Recycled plastic identified

Contaminants in recycled plastic packaging waste (HDPE, PP) were identified by MAE followed by GC-MS analysis [290]. Fragrance and flavour constituents from first usage were detected. Recycled material also contained aliphatic hydrocarbons, branched alkanes and alkenes, which are also found in virgin resins at similar concentration levels. Moreover, aromatic hydrocarbons, probably derived from additives, were found. Postconsumer PET was also analysed by Soxhlet extraction and GC-MS most of the extracted compounds (30) were thermally degraded products of additives and polymers, whereas only a few derived from the original contents... 

Identification of the materials of construction (i.e., plastics, paper, metal, glass, elastomers, coatings, adhesives, and other such materials) should be identified by a specific product designation (code name and/or code number) and the source (name of the manufacturer) alternate materials of construction should be indicated postconsumer recycled plastic should not be used in the manufacture of a primary packaging component, and if it is used for a secondary or associated component, then the safety and compatibility of the material for its intended use should be addressed appropriately... 

The major category of compounds identified in the virgin and recycled HDPE is comprised of aliphatic hydrocarbons, such as pentadecane, hexade-cane, 1-hexadenene, branched alkanes, branched alkenes and others all oligomers of HDPE. Certain differences between virgin and recycled plastics are, however, obvious, e.g. carboxylic acids such as hexadecanoic and oc-tadecanoic acid were found only in the recycled HDPE. Only two ketones were identified, 6-dodecanone and 2-nodadecanone, in the recycled HDPE the former was also present in the virgin material. 

The first step in recycling plastics is to sort the plastics by their resin type, or resin identification code. The resin identification code is a number assigned to a plastic product (or container) according to the type of polymers it is made of. While it was once common to directly use this code to identify the types of polymer(s) present, there are now other methods, such as near-infrared spectroscopy or density sorting approaches, that are used to sort mass quantities of plastic samples for recycling. (See Polymer Chemistry for more information on resin identification codes.)... 

When discussing many subjects it is important that they be properly identified by definitions such is the case in recycling. Different definitions exist to meet different industry and commercial requirements. ASTM defines a recycled plastics as those plastics composed of postconsumer material and recovered material only, or both, that may or may not have been subjected to additional processing steps of the types used to make products such as recycled regrind, or processed or reconstituted plastics. The industry scrap includes what is commonly referred to as trim or regrind in plastic production, is not considered recycled material. 

Stambler, I., Plastic Identifiers Groomed to Cut Recycling Roadblocks, R D Magazine, October 1996, pp. 29-30. 

The plastics waste process helps to identify closed-loop structures and the process of recycling plastics waste does not run in just one direction, but an effect usually feeds back to change one or more of the causes , and that the causes themselves affect each other. It is an important part of the recycling process not to prioritise causes as being most or least important, but rather to understand how waste composition and quantity may change over time. 

These two major classifications of thermoplastics (TPs) and thermosets (TSs) in turn have different classifications such as virgin or recycled plastics. Virgin plastics have not been subjected to any fabricating process. NEAT plastics identify plastics with Nothing Else Added To. They are true virgin polymers since they do not contain additives, fillers, etc. However they are rarely used since they do not provide the best performances. Thus the technically correct term to identify the materials is plastics. Of the 35,000 types available worldwide there are about 200 basic types or famihes that are commercially recognized with less than 20 that are popularly used. Examples of these plastics are shown in Table 1.2. 

Often, PCA is used as an initial investigative technique to determine if any differences can be identified within a dataset prior to a separate classification or quantitative analysis. PC plots are similarly useful in these cases. The previously mentioned work on recyclable plastics by Allen et al. is one example of this approach. Another example is the PCA analysis of a set of ethylene-vinyl acetate copolymer samples by Shimoyama and coworkers who first identified measurable differences between Raman spectra before creating a quantitative model [45]. PCA was also used by Keen et al. to distinguish fibers for forensic applications [46]. 

At the beginning of this chapter, two major problems with recyclates were identified. The first, degradation, has been dealt with in previous sections. The second, the problem of dealing with mixed plastic wastes will now be addressed. 

Demand is increasing for additives which will render recycled plastics more easily reprocessable. The problem of identifying different plastics in a waste stream might also be solved by development of suitable tracer additives. 

The source of BP found in recycled food contact PET plastic needs to be identified, and more studies are needed to determine the scope and levels of UV-initiator contamination of recycled plastics. 

Recycling of unwanted polymers is the best solution, and six types of plastics in common use are frequently stamped with identifying codes assigned by the Society of the Plastics Industry (Table 31.2), After being sorted by type, the... 

DSM and Allied Signal have developed carpet identification equipment that can identify specific plastics. Particularly carpet made of nylon 6 (or nylon 66) fibres are separated, cut into pieces, isolated, and converted by polycondensation into their monomeric components. The monomers can then be reused in the production of nylon. DSM and Allied Signal opened the world s first large scale carpet recycling plant in Augusta, Georgia, US in November 1999. This plant has a capacity of 90,000 tpa nylon 6 carpet waste (109). 

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