 1.5% silane in ink has a significant impact on the color of the ink (∆E ranging from 2.2 to 7.8 depending on the film). The amount of the additive used (0.5 to 1.5%) of aminopropyltriethoxysilane in the ink would need to vary depending on the type of film to be printed.