PHYSICAL RECYCLING

Physical recycling, consuming a little more energy but restoring the level of entropy, seems to constitute a good solution. 

However, the entropy criterion despite its significant interest carmot be the only criterion used. We must consider health impacts which may prohibit the physical recycling of certain waste because of infection risks or radioactivity. We may want to avoid excessive transportation and therefore process waste on site in an existing factoiy. Some processes of valorization require a large quantity of waste and a consistent quality that caimot always be maintained Economic aspects play an important role and may limit the use of a good solution if appropriate incentives are not implemented. 

With regard to the objectives that we can achieve in light of the above, what about the valorization of plastic waste in practice It is found that few plastics are physically recycled compared with other materials used, which are similar to the case of packaging plastics (Figure 2.2). 

Figure 2.2. Rate of physical recycling of packaging (data from 2005 ADEME)...

These already low numbers are even lower if we do not limit ourselves to packaging waste. Then, it is only 7% of plastic waste which is physically recycled. We can, with difficulty, console ourselves by finding that the growth of the recycling of physical packaging was 360% between 1997 and 2004, while the volume of packaging added to the market increased by only 30% (Figure 2.3). 

In line with the lifecycle assessments presented earlier in this book, we can distinguish two classes of polymers which help to reduce a product s environmental impact. Ecoplastics include plastics derived from physical recycling and those derived from renewable resources (see Figure 10.10). 

In recycling, there are three main methods employed physical recycling, chemical recycling and incineration . 

In physical recycling, used plastics are reprocessed directly back to produce new (generally inferior quality) materials, for less demanding applications. The waste material already had certain additives from its previous history, and during its re-processing, new additives... 

There is no single method for treating polymethane (PUR) waste, due to the different quantities, qualities, mixes, and cleanliness. It is estimated that some 125,000 t of RIM polyurethane is used worldwide, 85% in automotive parts, mainly in bumper fascias. Current technologies for physical recycling of PURs are mainly directed towards flexible and rigid foams, but systems have also been developed for recycling reinforced reaction injection molded (RRIM) PURs, on the... 

PET recycling technologies have become well known and represent one of the most successful and widespread examples of polymer recycling. There are two methods of recycling PET waste one method involves physical recycling to produce PET flakes which are reused in a resin, and the other method involves chemical recycling via the depolymerisation of PET wastes. 

When physical recycling is done, care has to be taken in order to dry exhaustively the chips before processing in order to not diminish its molecular weight below the limit required to produce... 

There are various methods applied for the reprocessing of collected scrap in Turkiye, varying from almost completely automatic systems to primitive recycling facilities. Although physical recycling is carried out mainly, there is also one chemical PET recycling unit already on-stream. 

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