Discusses how films are made (extrusion, coextrusion, coating, etc), formulated, converted and used in various applications such as printing, lamination, metallization, etc., and function at the end user. en-us http://www.convertingmagazine.com/blog/530000453.html?nid=3988 Copyright 2008 Reed Business Information. Subject to its Terms of Use July 18, 2008 http://www.convertingmagazine.com/blog/530000453/post/590029659.html?nid=3988 In reply to a recent posting, DaveO asks: "Is it possible for different orientations in a 2D expanded-PET film to cause variable diffraction of beta particles of X-rays in a measurement device?" This is an interesting question, and I think, is related to the need to measure film thic… http://www.convertingmagazine.com/blog/530000453/post/880029488.html?nid=3988 The question that should arise from my last posting should be, "How do the crystals rotate?" Understanding this requires knowledge of the way crystals and amorphous phase polymers are combined together in the bulk polymer. In an amorphous polymer all of the chains can be readily imag… http://www.convertingmagazine.com/blog/530000453/post/1280029328.html?nid=3988 Films are produced from molten and solid polymers by stretching either the melt as in blown and cast films or the solid as in biaxially oriented PET and PP. In these processes crystal alignment is observed which can affect some film properties. In general when stretching a molten poly… http://www.convertingmagazine.com/blog/530000453/post/1790029179.html?nid=3988 Film optics and especially haze are important usually, but not always with a desire for clearer films. In most semicrystalline polymers the difference between the density of the crystal and the amorphous phase drives light scattering which is a primary source of internal haze. Earlier bl… http://www.convertingmagazine.com/blog/530000453/post/650029065.html?nid=3988 Anandh Balakrishnan of the University of Oklahoma's Nanocomposites lab asks: What is the exact relationship between shrinkage and orientation? What thicknesses are we talking about in such cases? Well, there is no unique relationship between orientation and shrinkage because of variations in s… http://www.convertingmagazine.com/blog/530000453/post/710028671.html?nid=3988 I thought I'd begin with a discussion on film orientation. Orientation is the alignment of polymer chains in a film in particular directions in the film. In general there are three primary directions we consider, two in the plane of the film and the third through the film. For our pur… http://www.convertingmagazine.com/blog/530000453/post/860028086.html?nid=3988 I was recently asked the question as to what impact does blown film blow up and draw down have on seal strength. However, the answer is a little complex because of what seal strength measurements really measure. What do I mean? Well for instance in heat seal strength measurements the … http://www.convertingmagazine.com/blog/530000453/post/670027867.html?nid=3988 Please excuse my absence during the past week. I have physically moved my office and home to a new location and was very busy moving my rheology lab as well as my tools and belongings. My wife handled most of the organizing and I did a lot of work as well. So please excuss me. http://www.convertingmagazine.com/blog/530000453/post/660027866.html?nid=3988 It seems a bit unusual but in many instances it is easier to make film than it is to wind the film. In an earlier posting I spoke about the formation of a defect called “tin canning” which was due to the over tensioning of the film as it is wound. This week I am out making a v… http://www.convertingmagazine.com/blog/530000453/post/700027470.html?nid=3988 During a couple of my last postings, I discussed the use and behavior of viscosity data curve fit to a particular equation. A problem exists in that there are few really good curve-fitting programs available to perform the fit with high quality and low cost. I was fortunate to have access … http://www.convertingmagazine.com/blog/530000453/post/1130027313.html?nid=3988 The other day while discussing a question about draw down, I said that one way to define was the ratio of the melt speed exiting the die to the film speed after the film is quenched. This is sometimes called the haul off speed. So how do you estimate the melt velocity? Basically you… http://www.convertingmagazine.com/blog/530000453/post/1190027119.html?nid=3988 Medhat asked the question "How does the draw down ratio affect on the film properties?" from the March 4th posting on film manufacturing methods, and because the posting is focused on cast films, this is how I will approach the answer. However, I will comment on blown