Researchers manipulating high-barrier materials say the day is coming when soda pop and other drinks all are bottled in plastic, which is lighter, tougher and cheaper to use than glass. Work being done with liquid crystal polymers at North Carolina State University in Raleigh is making bottles less permeable than those made of PET. Researchers there successfully developed a detailed molecular structure of air-tight polymers. That can make it easier for resin makers to produce a commercially viable material.
Indications are that beer may be sold widely in plastic as well as glass and aluminum containers.
``Beer is like a Holy Grail in the sense that it is typically beyond the capabilities of conventional PET resins,'' said Benny Freeman, associate professor of chemical engineering at North Carolina State and principal researcher on the LCP team.
``But even with its limits,'' he added, ``you are starting to see PET used for beers in Canada, England and Japan.''
Freeman described LCPs as ``typically more-ordered materials than things like PET. They are things like Kevlar used in high-strength fibers.''
``There are no commercial bottles being made of this or of composites made of LCPs and conventional polymers. I've seen prototype beer bottles made with an LCP liner, so people are working on it. They're trying to get the thickness of the LCP layer down to reduce the cost of the bottles. You don't need much to do a really good job,'' Freeman said.
Freeman discussed recycling issues involved in LCP barrier technology.
``The ones we're working with are polyesters so they're not so difficult to separate from conventional polyesters. Also, for some markets, particularly outside the United States, they're looking at refill applications. If you could put a really high barrier inside PET it might help in those kinds of applications,'' he said.
The educator said refill PET pop bottles are sold in Europe and South Africa, where much of the growth for bottle resins occurs.
North Carolina State has a strong reputation for LCP research, which is focused on how small molecules, oxygen, carbon dioxide, and water are positioned and permeate through plastic. Most research during the past 25 years has been done at North Carolina State, the University of Texas at Austin and Syracuse University.
Recent developments in LCP research at the university were discussed by Freeman in a paper delivered in March at a meeting of the American Chemical Society.
For bottlers depending on the application, keeping oxygen out of the drink can be as important as keeping the fizz in.
``For beer, keeping oxygen out is the whole ballgame. Something like Coca-Cola is not nearly so sensitive to oxygen so the [carbon dioxide] is the main actor there,'' Freeman said.
A successful barrier could lead to use of smaller bottles, he added. ``The soda industry would really like to have a 12-ounce bottle. But, as you go to a smaller size, the amount of surface area of bottle you have per unit pound of soda you package goes up. The rate at which you lose COÃ is proportional to the surface area. The amount of COÃ you have to lose is proportional to the mass of the soda you are packaging. You are driving up the rate at which you lose it and driving down the reserve you carry around. You've got a couple of principals and both are working against you as package size gets smaller.''