Techniques for selection and recycling of post-consumer plastics are closely related to the characteristics of plastic containers consumption, which are extremely diversified according to the geographical areas and the relevant law regulations governing activities in this sector.
In each area, socio-economic and legislative features as a whole determine the first stage of the recycling process, that is collection. This, in turn, influences the layout of the recycling plant which aims at the re-use of plastic materials reclaimed in the most economical way.
Hence the enactment oflaws which bind municipalities to recycle containers in general, as is the case in Germany, or in a more restrictive sense, in Italy, where recycle is limited to containers for liquids only.
On the other hand, consumption features play a major role in the choice of the materials to be recycled. So, in the United States materials chiefly recycled are PET bottles and PE containers; in France, on the contrary, they began to recycle PVC on account of the large quantity of such material used in the packaging of drinks. In Australia recycling includes PET and PE, whereas in Japan PET alone. In Italy plastics recycled are PET, PVC and PE.
In short, the material to be recycled and the enforced legislation are determinants for the choice of the collection system. In the United States, Australia, France, Austria and Switzerland, different fractions of post-consumer plastics are collected in the most homogeneous way possible.
In other countries, on the contrary, plastics are collected more heteroge-neously, that is to say, different types of plastics out of different types of manufactured articles, such as foil, containers, bottles, are collected together.
At any rate, collection must necessarily be a "differentiated" one, although the degree of differentiation may vary extremely. In Italy, collection, according to Law 475, is differentiated as far as recycle of plastic containers is concerned, whereas it is non-differentiated with regards to type of plastics, since liquids containers may be made of either PVC, or PET, or PE, or else.
The outcome of the collection system, therefore, constitutes the raw material for the recycling process. Consequently, as we are taught by experience in this field, the more selective the collection, the higher the degree of purity from foreign bodies in the final product.
In Italy, for instance, collection of liquid containers by means of plastic boxes, shows 15% to 20% contamination resulting from foreign bodies. Collection of drink containers carried out with the AZURE-Bottle-eater - an automatic machine installed inside supermarkets presents pollutants solely composed of other types of containers, and not exceeding 1%.
Aim of this paper is to present the more recent technologies of automatic separation of plastic items. A brief paragraph on a typical recycling plant of homogeneous plastics is also presented.
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