What a difference a K makes.
Milliken & Co., the Spartanburg, S.C.-based specialty chemical company first introduced its Ultra Clear PP additive in 2007. But it took last year's K show in Düsseldorf, Germany to show the market what it could do.
“Ultra Clear PP has been on the market since 2007 but it's really taken off for thermoforming in the last year,” said Sami TK Palanisami, Milliken's marketing and sales manager (EMEA), at the Interpack exhibition in Düsseldorf in May.
“I think the issue in the past was that everybody thought that polypropylene was expensive and it's not recyclable — that's the major issue. So people went for PET.”
The recycling issue has become something of a green herring. True, PP isn't easily recyclable, but in one particular application — rigid packaging of convenience foods, where the trays are not generally recycled in any case — the case for recycling PP becomes stronger.
“We found a new solution,” said Palanisami. “[Converters] can add our additive to PP, at a similar cost to PET, but have all the advantages of PP. You can put it directly in a microwave. Normal PET cannot be put in a microwave. The sealing and peeling is much easier — for PET you need to heat at high temperature, or you need to use a coating, to seal it. It's lower density, and lower weight.”
Wim Van de Velde, marketing director plastic additives at Milliken, added: “Typically with a food container the sealing strength between the polyethylene film and the polypropylene is much stronger versus the polyethylene film and PET. For example, if you do drop impact tests, you're clearly going to see that the PET container is going to free away more versus the PP container.
“From an overall point of view, if you take everything into account, polyolefins are more sustainable, with a lower carbon footprint than PET. The energy to make polypropylene is lower. And when you incinerate it you get a higher energy recovery value. And your density is lower. So, put all these things together, and bring in a relatively competitive price, polypropylene makes a very good packaging material.”
Polypropylene's opacity, and relative cost, had made it an unlikely proposition for packaging use in the past. But bring transparency into the equation, and factor in rising polystyrene prices, and it becomes a far more competitive material.
Van de Velde said: “PET is still relatively cheap in Europe but not in the United States and Asia because, with all these shale gas developments, aromatics have become more scarce, and so the PET prices have gone up. All these things tend to play in favor of polypropylene.”
These advantages have already attracted a major retailer, Wal-Mart Stores's UK business, Asda. Van de Velde held up an Asda ready meal package and said: “You go from deep freeze to microwave, in the same packaging.
“At K, in October last year, we were talking to packaging converters and they thought that, with transparent thermoforming food packaging, they only had two choices: polystyrene or PET. They never would have thought they can use polypropylene, but the fact is, now that it's transparent, they can. This is really taking off in the UK and it's on the shelves now.”
One application is thermoformed lids for cold coffee and blended beverages. Traditionally both lid and cup had been PET.
Van de Velde said: “They first changed the cup. If you look [in Starbucks] there is small print on the cup, ‘this is made from polypropylene which produces 15 percent less waste than PET'. But the problem was that the lids were still PET, because PP could not be that transparent, with that glass-look. But these big companies have their internal recycling programs. And if you have two materials it's very inconvenient.
“But what's happened now is that, in the U.S., for sure, and also in other parts of the world, you're moving away from PET. So your cup as well as your lid now is polypropylene.”
