Polyvinylchloride recycling

The ability to make PE with properties that fall outside these limitations would lead to a tremendous expansion of uses for this polymer, for example replacing flexible polyvinylchloride (f-PVC), which cannot be incinerated or recycled, thermoplastic polyurethanes (TPUs), or thermoplastic vulcanates (TPVs). 

The most difficult recyclates are the MSW, which usually consists of more or less dirty plastics of various types and sources. According to one report [15] the plastic portion of MSW contains typically 50% PE (mainly low density polyethylene, LDPE), 8-14% polypropylene (PP), 15% polystyrene (PS), 10% polyvinylchloride (PVC) and 5% polyethylene terephthalate (PET), and 5% other polymers, while the hard packaging fraction consists of approx. 60% of PP and HDPE [16]. 

In this study, Raman spectroscopy and pattern-recognition techniques were used to develop a potential method to differentiate common household plastics by type [87-89], which is crucial to ensure the economic viability of recycling. The test data consisted of 188 Raman spectra of six common household plastics high-density polyethylene (HDPE), low-density polyethylene (LDPE), polyethylene terephthalate (PET), polypropylene (PP), polystyrene (PS), and polyvinylchloride... 

The synthesis as well as the recycling and disposal of halogenated compounds such as Polyvinylchloride (PVC), flame retardants (for example Tetrabromobisphenol A), y-Hexachlorocydohexane (y-HCH), Hexachlorobenzene (HCB) leads to the formation of byproducts and residues. Polymers, for example, as well as printed circuit boards or shredder residues include problematic substances which, for ecological reasons, cannot be passed on to the environment but have to be supplied to a specific and proper recycling or disposal process. Prior to this background so called "Supercritical Fluids" are of special interest. Supercritical fluids can be used for the synthesis of polymers in an enviromentally friendly way as well as for recycling and disposal processes. 

Some plastics wUl soften and harden repeatedly as they are heated and cooled. This property is described as being thermoplastic. Thermoplastic materials are easy to recycle because each time they are heated, they can be poured into different molds to make new products. Polyethylene and polyvinylchloride are examples of this type of polymer. 

Plastics are classified based on recyclability into thermoplastics and thermosets. Polyethylene (PE), polypropylene (PP), polyvinylchloride (PVC), etc., are some of the thermoplastics and phenol formaldehyde, urea formaldehyde, etc., are examples of the thermosets. Both thermoplastics and thermosetting materials may be molded and then cooled to obtain the end product. Thermoset once molded cannot be either softened or reprocessed. 

Y = miscible N = immiscible HDPE High-density polyethylene LDPE Low-density polyethylene PET Polyethylene terephthalate PVC Polyvinylchloride Reproduced with permission from V. Goodchild, Introduction to Plastics Recycling, 2 Edition, Smithers Rapra Technology, Shawbury, Shrewsbury, UK, 2007, Table 4,1. ... 

Thermoplastics consist of long chain molecules that are produced from small molecules (called mers) by a polymerization process. An example of the formation of a typical polymer is given in Fig. 9.2 where polyethylene is produced from the monomer ethylene by application of heat, pressure, and a catalyst. When the resulting polymer is cooled, it solidifies. When reheated, a thermoplastic such as this will become liquid again. Due to this reversible liquid-solid conversion, scrap thermoplastic material may be recycled. Other thermoplastics are polypropylene, polyvinylchloride (PVC), polystyrene, polytetrafiuoro-ethylene (PTFE), polyesters, polycarbonates, nylons, cellulosics. 

To illustrate this relationship, consider a random ethylene copolymer of a density 0.856gcm" containing 19mol.% 1-octene comonomer. At room temperature, the material is elastic, or capable of recovering its size and shape after deformation. However, the copolymer loses the desirable properties of an elastomer at higher temperatures for example, the material has a compression set, a measure of a material s ability to recover its size after compression, of 100% at 70 °C (Figure 2). The ability to make PE with properties that fall outside these limitations would lead to a tremendous expansion of uses for this polymer, for example, replacing flexible polyvinylchloride (f-PVC), which cannot be incinerated or recycled, or more expensive thermoplastic polyurethanes (TPUs) or thermoplastic vulcanizates (TPVs). 

Commodity (CUT < 75 °C) a category which includes high and low density polyethylenes (HDPE and LDPE), polypropylenes (PP),styren-ics (PS), acrylics (PMMA), and polyvinylchloride (PVC). For recycling these resins are identified with a numbered triangle, namely 2 = HDPE, 3 = PVC, 4 = LDPE, 5 = PP, 6 = PS. The category 1 denotes engineering (PET) and all others are marked as 7... 

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