While PET is one of the fastest growing sectors of the beverage bottling market, taking over from glass and cans as the container of choice, its use has been mainly limited to fizzy drinks andwater.
PET has the practical benefit of being lightweight, shatterproof and recloseable.
It is also completely recyclable, giving it an edge under the EU's new regulations on reducing packaging waste.
However PET, and plastic in general, is not very good at keeping oxygen from permeating the container and reducing the shelf life of such products as juices, teas and flavoured water.
Oxygen has adegrading effect on flavour, colour and vitamin content for many beverages.
Now Philadelphia-based Constar International says it has developed a material that when blended with monolayer PET, binds oxygen, thus preventing the degradation of products such as juices, teasand flavoured water.
The product, called DiamondClear, is currently being tested before being submitted for regulatory approval.
Oxygen "scavengers" minimise the permeation of oxygen through the container bychemically binding the molecules.
Paul Prinko, Constar's marketing manager, told FoodProductionDaily.com that the company's DiamondClear represents a breakthrough in PET oxygen scavenging technology by offering both the clarity of glass and an economical monolayer structure.
"The economics of the DiamondClear monolayer solution is superior to other barrier methods," he said in an interview.
Constar is among a number of container manufacturers who have been searching for a solution to PET's oxygen problem.
The company first developed Oxbar, a multi-layer oxygen scavenger.
However more work was needed as Oxbar required beverage makers to invest in multilayer injection equipment.
Such multilayered solutions also pose another problem.
They can separate or delaminate under temperature or pressure stress, leaving an unattractive looking container.
The company then developed MonOxbar, a monolayer barrier material which cost less than Oxbar.
However MonOxbar plastic has a slight pearlescence and haze, which reduced its attraction.
Competitorsalso developed multilayered bottles and coatings to keep the oxygen out, but these suffer from similar disadadvantages.
With DiamondClear, a material that can be blended in a monolayer PET bottle, Constar believes it has found a winner.
As the DiamondClear material is blended at the preform injection stage, the technology works equally well with one-step and two-step injection stretch blow molding operations, eliminating the needfor high cost co-injection equipment necessary for multi-layer barrier systems.
Unlike systems to apply internal or external barrier coatings, DiamondClear preforms can be produced centrally, then shipped to any blowing location.
Constar believes that its "barrier in the preform" solutions provide scalability and flexibility.
Unlike currently available monolayer scavenger systems, the technology produces abottle with clarity equal to plain PET and with higher gloss, Prinko said.
Once its passes regulatory Constar plans to market DiamondClear PET containers to juice, ready-made teas and flavoured water bottlers.
PET can also be used for condiments such as ketchup and forpasta sauces and jams.
Constar expects the new plastic to be available on the market next year.i
The company is among the top five PET manufacturers in the US.
It also has joint-venture production plants in Holland, the UK, Turkey and Italy.
For the second quarter 2005 the company reported net sales of $265.4 million, a 17.4 per cent increase over the same period last year.
The company said the growth reflects the pass-through of increased resin prices, increased shipments of both conventional and custom products in the US and favorable foreign currency translation.
The increased net sales were partially offset by price reductions implemented to extend key long-term contracts and meet competitive pricing as well as reduced volumes in certain European markets.
External links to companies or organisations mentioned in this story: Constar International