PFFC - February 2008 - (Page 42)

08104adR1 1/17/08 9:07 PM Page 1 COATING LAMINATING Figure 2. Examples of Defects from Contaminated Solution RDSPECIALTIES.com Fiber Dark Field Bright Field Large Gels Visit us online for product specs, problem-solving hints and information about our rods, lab products and custom solutions. Or give us a call at: Provided by Dark Field Technologies Inc. 585-265-0220 RD Specialties • 560 Salt Road • Webster, NY 14580 (585) 265-0220 sales@rdspecialties.com • www.rdspecialties.com PFFC-ASAP 133 contaminants can lead to a wide variety of spot and repellent defects. The coating solution also can contain gel particles from undissolved polymer in the mixing process. An estimate can be made of contamination levels by visual examination of solution, making a small amount of coating for examination under a microscope. Chemical contaminants or the wrong ingredients occasionally are found in coatings. Thermal analysis and spectroscopic techniques can be used to estimate purity and take corrective action before coating, if needed. Microscopy also can be used by coating on a transparent substrate and examining the coating. Examples of defects from contaminated solution are shown in Figure 2. Particle Size product from agglomeration point defects and inadequate product performance. There are several methods to consider: laser particle size analyzer, Coulter resistance particle counter, and microscopic image analysis techniques. In the last technique, image analysis software calculates particle size and distribution of sample particles being studied under microscope. Edward D. Cohen is a technical consultant for the Assn. of Industrial Metallizers, Coaters & Laminators (AIMCAL). He has 40+ years of experience in research and manufacturing technology. Contact him at 480-836-9452; cohened146@aol.com. The views and opinions expressed in Technical Reports are those of the author(s), not those of the editors of PFFC. Please address comments to author(s). Many coating formulations are dispersions. In these formulations the particle size is important for the product function and coating quality. Therefore the particle size can be measured after dispersion preparation to ensure it is within specifications. Monitoring in the production unit will ensure quality and provide a reference database in the event particle size problems are incurred. Agglomeration of the particles encountered at the shear rates during the coating process can lead to defective PFFC-ASAP 134 42 | FEBRUARY 2008 Additional Resource For a more detailed discussion of viscosity and surface tension in the web coating process, see Coating and Drying Defects: Troubleshooting Operating Problems, second edition, by E.D. Cohen and E.B. Gutoff, John Wiley and Sons, New York, 2006. WWW.PFFC-ONLINE.COM http://www.mtipolyexe.com http://WWW.PFFC-ONLINE.COM

Table of Contents Feed for the Digital Edition of PFFC - February 2008

PFFC - February 2008 Contents First Glance Calendar of Events From the Editor Web Lines Process Management News Clips Narrow Web & Label Reporter Narrow Web & Label What’s New Products Carton & Box Reporter Offset Printing A Triple Ply: Coating & Laminating Global Market Is Strong for Vacuum-Coated Products Melamine Innovation: A New Choice for Barrier Coatings How To Optimize Your Coating Solution’s Properties What’s New Products Contract Services Directory Custom Marketplace What’s New Products Services Directory Classified Marketplace Advertisers Index Experience Speaks

PFFC - February 2008

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