TAPPI Extrusion Coating Short Course

Published: September 26, 2013, By Tom Bezigian

There was a good turnout of about 55 people not counting instructors, mostly from the USA, but with several from overseas, including Southeast Asia.  As basic science and engineering doesn't really change much, the material covered was largely the same from the previous course, with a few notable exceptions.

Christine Ronaghan from Cloeren gave a marvelous presentation on the topic of coextrusion, delving into basic science, then the evolution of applied engineering from the original Dow coex technology to Egan's divider plates to plate technology to spool coex systems.  The only word that was missing from Christine's talk was "SIMULTANEOUS".  Coextrusion is the simultaneous extrusion of two or more layers of molten polymer material out of the same die, at the same time.  I can't tell you how many times this comes up in court and how much time, effort and money companies waste defending themselves against this otherwise obvious definition. 

Sam Iuliano of Nordson/EDI gave a nice talk on dies, contrasting and comparing those available as well as teaching about basic polymer processing in extrusion coating.  This is the one topic that I wish TAPPI would spend more time on versus simple papers on pieces of the puzzle.  To me, extrusion coating is a three legged stool comprise of equipment, materials and processing.  Sam, as well as Scott Weber of Lyondell-Basell, did an excellent job of bringing the extruder adapter into focus as a primary tool for controlling the extrusion process.

Another notable to me was the presentation by Scott Wagner of Pelletron, who discussed material handling and equipment available to help control and eliminate fines.  In a nutshell, specialty elbows exist to absorb the momentum change cause by curves in the conveying system rather than have that same momentum change be converted to heat, thus causing fines.

One real faux-pas in the short course was on the subject of "Gel" troubleshooting and prevention.  In that talk, gels were implied to be any contamination or defect which causes an optical disturbance in the product.  Gels have a narrow and particular definition in polymer processing, that being a high molecular weight, crosslinked portion of polymer whose molecular weight is so high, in the order of millions, that the gel cannot be melted.  In other words, instead of being a true viscoelastic material, capable of flow in many domains,  it is elastic material that cannot be melted with limited flow properties.  I feel the need to point this out, again because of the potential of misuse in the legal system in the United States.  Gels are not particles of dust, cardboard fiber, gasketing material, etc, that may be introduced into the extruder from extraneous sources.

All the being said, blues music is excellent in Memphis.  I prefer St. Louis or Texas BBQ to Memphis BBQ, but I suppose that is a subjective matter, better left alone.