Poly ethylene terephthalate bottles

Much of the success of the poly(ethylene terephthalate) bottle has arisen from the control of the biaxial orientation that occurs during manufacture to give a product both strong and of low gas permeability. 

Franz R, Huber M, Piringer O G, Damant A P, Jickells S M and Castle L, 1996, Study of Functional Barrier Properties of Multilayer Recycled Poly(ethylene terephthalate) Bottles for Soft Drinks. J. Agric. Food Chem. 44, 892-897. 

R. FRANZ, M. HUBER, O. G. PIRINGER, A. P. DAMANT, S. M. JICKELLS, L. CASTLE, Study of functional barrier properties of multilayer recycled poly(ethylene terephthalate) bottles for soft drinks. Journal of Agricultural and Food Chemistry, 1996, 44, 892-897. 

Acetaldehyde content of freshly blown poly(ethylene terephthalate) bottles ASTM D4509... 

Vinylidene Chloride Copolymer Latex. Vinylidene chloride copolymers can be made in emulsion, and then isolated, dried, and used as coating or extrusion resins. Stable latices have been prepared and can be used directly for coatings (225-230). The principal applications for these materials are as barrier coatings on paper products and, more recently, on plastic films. The heat-seal characteristics of VDC copolymer coatings are equally valuable in many applications. They are also used for paints and as binders for non woven fabrics (231). Special VDC copolymer latices are used for barrier laminating adhesives, and the use of VDC copolymers in flame-resistant carpet backing is well known (232-235). VDC latices can also be used to coat poly(ethylene terephthalate) bottles to retain carbon dioxide (236). 

In 1954 the surface fluorination of polyethylene sheets by using a soHd CO2 cooled heat sink was patented (44). Later patents covered the fluorination of PVC (45) and polyethylene bottles (46). Studies of surface fluorination of polymer films have been reported (47). The fluorination of polyethylene powder was described (48) as a fiery intense reaction, which was finally controlled by dilution with an inert gas at reduced pressures. Direct fluorination of polymers was achieved in 1970 (8,49). More recently, surface fluorinations of poly(vinyl fluoride), polycarbonates, polystyrene, and poly(methyl methacrylate), and the surface fluorination of containers have been described (50,51). Partially fluorinated poly(ethylene terephthalate) and polyamides such as nylon have excellent soil release properties as well as high wettabiUty (52,53). The most advanced direct fluorination technology in the area of single-compound synthesis and synthesis of high performance fluids is currently practiced by 3M Co. of St. Paul, Minnesota, and by Exfluor Research Corp. of Austin, Texas. 

Soft-drink bottles made from poly(ethylene terephthalate) (PET) are usuady made by stretch-blow mol ding in a two-step process. Eirst, a test-tube-shaped preform is molded, which is then reheated to just above its glass-transition temperature, stretched, and blown. Stretching the PET produces biaxial orientation, which improves transparency, strength, and toughness of the botde (54,56). A one-step process is used for many custom containers that are injection stretch-blow molded. 

Two often used polymers have adequate properties for some appHcations. Poly(ethylene terephthalate) (PET) is used to make films and bottles. 

Poly(ethylene terephthalate) (PET) bottles have been used for some time as an alternative to glass and aluminum. At first one-way bottles ia different sizes were used returnable PET-botfles of reasonable quaUty have been marketed. In the future, returnable PET-botfles will be used. The first examples of total production lines have been exhibited, ie, blow-form-fill-seal ia an extra superblock constmction. 

In the late 1970s several developments occurred causing renewed interest in poly(ethylene terephthalate) as a plastics material. These included the development of a new mouldable grade by ICI (Melinar) and the development of a blow moulding technique to produce biaxially oriented PET bottles. In addition there appeared a glass-fibre filled, ionomer nucleated, dibenzoate plasticised material by Du Pont (Rynite) (see Chapter 26). 

