Polyethylene terephthalate consumption

Polyesters, The healthiest trend coming out of the plastics industry— personal health, that is—is the ubiquitous PET water bottle. Medical doctors all agree that the increased daily consumption of water enhances well-being. The improvement in producing PET, polyethylene terephthalate, in the 1970s, led to this pervasive replacement of glass bottles because of the cost and portability. 

The most important representatives of this group are polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). The consumption of PET in the world (excluding fibers) was about 4x 106 t in 1997 (audio and video films, technical mouldings, packaging, particularly bottles). Even though the cost of these plastics is presently in the medium price range, one can count on a reduction in their price in the future due to their widespread use. 

Plastics and rubber are essential materials in today s industrialized societies. The consumption of plastics has grown by a factor of about 60 in the past 30 years, which has led to a corresponding increase in the generation of plastic wastes. One of the most valuable properties of plastics, their low density, is one of the major limitations in the recycling of plastic wastes. Thus, to recover one tonne of plastics it is necessary to collect about 20 000 plastic bottles. Plastic wastes are mainly found in municipal solid wastes (MSW). As a consequence of their low density, plastics account for just 8 wt% of the MSW, but this value increases to over 20% in volume terms. In spite of the great diversity of plastic materials, plastic wastes are made up of a relatively small number of polymers polyethylene, polypropylene, polystyrene, polyvinyl chloride and polyethylene terephthalate. These resins account for more than 90% of total plastic wastes. 

Consumption of virgin polyethylene terephthalate (PET) resin in the United States and Canada totaled 5110 million pounds in 2000 [3]. Bottles were by far the largest application (Fig. 4.8). Soft drink bottles continue to be the largest use for PET bottles, but other applications (custom bottles) have been growing at a much faster rate for the past several years. According to EPA estimates, soft drink bottles accounted for 49.4% of all PET packaging in U.S. municipal solid waste in 1998, and 53.2% of all PET containers in municipal solid waste [1]. 

The production and applications of polymers have gradually developed, gaining ground in many fields. The main classes of polymers, namely polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene and polyethylene terephthalate are produced in millions of tonnes annually [1]. There are many methods of polymer synthesis free-radical polymerisation (bulk, solution, emulsion and suspension), condensation polymerisation, ethoxylation, polymer compounding and formulations involving solvents, fillers, pigments and so on. Besides the high volume consumption of these common plastics, the demand for polymers with specific end-use properties has increased. 

Poly(lactic acid) (PLA) is a thermoplastic polyester characterized by mechanical and optical properties similar to polystyrene (PS) and polyethylene terephthalate (PET). It is obtained from natural sources, completely biodegradable and compostable in controlled conditions as already stated in previous chapters. PLA offers some key points with respect to classic synthetic polymers, since it is a bioresource and renewable, while raw materials are cheap and abundant compared to oil. From a commercial point of view, a non-secondaiy approach, it can embellish with the word green so fashioned for the major stream consumers. Legislation can also help the commercial diffusion of biopolymers. As an example, a decisive leap has been made with the control of non-biodegradable shopping bags distribution in the European Commission and many of its member states. In addition, PLA has received some interest from the industrial sectors because of its relatively low price and commercial availability compared with other bioplastics. This is the veiy key point for any successful polymer application. In fact, the current price of commercial PLA falls between 1.5 and 2 kg , which is sufficiently close to other polymers like polyolefins, polyesters or poly(vinyl chloride) (PVC). Clearly, the PLA market is still in its infancy, but it is expected that the decrease in the production costs and the improvement in product performance will result in a clear acceleration in the industrial interest for PLA uses. It is estimated that PLA consumption should reach... 

Amongst the polymers based on crude oil, seven groups of polymers - polyolefins (PE and PP), polystyrene (PS), polyvinyl chloride (PVC), polyethylene terephthalate (PET), emulsion polymerised styrene butadiene rubber (ESBR), polyamides (PA) and unsaturated polyester resins (UP) constitute approximately 80 % of the total consumption of polymers. 

The development of flexible printed wiring was made possible through the availability of plastic films that possess high electrical insulation and good chemical resistance, in particular polyethylene terephthalate and polyimide films which account for over 95% of the flexible film consumption for printed wiring applications. The properties of the most important of these polymers are discussed in the following sections. 

Polyethylene terephthalate (PET) (Scheme 5.1) is a linear thermoplastic polyester with excellent mechanical, chemical and physical properties, and optical clarity, which is widely used in multiple applications such as food packaging, soft-drink bottles, photographic films, audio tapes, video tapes, fibres and fihn-moulding materials. Currently, the overall world consumption of PET amounts to about 13 million tonnes. In view of such a large consumption, the effective utilisation of PET waste is of considerable commercial and technological significance. 

China is currently the world s largest producer and consumer of polyester fibres (for textile use). According to government statistics, China s consumption of purified terephthalic acid (PTA), the primary raw material used in the manufacture of polyester fibres, and polyethylene terephthalate (PET), for bottles, textiles, packaging and film products. 

Fig. 16. U.S. plastic materials consumption for thin-gauge (2.1 million metric tons) and heavy-gauge (682,000 t) thermoforming (32). PE = Polyethylene ABS = acrylonitrile-butadiene-styrene PS = polystyrene PP = polyproplyene PMMA = poly(methyl methylacrylate) PVC = poly(vinyl Chloride) PET = poly(ethylene terephthalate). Redrawn and used with permission of SPE Thermoforming Division.

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