A new comment from “David Tanner” was received on the post “Response to Query” of the weblog “Web Coating Blog”.
Comment:
I
would like to add to this post by saying that the Dyne Solutions that
referred to are availible from selected companies, in the UK and Europe
for instance CDE Products have manufactured Dyne solutions for over 20
years.
Response to Query on Curl
Edward D Cohen
In response to your question about curl when ink is applied to film, the curl is the usually towards the coated side of the film. It is caused by residual stresses in the coating applying a force to the substrate, which causes the substrate to bend. The stresses can arise form several causes. Stresses generated, as the coating shrinks during the drying process will cause curl if not relieved. The magnitude of these stresses will depend on the amount of shrinkage, the properties of the binder system, the substrate physical properties transition temperatures and stress relieving in the dryer. Often a high relative humidity et eh end of the dryer and in ambient air. A stronger substrate may also be needed.following diagram shows curl and stresses.
In response to your question about curl when ink is applied to film, the curl is the usually towards the coated side of the film. It is caused by residual stresses in the coating applying a force to the substrate, which causes the substrate to bend. The stresses can arise form several causes. Stresses generated, as the coating shrinks during the drying process will cause curl if not relieved. The magnitude of these stresses will depend on the amount of shrinkage, the properties of the binder system, the substrate physical properties transition temperatures and stress relieving in the dryer. Often a high relative humidity et eh end of the dryer and in ambient air. A stronger substrate may also be needed.following diagram shows curl and stresses.
The following diagram shows curl and stresses
Effective Networking, A Path Through The Information Overload
Edward Cohen
Even though we live on large planet, with large physical dimension (a Volume of 1.0832073_1012 km_ and a Mass of 5.9736_1024 kg); technologies such as the Internet, Information Sciences, World Wide Web, rapid digital communications ,easily accessible databases and search engines have made it a very small world. It now possible to instantly communicate with persons all over the world and to obtain technical information from most countries, businesses and Universities.
Continue reading "Effective Networking, A Path Through The Information Overload" »
A question that is often asked about the Web Coating Process is “ What are the one or two most critical areas of the process that I should concentrate on to obtain a coated product with high quality and low cost?”. A possible basis for this question can be found in an interchange in the 1991 movie “City Slickers”, between Billy Crystal and Jack Palance
NEW BI-MONTHLY POSTINGS WILL FOCUS ON THE DRYING PROCESS
Daniel Bemi Megtec Systems, is joining the Web Coating Blog as a contributing author. His focus will be on new bimonthly postings on all aspects of the Drying Process.
Drying and curing of coatings, along with other drying and annealing applications, are often a critical component of the coating and laminating process. While there are several good texts available on drying theory, there is a shortage of written materials focusing on application “know-how” and real world drying challenges. As such, AIMCAL will be introducing a bi-monthly posting of dryer-related technical articles beginning in January 2007. These postings will be aimed at bridging the gap between drying theory and application-based, process knowledge.
If you have a topic of interest that you would like to see addressed by our experts, please send your suggestions to Ed Cohen email cohened146@aol.com
Dan Bemi Email: dbemi@megtec.com Regional Sales Manager
MEGTEC Systems, Inc. 830 Prosper Road De Pere WI 54115
Phone: 262-255-3275 Fax: 262-255-3578
A flotation drying system often represents the longest web span between tension isolation points on an entire coating line. For this reason, web stability inside the dryer can be a concern. Common problems include troughs and wrinkles, edge flutter, and web shift. In order to identify and deal with these web-handling issues in a flotation dryer, we must first understand flotation principles.
Unlike roll support equipment where the heat transfer and web handling components of the drying process are independent (i.e. web handling via idler rolls and heat transfer via impingement air distribution nozzles or other forms of heat distribution), flotation dryers combine these process components into the functional design of the flotation nozzles or air-bars. Therefore, air-handling uniformity is far more critical to the web-handling performance of a flotation dryer than it is with roll support technology.
Continue reading "Troubleshooting Common Web-Handling Problems In A Flotation Dryer" »
This discussion is a continuation of the role of the Substrate in the coating & drying process which was started in a previous entry “Role Of The Substrate Part 1 Substrate Structure”. This part will discuss the interaction of the substrate with the coating and drying process and its role in final product coating quality and the formation of defects.
The substrate is an integral part of the coating system and it can cause a wide variety of defects, spots, poor adhesion, poor winding properties, coating weight non-uniformity, poor planarity and lay-flat. If the incoming substrate has defects and does not meet specifications, then it will lead to a defective final product. The Old adage Garbage In Garbage Out) definitely applies to the substrate and the coating process. Defective substrate when coated will lead to defective product.
The substrate used in the coating process is a key element in the successful operation of a web coating process. The substrate is the carrier of the active coating layer. The effect of the substrate on the coating process needs to be understood, optimized and controlled to insure quality and cost. Web and support are also terms used to refer to the substrate.
The major areas of technical importance for the substrate are:
• Substrate structure
• Surface Properties treatments and coatbility
• Mechanical Properties
• Defects Arising from Substrate
• Substrate Flatness
• Specification of Substrate
• Substrate Manufacturing
• Substrate Roll winding & unwinding
• Substrate web handling in coating machine
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