10 Oct 2001
PET: Packaging with an environmental edge
Recent legislation in Germany considers the single-use, recyclable PET bottle as ecologically unfavourable. Dr. Bram Opschoor, who helped to develop the PET bottle for carbonated drinks almost 30 years ago, gives his view. From 1968 until 1975, Dr. Opschoor worked for Akzo Plastics. Today he is Technical Advisor for PET Container Recycling Europe (PETCORE).
"Having spent many years on the development of the PET bottle, I feel almost personally embarrassed by the fact that even today its environmental benefits are still not fully recognised. The bottle is seen as just another plastic item and most people do not realise the advanced technological know-how needed for its design. When I first became involved in researching plastic bottles, exploding glass bottles were headline news in the Netherlands. In fact, experiments with exploding 1.5 litre glass bottles demonstrated that there was real danger for consumers.
Material prevention
"Our first attempts with plastic were unsuccessful. The bottles deformed into balloons under the high CO2 pressure. It was only when we recognised the particular properties of polyester, that we began to make real progress. Polyester is a chain molecule with only the organic elements carbon, hydrogen and oxygen. It reinforces and strengthens on stretching into ordered semi-crystalline structures, due to the orientation of the chain molecules. The use of polyester as reinforcing yarn for tires is based on this property.
We found that similar reinforcing also occurred in the oriented bottles during stretching in two directions.
"Blow moulding of PET preforms stretches and orients the PET molecules in two dimensions and this yielded a very tough plastic bottle weighing only 45 grams to hold 1.5 liters of carbonated drink. This could be compared to almost 1 kg of glass needed for a 1 litre glass bottle. Further developments have led to an optimised blow moulding process which helped reduce the bottle weight to 35 grams - and even further reductions can be expected In the future.
"PET therefore is the only material which can provide a safe and light weight container for carbonated beverages with a capacity of 1.5 litres and over. As such it has become the first choice for family consumption across Europe. It offers a highly relevant contribution to the important issue of material reduction even if compared to refillable glass.
Recycling
"A second property of polyester provides the basis for easy recyclability. PET belongs to the class of condensation polymers called polyesters, meaning that it is built via a stepwise, reversible reaction. In contact with traces of water during extrusion some depolymerisation occurs, but this can be reversed during a so-called solid state polymerisation reaction. Some recyclers use solid stating to build even higher molecular weights than used in the original virgin bottle grades. They target demanding applications such as top quality strapping. The regenerated high molecular weight of high quality PET is also used for “back to bottle” applications.
"In Europe, recycling of PET bottles will reach a volume of 300.000 tonnes in the year 2001, representing a 20% annual growth. The major outlet for recycled PET [R-PET] is extrusion into fibres for textiles or industrial non-woven fabrics.
Life cycle analysis
"The properties and inherent benefits of PET should lead to a more positive interpretation of the advantages of PET as a material for the manufacture and use for containers. Surprisingly, this is not the case when the PET bottle is examined purely from an LCA point of view. It must be noted, however, that this is not caused by any adverse environmental effects but by the choice of impact method chosen to interpret the inventory of the LCA.
"The simplified illustration shows two approaches. The first has narrow system boundaries around the bottle. If recycling into fibres is incorporated in this system, the calculated recycling credits for bottles fall back with 50%, due to the appearance of the material weight of the
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1040 Brussels
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Notes for editors
PETCORE - PET Container Recycling Europe - is a non-profit association, whose key objective is to facilitate the economical recovery of plastic containers (with emphasis on PET bottles) through collection, reclamation and development of end uses for post-consumer bottles throughout Europe.
Members include : BP/Amoco ● Coca Cola ● Constar ● Continental PET Technologies ● Dow ● Du Pont SA ● Eastman Chemical ● Evian ● Kosa ● Kulleborn & Stenström ● M&G ● Pechiney ● Perrier Vittel ● Rexam Beverage Packaging ● Ryttylän Muovi Oy ● Schmalbach Lubeca ● Tetra Pak ● Wellman ●
Editorial enquiries
Machteld van Doornik
PETCORE
Nancy van Heesewijk
EMG