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Mustafa Bilgin and Johannes Backhaus
E-mails: email@example.com; firstname.lastname@example.org
University of Wuppertal, Rainer-Gruenter-Straße 21, 42119 Wuppertal, Germany
Smart materials are based on chemical-physical processes that react to environmental factors or a specific stimulus. These factors or a predefined stimulus lead to structural changes. In this way, several smart materials can react to various influences such as temperature, UV light, or other. Smart materials of the type of hydrochromic inks change their colour under the influence of water or humidity. This stimulus-induced colour change process can occur in either reversible or irreversible form. Irreversible hydrochromic inks are preferable for a significant indication of the influence of water or moisture. Therefore, this research project focuses on the development and investigation of an irreversible hydrochromic ink for piezoelectric inkjet printing. For this purpose, the theoretical aspects of the chemical compound are discussed and the concept behind an irreversible hydrochromic ink is introduced. Several concentrations are evaluated and characteristic properties like viscosity, surface tension, particle size, and character-istic remission are analysed.
Keywords: smart materials, colour irreversibility, piezoelectric inkjet, spectrophotometry
JPMTR 136 | 2004 Original scientific paper
Optimization of water-based ink formulation based on different NCO : OH ratios of polyurethane dispersion
Shilpa Anchawale, M P Raghav Rao and Yogesh Nerkar
Department of Printing Engineering, PVG’s College of Engineering and Technology, Savitribai Phule Pune University, Pune 411009
Due to environmental concerns presently water-based inks are in demand in packaging and label printing, when the application is on paper and paperboard. But these inks are found to be incompatible while printing on a non-porous substrate like the films of polyethylene and polypropylene which are majorly used in the packaging industry for printing. Adhesion as well as optical properties (gloss) of water-based ink deposited onto the polymer film substrate are critical in flexible packaging. Hence the objective is to optimize water-based ink formulation for specific type of binder, its percentage, and percentage of other ingredients such as surfactant and polymer emulsion to achieve the complete adhesion and maximum gloss, which is utmost important for the growth of the water-based ink market in flexible packaging. The design of experiments (mixture model) was conducted to formulate water-based inks by varying the percentages of pigment–binder ratio (resin percentage), surface wetting agent, and polyethylene-based polymer emulsion. Scotch tape qualitative test method was used to measure the adhesion of ink. Adhesion percentage was calculated by analysing the area of ink which remained intact on the substrate. Data was analysed by using the multivariate data analysis method. This model was used to optimize the formulation for complete adhesion of water-based ink on the film substrate. The model explains that complete adhesion of water-based ink on polyethylene sub-strate takes place at 35.24 % of resin (1 : 1.5 pigment–binder ratio), 1 % of polymer emulsion, and 0.3 % of surfactant. Complete adhesion is observed for 1.35 and 1.4 NCO : OH ratios of polyurethane dispersion. Response surface design was used to find out the effect of binder and surfactant on the gloss of ink. The response surface model explains that surface tension is the dominant parameter for improving the gloss of ink on the substrate. Maximum 80.5 % gloss was observed for higher means at 1.4 NCO : OH ratio of binder and when 0.3 % of substrate wetting agent was used.
Keywords: adhesion, gloss, surface tension, flexography, statistical analysis
JPMTR 137 | 2005 Research paper
George Shields1, Alexandra Pekarovicova2, Paul D. Fleming2 and Jan Pekarovic2
1 UPM Kymmene Co.
2 Center for Printing and Coating Research, College of Engineering and Applied Science, Western Michigan 4601 Campus Drive, A-217 Parkview, Kalamazoo, MI 49008-5462
Paper properties and their role in preventing lateral web movement from cross machine air flows in the drying section during normal heat set web offset litho printing operations were examined. Tensile properties of sheets were measured at various moisture contents and then used to determine the equilibrium stress–strain relationship for papers at moisture contents typical of heat set web offset printing. Air permeability, creep, hygroexpansion, and ultrasonic measurement of tensile stiffness orientation module were evaluated against lateral web movement on heat set web offset litho press. It was found that the only item of interest from these results with respect to the lat-eral movement performance is the ratio between tensile stiffness orientation modules in the machine direction and cross machine direction, indicating orientation of the fibers in the paper web, and showing that more oriented fibers are less likely to shift on heat set web offset litho printing press. Understanding the effect of water absorption and absorption rate on the stress–strain relationship of paper may yield further understanding of web break tendency during heat set web offset printing.
Keywords: fiber orientation, tensile stiffness index, water absorption, stress–strain in paper, creep, hydroexpansion
JPMTR 138 | 2010 Case study
Influence of properties of materials for solventless lamination on the bonding strength of multilayer packaging
Vyacheslav Repeta, Yurii Kukura, Volodymyr Shibanov, Ihor Myklushka and Valentyna Kukura
E-mails: email@example.com; firstname.lastname@example.org
Faculty of Publishing and Printing Information Technology, Ukrainian Academy of Printing, 19, Pidholosko St., Lviv, 79020, Ukraine
The article presents the study of the bonding strength of multilayer polymeric packaging films, the use of which is one of the directions of development of the flexible packaging technology to ensure high barrier properties and strength of packaging. The dependence of the viscosity of two-component polyurethane adhesive on temperature and time has been studied. During the research, polymer films of the different chemical structures have been selected: polyethylene terephthalate, polypropylene, including the metalized one, and polyethylene. The wetting of the selected polymer film surface with polyurethane adhesive has been studied, the value of their surface energy has been determined, and multilayer systems (laminates) have been formed in production conditions. It has been found that the value of surface energy has a great influence on the formation of laminates with high bonding strength. The surface energy components have been identified according to the Owens–Wendt method to study the nature of the intermolecular interaction in the adhesive bonding. The correlation dependence between the surface energy and its components has shown that the adhesive bonding strength increases as the polar component increases. In general, it has been found that all the systems under study have provided the sufficient strength for laminates (multilayer packaging).
Keywords: film, adhesive, viscosity, packaging strength, surface energy
JPMTR 2001 Professional communication