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Presentations 2015, 2016

iarigai Toronto 2016
iarigai, VIGC, IS&T at drupa 2016

iarigai VIGC, Brussels
Evolutions in food packaging printing

You are here: Conferences & Events * 2010 Montreal * Abstracts * 3. Improving printing process

3. Improving printing process

3.10 Surface and Structural Properties of EPDM and NBR Rubber Blankets

Gorazd Golob, Mladen Lovreček, Miran Mozetič, Alenka Vesel, Odon Planinšek, Marta Klanjšek-Gunde, Vilibald Bukošek

During our research work we studied surface properties of lithographic offset rubber blankets based on polar NBR/TM and non-polar EPDM elastomer blends, modification of surface free energy using oxygen plasma treatment and defunctionalization of surface properties using IR and UV high power laser devices.

Results of defunctionalization or modification of blanket surface properties using proper IR or UV laser are presented in this paper. Our investigation includes surface free energy determination using contact angle measurements with different liquids and calculation method by Owens Wendt, chemical analysis of the surface using FTIR ATR spectra measurement and analysis using KnowItAll software with database and dynamic mechanical (structural) analysis of elastomer samples. We studied properties of untreated and plasma or laser treated elastomer material as a basis for the improvements and understanding of new functionality of rubber blankets with discrete hydrophilic/oleophobic and hydrophobic/oleophilic areas.

After treatment with oxygen plasma we achieved higher level of total surface free energy and polarity with NBR/TM compared to EPDM rubber. The ratio of surface cleaning effect compared to chemical modification during oxidation process is still unknown but it seems that surface cleaning or ablation effect using oxygen plasma has stronger impact on surface free energy compared to oxidation.

After additional IR and UV laser treatment of the same the values of surface free energy did not return to the former state of untreated samples, as we expected. We are able to reach about half of water contact angle value differences only at EPDM sample.

Keywords: NBR rubber, EPDM rubber, oxygen plasma treatment, laser treatment, FTIR ATR spectroscopy, dynamic mechanical analysis
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3.11 Plate performance affects offset blanket piling

Kaisa Vehmas, Soile Passoja, Asko Sneck, Eija Kenttä, Antti Peltosaari, Jani Kiuru

VTT Technical Research Centre of Finland
P.O. Box 1000, FI-02044 VTT, Finland

Non-image area piling on blanket is considered as a process property of offset printing, which influence on print quality and press runnability. There is not a single reason for piling - it is always a combination of press settings and all the materials used in printing. In this study the role of the printing plates and fountain solution purity on piling build-up was clarified. It was found out that piling formation is sensitive to plate characteristics; different plates produced different kind and amount of piling on blanket surface. Ink spread to the non-image area of the plate as spots or tails and ended up on the non-image area of the blanket. The main reason for the non-image area piling was found to be the poor emulsion stability on the plate. The fountain solution itself did not cause non-image area piling on the blanket but it affected the mechanism of piling by interacting with the ink. With fresh fountain solution, the ink spread mainly as tails from the back edges of the dots, while with used fountain solution mostly ink spots were noted on the plate non-image area.

Keywords: heatset offset printing, thermal plate, CtP plate, piling
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3.12 Dynamic analysis of temporal moisture profiles in heatset printing studied with near-infrared spectroscopy

Carl-Mikael Tåg, Maunu Toiviainen, Mikko Juuti, Patrick Gane

Dynamic analysis of the water transfer onto uncoated paper, and its permeation and absorption into the porous structure were studied online in a full-scale heatset web offset printing environment. The moisture content of the paper was investigated at five different positions during the printing process. Changes in moisture content of the paper were studied as a function of web temperature and printing speed. Additionally, the influence of fountain solution composition on the pick-up by the paper was investigated. The water content of fountain solution transferred to the paper from the printing units was observed as changes in near-infrared absorbance. A calibration data set enabled the subsequent quantification of the dynamic moisture content of the paper at the studied locations. An increase in the printing speed reduced the water transfer to the paper and an increase in web temperature resulted in a reduction in the moisture content. Differences in the drying strategy resulted in different moisture profiles depending on the type of fountain solution used. As a conclusion, the near-infrared signal provides an effective way to characterize the moisture dynamics online at different press units.

Keywords: evaporation, moisture content, fountain solution transfer, heatset printing, water uptake
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