In Flexible Packaging, Barriers Are No Obstacles to Success
- Published: November 01, 2002, By Claudia Hine, Senior Editor
Success in business usually comes from finding ways to overcome barriers. But in the flexible packaging business, success is all about barriers, and in some cases, the higher the barrier, the better.
If your application requires moisture protection, you might choose a metallized biaxially oriented polyproplylene (BOPP). If you need oxygen or aroma barrier, you might opt for a metallized polyester (PET).
But now film producers are working hard to improve the oxygen transmission rate (OTR) characteristics of PP and to improve the moisture vapor transmission rate (MVTR) characteristics of PET. This will open up your choices when, for example, your package requires thermal stability in the seal area, and PET is more suitable for the application than PP.
Dan Roy, marketing manager of Toray Plastics America, North Kingston, RI, explains. “The main push for us, by improving either the OTR for BOPP or the MVTR for PET, really is foil replacement. About 30 percent of the foil market could be replaced with metallized substrates or transparent barrier substrates in some cases,” he says. Roy points to the changes taking place in dairy lidding, which traditionally has been die-cut foil. The trend now is to use a mono-film structure or a clear film laminated to paper. As companies invest in new packaging lines, they're going to roll-fed form/fill/seal equipment that actually forms the cup stock in-line and the lidding comes off a roll. “You reduce the cost of your lid by about 40 percent,” he says.
In choosing the right film, the conditions of use are critical in determining barrier performance and often are overlooked in the specification process, adds Jeff Wooster, value chain manager for flexible packaging in the North American Polyolefins and Elastomers business group of Dow Plastics, Midland, MI. “If a wet product is being packaged, then OTR of the packaging films should be measured at conditions of high humidity,” he explains. “If the package will be handled extensively, the reduction of barrier properties resulting from flex-cracking must be considered. For retort applications, the effect of the retorting process on barrier performance should be considered.”
Wooster says the recent development of commercially available blown film coextrusion equipment for producing films containing PVDC opens the door for making films that provide excellent oxygen and moisture barrier. “New equipment technology allows converters to coextrude materials and combinations of materials that previously had to be combined via lamination, a more expensive process,” he adds.
The growth of ethyl vinyl alcohol (EVOH) has had a big impact in the barrier market in the past few years, says Roy. “EVOH in resin form has taken the market by storm by offering an alternative to the converter. This allows them to buy vanilla grade films, whether its PP, or PET, or nylon for that matter, and then catch the value-add of the barrier component.”
What's down the road? “I think the biggest impact we're going to see on the market is what we call the ‘inorganic’ coating,” Roy says. “These are very transparent barrier coatings such as aluminum oxide and silicone oxide that are applied in chamber using a vacuum deposition process. These products are well-established in Asia. In Japan, where PVDC and other barrier additives are banned because of environmental laws, that market has extensively developed these types of barriers. So we're seeing a tremendous opportunity for growth in North America as people are looking for a transparent sheet that has as good if not better barrier characteristics than its metallized component.” What will that mean for converters and end-users in the future? More success!
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