GREENER PLASTICS
As green issues are very much in the news at the moment we shall take a look at what steps the plastics industry are taking to become greener.
Thermoplastic materials are almost entirely derived from oil, a dwindling natural resource. After years of investigation some viable alternatives are starting to come to fruition. Carbon Dioxide has been investigated as a basis for some polymers, such as polycarbonate and polyurethane.
Oranges are the Only Fruit
In
fact, US scientists have discovered a way to make plastics using orange peel
and carbon dioxide. This process offers hope that harmful greenhouse gases
could be harvested to be used in polymer production instead of pumping it
into the atmosphere. Orange peel contains limonene which is a carbon based
compound. It was a derivative of this oil –limonene oxide, which was used
in the process. The resulting polymer was very similar in character to
polystyrene.
Sweet Corn
Other developments have been based on polylactic acid (PLA). PLA is produced by the fermentation of corn sugars to produce lactic acid. This is then converted to PLA by polymerisation. At present this material does not possess the same levels of temperature tolerance of its hydrocarbon based peers so applications are limited.
Several approaches are being considered to overcome this problem whilst retaining biodegradability – the most promising are controlling the crystalinity of PLA, developing copolymers of lactic acid and other monomers, and blending PLA with other polymers.
Belu natural mineral water has launched the first compostable bottle in the UK produced from PLA. This composts completely in just 12 weeks. Also being considered as future products for PLA are fast food packaging, compostable bags and personal care products.
The Future
DuPont has undertaken a great deal of research and development in this field in an attempt to produce high performance thermoplastics from renewable sources. The first two products to market will be Sorona and Hytrel (new grades added to the existing polymer range).
Sorona is similar in performance to PBT offering good strength and stiffness with improved surface appearance and gloss. This new polymer should be available in mid-2007.
Hytrel is already well known as a polymer. The grades made with renewable resources show improvements in temperature range and elastic recovery when compared to current Hytrel. These new grades should be available towards the end of 2007.
The
key ingredient in these new polymers (Bio-PDO) is derived from corn sugar
using a patented fermentation process. The world’s largest aerobic
fermentation plant has been built in Tennessee and is a joint venture
between DuPont and Tate & Lyle Bioproducts.
The processes involved in the production of Bio-PDO use approximately 40% less energy than its petrochemical based counterpart. It is estimated that this will save the equivalent of 10 million gallons of petrol per year in producing 45,000 tonnes of Bio-PDO. DuPont has a corporate goal of deriving 25% of its revenue from renewable resources by 2010.
In the context of the entire polymer industry this is a tiny part but it is a bold move in the right direction. With the driving force of DuPont, one of the leaders in polymer development through the history of plastics, there is every expectation that thermoplastics produced from renewable resources will become an ever increasing proportion.
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