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FLEXO Magazine : May 2012
plications. Special pressurized systems are available for corona treating when printing with solvent inks as well. Most flexographic printers will incorporate a watt density controller to ensure the cor- rect amount of treatment is applied to the film across varying line speeds. In most cases, treating the entire width of the web is required. However some applications, such as printing of stand-up pouches or bags require selective treatment. It is important not to treat the heat seal portion of the pouch. If the heat seal section runs across the width of the web direction a skip treat controller is used. The controller automatically turns the corona treater on and off at precise times to create treated and untreated areas of the web. If the heat seal areas run the length of the web in lanes, then a segmented treater is used. Metal electrode seg- ments enable operators to select pre- cise lanes for treatment and non-treat- ment. Pattern corona treating is more complex, but can be accomplished with a combination of skip treatment & lane treatment. This provides complete flexibility over the areas of the web that require treatment. For printers not achieving the results they desire with corona, employing atmospheric plasma surface treatment is also an option. Atmospheric plasma systems utilize unique gas chemistries to clean, etch and functionalize surfaces to produce results not possible with corona. Plasma treatment can produce higher and longer lasting results than corona treatment. n About the Author: Rory A. Wolf is a recognized industry resource in the field of polymer surface modification, and has 28 years’ experience within international positions in the plastics and packaging industries. He has specific experience in polymer-based flexible packaging, poly- mer surface modification systems, and printing industry segments. Wolf holds a Masters in Business Administration from Marquette University, Milwaukee, WI. He is currently vice president of business de- velopment at Enercon Industries Corp. , Menomonee, Falls, WI. He has published 28 technical papers, 38 industry articles, and two books on the topic of plastic surface modification by atmospheric plasma technology. His current professional affiliations are: • Division Council Member, PLACE Division, TAPPI • Board Member, Society of Plastics Engineers Decoration & Assembly Div. (SPE) • Member, Society of Plastics Industry (SPI) POP QUIZ ANSWERS Below are the answers to the “pop quiz” posed at the beginning of this Surface Treatment I.Q . article. IQ Answers: 1. This study, conducted by Behudin Mesic, et al. , examined the tendency for flexo ink to spread on the surfaces using contact angle measurements. Tri- als revealed that the surface energy of the protected sheets decreased with time, but not as much and not as quickly as that of the unprotected LDPE sheets. In the case of the protected LDPE film, the percentage of uncovered areas and mottling after printing remained constant, but for the unprotected sheets mottling increased with increasing time after the corona treatment. No significant differences were seen in the other print quality measures. 2. This study, by Thomas Schuman, et al. , indicated that intense corona treat- ment led to an undesirable increase in the Water Vapor Transmission Rate (WVTR) value. A less intense corona treatment preserved the WVTR value to a great extent, but the flexographic printability remained unsatisfactory. With plasma treatment, the water vapor barrier was not impaired. The flexograph- ic printability of the plasma-treated dispersion-coated substrate was good. www.flexography.org may 2012 FLEXO 43 MOUNT-O-MATIC DIRECT DRIVE For mounting flexo plates onto sleeves SLEEVE- MOUNTER PRE-PRESS EQUIPMENT FROM MODEST SYSTEMS TO THE MOST ADVANCED HIGH-TECH SOLUTIONS FOR ANY BUDGET www.flexologic.nl Innovation is the key to our success. FAMM Fully Automatic Mounting Machine Head Office AV Flexologic B.V. P.O. Box 252, NL-2400 AG Alphen aan den Rijn The Netherlands • Tel. +31 (0)172 434221 Mail: email@example.com PHOTOPOLYMER PLATEMAKING EQUIPMENT