f… http://www.convertingmagazine.com/blog/530000453/post/1700026770.html?nid=3988 I thought I would start a series on moisture barrier improvement as it is a key barrier property for many substrates and in particular for substrates used for packaging, and especially for food packaging. In both industrial and food packaging, the level of moisture barrier which is important wi… http://www.convertingmagazine.com/blog/530000453/post/1520026552.html?nid=3988 Hello, I recently returned from a technical conference put on by the Society of Plastics Engineers (SPE) and it was a worthwhile trip. In addition to the many fine technical papers it is a fine place to meet peers in our industry and to renew friendships. There are far to many papers … http://www.convertingmagazine.com/blog/530000453/post/380025438.html?nid=3988 The use of polymer processing simulation packages for complex die and extrusion flow problems as well as the calculation of melt pipe pressure drops requires the use of accurate, corrected viscosity data to insure the best results. However, the viscosity data is often times the weakest link in … http://www.convertingmagazine.com/blog/530000453/post/1360025936.html?nid=3988 Hello, I am a little behind in blogging this week so hope you don’t mind a little less technical one tonight. Continuing along the recent viscosity focus, I measured my first flow curve around 1975 to start my study of polymer melting behavior in an extruder. That is where I first… http://www.convertingmagazine.com/blog/530000453/post/350025235.html?nid=3988 One of the best things you can do to improve the productivity of a film (or any line) is to increase the output of a product. For film products this means increasing the line speed. Several things happen which affects the potential for a melt disturbance of the third kind when we do this.&… http://www.convertingmagazine.com/blog/530000453/post/1230025123.html?nid=3988 In my last post, I spoke of making sure the outer layer was lower viscosity than the inner layer in a two- or three-layer coextrusion. How do I know this to be true? Well, let’s look at what is happening in the flow of a polymer melt. There is a phenomenon called encapsulation, … http://www.convertingmagazine.com/blog/530000453/post/980024898.html?nid=3988 When we coextrude films, it is necessary to have careful control of the melt rheology of each layer. If we don’t, then we are prone to get a melt disturbance. Now melt disturbance is a rich word and will mean many things to many people so it will be important to decide what we mean w… http://www.convertingmagazine.com/blog/530000453/post/930024693.html?nid=3988 The attached graphs came from US Patent 6,680,097 B1 which is titled "Easily removable label for reusable containers” and uses film shrinkage to help in recycling containers with labels and makes use of film shrinkage in a very unusual manner, to my thinking. The curves show TD (tran… http://www.convertingmagazine.com/blog/530000453/post/200024420.html?nid=3988 When designing a modern coextruded film you are combining polymers to obtain a set of properties that you cannot obtain from a single polymer. That of course is because no single polymer has all of the desirable properties necessary for a modern film. Several polymers are fairly capable an… http://www.convertingmagazine.com/blog/530000453/post/420024242.html?nid=3988 What exactly is FDA approval for substrates? Well, for starters, FDA does not approve substrates. What they do is to enforce the regulations of the law as defined in the Federal Food, Drug, and Cosmetic Act and additional laws enforced by FDA Code of Federal Regulations–Title 21. I… http://www.convertingmagazine.com/blog/530000453/post/1900023990.html?nid=3988 Today, there are many coextruded films containing a wide range of polymers combined together. In many cases the film layers are symmetrically placed and the stresses are balanced about the center line of the film. In this case the films will generally remain flat and curl free. Howeve… http://www.convertingmagazine.com/blog/530000453/post/130023813.html?nid=3988 While looking through my reference materials this weekend for heat shrinkage data for films, I used a fine reference which is focused heavily on oriented films and a special focus on shrink and stretch films. The book is “Plastic Films For Packaging”, Calvin J. Benning, Technom… http://www.convertingmagazine.com/blog/530000453/post/910023691.html?nid=3988 In my earlier answer to Juan, I discussed the shrinkage characteristics of various films relative to a specification. During this, I said that the best dimensional stability, aka shrinkage, data was data as a function of temperature. That is primarily because a single temperature does not …