| Abstract [eng] |
Plastic is one of the most popular packaging materials in the 21st century. Currently, there are very many kinds of polymer materials, they have different properties and potential applications. Some are suitable for the food industry and intended to come into contact with food, others are resistant to chemical compounds, they are intended for chemical industry and so on. The main objective of this study is to determine the influence of polymeric materials physical parameters on the quality of imprints in flexography. In this study surface tension and electrostatic field physical parameters of polymer materials are discussed. These parameters are not directly inter-related but both of them have an effect on the final product quality. Plastic can be described as a hydrophobic material, poorly wettable by liquid. To improve wetting, printing materials manufacturers process the printing surface of printing materials with corona discharge, but time has a negative impact on wetting properties. In order to find out with what minimal surface tension it is possible to print qualitatively, this investigation of surface tension has been made. During it the lowest values of surface tension, ensuring satisfactory printing quality, were determined, a change in surface tension depending on the corona discharge power parameters was identified, and optical change depending on the surface tension values was analyzed. It is possible to pre-determine the suitability of input material for printing, if we know the minimal allowable limits of surface tension. The plastic also has the ability to easily receive electrostatic charge. At the time of printing or processing, plastic films constantly contact various surfaces, and receives the unwanted electrostatic charge. An electrified film roll causes many problems for the customer. Static charge attracts dust and other impurities from the environment, making it harder to handle this material on packaging lines. An attempt was made to eliminate this phenomenon through the use of passive measures for static charge removing based on grounding principle, however, the desired effect was not achieved. After analyzing the literature, it was found that active measures for removing electric field (ionizers) can solve this problem. In the course of investigation the suitable place for mounting ionizers in a longitudinal cutting/rewinding device Jurmet500 was determined. As well as the influence of ionizers on the process of electrostatic field reduction. Investigation of improvement in printed products quality was carried out by JSC “Reprodukcijos spalvos“ (Reproduction colors), along with the Kaunas University of Technology. JSC “Reprodukcijos spalvos“ company providing the services of flexographic printing. Company's main manufactured products include: adhesive labels, unprinted labels, barrier packaging films, and wrap bottle labels. |
