Poly plastics, disposal

Functional derivatives of polyethylene, particularly poly(vinyl alcohol) and poly(acryLic acid) and derivatives, have received attention because of their water-solubility and disposal iato the aqueous environment. Poly(vinyl alcohol) is used ia a wide variety of appHcations, including textiles, paper, plastic films, etc, and poly(acryLic acid) is widely used ia detergents as a builder, a super-absorbent for diapers and feminine hygiene products, for water treatment, ia thickeners, as pigment dispersant, etc (see Vinyl polymers, vinyl alcohol polymers). 

The quantity of these materials is relatively small compared with the amount of waste high-density poly(ethylene) produced each year. Containers made from HDPE are widely used for detergents, oil, and antifreeze, and enormous amounts of material are used in disposable applications aimually. In principle recycled poly(ethylene) could be used for drain pipes, flower pots, dustbins, and plastic crates. The problem remains, however, that economics do not favour recycling of these polymers and in the absence of Government intervention little or nothing can be done to alter commercial attitudes towards recycling. 

On land, too, there are changes in the way plastics are disposed of. In the UK some local authorities are actively promoting recycling of plastic bottles and poly(styrene) containers, for example by schemes where local residents place recyclable materials in designated boxes for refuse collectors. These boxes are taken to a Materials Reclamation Facility for final sorting of the plastics waste. 

About 10% of the ethylene produced in the U.S. is used to make vinyl chloride, which in the chemical trade is usually referred to as vinyl chloride monomer or VCM. The largest use of VCM is for polymerization to poly(vinyl chloride) (PVC), a thermoplastic, which in terms of volume is second only to polyethylene. PVC is used in such diverse areas as containers, floor coverings (linoleum), plastic pipes, raincoats, and many, many others. PVC has an evironmental disadvantage over non-chlorine containing plastics in that when it is disposed of by incineration it produces hydrogen chloride, which dissolves in atmospheric water to give hydrochloric acid. Polyethylene does not have this undesirable feature. 

Poly(ethylene terephthalate), PET, has become one of the major post-consumer plastic wastes. PET products do not present a direct threat to the environment, but they do pose a problem of considerable concern due to the huge amount of solid waste produced [1]. The disposal of this waste together with its low bio-degradability and photo-degradability, now represents a serious challenge for industrial countries worldwide. 

Commodity and engineering polymers. On the basis of end use and economic considerations, polymers can be divided into two major classes commodity plastics and engineering polymers. Commodity plastics are characterized by high volume and low cost. They are used frequently in the form of disposable items such as packaging film, but also find application in durable goods. Commodity plastics comprise principally of four major thermoplastic polymers polystyrene, polyethylene, polypropylene, and poly(vinyl chloride). 

An ideal way to recycle waste plastics is to remelt them and form new products directly, bnt this process is usually possible only in the case of rather homogeneous waste streams. With heterogeneous plastic-containing waste streams, however, because other processing steps would be required, landfilling and incineration are the most favored disposal methods from an economic point of view. These disposal processes can lead to environmental problems, especially in the case of halogen-containing plastics snch as poly (vinyl chloride) (PVC). 

Poly(butylene succinate) is currently used in fast-food packages, bottles, disposable plastic bags, mulch films and so on [85, 104, 105]. In these applications PBS is used as a homo... 

Plastic waste is already used in a similar capacity. Poly(urethane) scrap from the shoe manufacturing industries are shredded and used as filler in the manufacture of the soles of shoes [11]. However, as yet there are no reports of plans to extend this disposal option to cover post-consumer wastes. 

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