Here we discussed the provision of general information on plastics, their structures, chemical properties, uses, and environmental effects in addition to studying their types, availability, and methods of PET recycling that could be adopted.
When recycling polyethylene terephthalate or PET or polyester, two ways generally have to be differentiated: The chemical recycling back to the initial raw materials purified terephthalic acid (PTA) or dimethyl terephthalate (DMT) and ethylene glycol (EG) where the polymer structure is destroyed completely, or in process intermediates like bis-ß-hydroxyterephthalate.
Mechanical recycling is where the original polymer properties are being maintained or reconstituted.
Chemical recycling of PET will become cost-efficient only by applying high-capacity recycling lines of more than 50,000 tons/year. Such lines could only be seen, if at all, within the production sites of very large polyester producers. Several attempts of industrial magnitude to establish such chemical recycling plants have been made in the past but without resounding success. Even the promising chemical recycling in Japan has not become an industrial breakthrough so far. The two reasons for this are at first the difficulty of consistent and continuous waste bottle sourcing in such a huge amount at one single site and at second the steadily increased prices and price volatility of collected bottles.
Mechanical recycling or direct circulation of PET in the polymeric state is operated in the most diverse variants today. These kinds of processes are typical of small and medium-sized industries. Cost-efficiency can already be achieved with plant capacities within a range of 5,000 – 20,000 tons/year. In this case, nearly all kinds of recycled-material feedback into the material circulation are possible today.
Besides chemical contaminants and degradation products generated during first processing and usage, mechanical impurities are representing the main part of quality depreciating impurities in the recycling stream. Recycled materials are increasingly introduced into manufacturing processes, which were originally designed for new materials only. Therefore, efficient sorting, separation, and cleaning processes become most important for high-quality recycled polyester.
When talking about the polyester recycling industry we are concentrating mainly on recycling PET bottles which are meanwhile used for all kinds of liquid packaging like water, carbonated soft drinks, juices, beer, sauces, detergents, household chemicals, and so on. Bottles are easy to distinguish because of shape and consistency and are separate from waste plastic streams either by automatic or hand sorting processes.
Download Seminar Report
0 comments