Journal of Print and Media Technology Research

Microstructure, morphology and properties of printing paper laminated with polypropylene film

2025-02-14T08:49:50+00:00

To improve design, reduce wear, and extend service life, lamination involves applying a thin polymer film to paper or cardboard using hot melt adhesive or a solution. Moreover, hot melt adhesive bonds well to a fairly rough or matte surface. If the surface of the paper or cardboard is smooth or glossy, then molten high molecular weight polymer adhesive does not always penetrate its micropores. Due to differences in melting temperatures between the polymer adhesive and the polymer film, the polymer adhesive does not bond strongly enough to the polymer film.
In this study, in order to increase the adhesive strength between paper and polymer film, glossy paper was laminated with polypropylene film using an adhesive solution of ethylene–vinyl acetate (EVA) copolymer. A polymer adhesive solution, unlike a melt, penetrates into the micropores of glossy paper and ensures strong adhesion of the polymer film to the paper surface. FT–IR spectroscopic studies of polypropylene, EVA copolymer, and laminated paper showed the absence of chemical interaction between them during the lamination process.
As studies on SEM-EDS analysis have shown, the adhesion interaction between the polymer film and the adhesive occurs due to ethylene units, and between the paper and adhesive due to vinyl acetate units. In contrast to the industrial sample with hot melt adhesive, in the experimental paper sample, near the polypropylene film, micropores are filled with a polymer adhesive solution. Elemental analysis of torn layers of laminated paper shows the presence of polymer adhesive in the micropores of the paper layer. The adhesive strength between layers of laminated paper is 20 % higher, and the penetration force is 40 % greater than that of the industrial sample.

Retroactive effect of variable tensile forces on lateral web motion and lateral registration errors

2025-02-14T08:58:06+00:00

The lateral position of a continuous web can be determined by a control roller at an angle to the longitudinal direction of web motion together with subsequent auxiliary rollers. However, a change in the tensile force changes this lateral position. The solution of the system of descriptive differential equations leads to a separate treatment of pure translation and pure rotation of the control roller. However, a resulting block plan for the dynamics of lateral motion was found, which is combined with the longitudinal mass flow and the retroactive effect of variable tensile forces on the lateral motion. Transverse and longitudinal register errors in the multi-roller system can be mapped together with the mass flow chain in the form of a multi-layer model. This enables extensive simulations of all system quantities as well as the design and optimization of control loops.

Natural plant dye inks set new challenges: analysing the interaction of anthocyanin-rich dye with modern calcium carbonate containing substrates

2025-02-14T09:02:28+00:00

Plant dyes are increasingly finding applications across a broad spectrum of print technologies, leading to replacement of conventional synthetic dyes and pigmented inks for a range of print media. Despite technical advances, industrial application faces some fundamental challenges of achieving the necessary critical print properties demanded when using such dyes. These include maintaining runnability, colour definition and fastness while retaining functional stability, the latter being particularly challenging since many prints are based on digital patterning adopting inkjet or flexographic methods. This study explores the fundamental interactions between an example pure dye ink, derived from Aronia melanocarpa, a member of the family Rosaceae commonly known as chokeberry, and specific substrate filler and coating components. Key interactive factors include ink formulation, the nature of dye chemistry in relation to substrate structure, its optical properties and constituent components. The acidity of the juice-based ink is mainly dependent on the amount of anthocyanin (ANC), a water-soluble phytochemical plant protective flavonoid, occurring together with other phenolic compounds. Novel experiments are reported in which interactive substrate components are isolated and studied directly in contact with the naturally acidic anthocyanin-rich ink. Coloration of the dye is confirmed to be pH-dependent, and, as a result, major challenges arise when acidic ink contacts alkaline substrate, which covers the majority of paper, board and cellulose-based packaging materials today, due to the dominance of calcium carbonate as the filler and coating pigment of choice. In parallel, dye imbibed into substrate pores surrounded by materials of contrasting refractive index lead to effective colour gamut changes as the ratio of transmitted light through dye and scattered light from surrounding materials changes. This effect is exemplified comparing high refractive index titanium dioxide (TiO₂) versus lower refractive index calcium carbonate (CaCO₃). Finally, a strategy is proposed aimed at controlling the interaction and enhancing the overall printing performance.