With the expiry of the basic ICI patents on poly(ethylene terephthalate) there was considerable development in terephthalate polymers in the early 1970s. More than a dozen companies introduced poly(butylene terephthalate) as an engineering plastics material whilst a polyether-ester thermoplastic rubber was introduced by Du Pont as Hytrel. Polyfethylene terephthalate) was also the basis of the glass-filled engineering polymer (Rynite) introduced by Du Pont in the late 1970s. Towards the end of the 1970s poly(ethylene terephthalate) was used for the manufacture of biaxially oriented bottles for beer, colas and other carbonated drinks, and this application has since become of major importance. Similar processes are now used for making wide-neck Jars. 

Poly(ethylene terephthalate) (PET) is one of the most extensively recycled polymeric materials. In 1995, 3.5 x 104 tons of PET were recycled in Europe.1 The main reason for the widespread recycling of PET is its extensive use in plastic packaging applications, especially in the beverage industry as plastic bottles. The consistency in terms of volume and availability of postconsumer bottles from sorting facilities and its high material scrap value create an excellent economic environment for PET recycling. 

Poly(ethylene terephthalate) Drinks bottles, oven-ready tray meals ... 

In America there are promising signs for certain polymers. For example, poly(ethylene terephthalate) drinks bottles can be cleaned and recycled to give an acceptable grade of PET resin in a process that is economically viable. The recycled polymer is used as carpet fibre, furniture stuffing, or insulation. Waste nylon can also be recycled profitably. 

Stretching a polymer in two perpendicular directions, either successively or by blowing a bubble of molten material, leads to its biaxial orientation, which strongly improves mechanical properties in the stretching directions and/or gas permeability (e.g., biaxial orientation of polypropylene leads to BOPP (for biaxially oriented polypropylene) or biaxial orientation of poly(ethylene terephthalate) gives CC>2-impermeable bottles for carbonated beverages.) (Characterisation methods for determining molecular orientation are considered in Chapter 8.)... 

Polyesters and polyamides are the most prevalent of this type of polymer. Poly(ethylene terephthalate) is used in bottle manufacture and along with other packaging plastics is not biodegradable. Potts(54) established very early that only low melting and low molecular weight aliphatic polyesters were biodegradable. 

Table 9.5 lists the uses of ethylene oxide. Ethylene glycol is eventually used in two primary types of end products polyesters and antifreeze. About half the ethylene glycol is used for each end product. Poly(ethylene terephthalate) is the leading synthetic fiber and has other important applications in plastic film and bottles. Ethylene glycol is a common antifreezing agent especially in automobile radiators. 

Table 11.6 shows the uses of TA/DMT. TA or DMT is usually reacted with ethylene glycol to give poly(ethylene terephthalate) (90%) but sometimes it is combined with 1,4-butanediol to yield poly(butylene terephthalate). Polyester fibers are used in the textile industry. Films find applications as magnetic tapes, electrical insulation, photographic film, and packaging. Polyester bottles, especially in the soft drink market, are growing rapidly in demand. 

Polyacrylonitrile plastic bottles for soft drinks and beer were taken off the market as possible carcinogens because of migration of acrylonitrile into the drink. Now most plastic food containers of this type are poly(ethylene terephthalate). 

In the past few years many changes have occurred in the packaging materials utilized for distilled spirits. Traditionally, distilled spirits have been packed primarily in glass containers of approved ATF sizes. Over the last 5—10 years, plastic containers, primarily poly(ethylene terephthalate) (PET), have been utilized by increasing numbers of distillers. Because of environmental concerns, the last two years have seen a change back to glass on some of these package sizes. However, the 50 ml, miniature bottle continues to be primarily packed in PET plastic containers. 

The superior properties of polypropylene terephthalate) (PPT) polymer and fibers over the chemically analogous poly(ethylene terephthalate) (PET, used for soda bottles) and poly(butylene terephthalate) (PBT) have been well known for several decades PPT fibers are much more elastic and less brittle than PET and offer better recovery from stretching than PBT they are also easier to dye than either PET or PBT. Compared to the intermediate for PET, ethylene glycol, which is available inexpensively from ethylene oxide, and to that for PBT, butanediol, likewise available inexpensively from butene or butadiene, the intermediate for PPT, 1,3 propanediol (1,3-PPD or PDO), was not - and on a large scale is still not - available. Three processes, two chemical ones and one biotechnological, compete to change this situation (Figure 20.10). 

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