Polyethylene terephthalate injection

Polyethylene terephthalate is injection blow molded to make water and carbonated drink bottles, and other liquid food packages. High stiffness, excellent clarity, and good resistance to carbon dioxide permeation are the principal attributes of these bottles. We carefully control molding conditions to promote transparency and surface gloss, which are prized for food... 

Polyesters, which are a class of engineering thermoplastics, are found in a wide variety of applications including carbonated drink bottles, fibers for synthetic fabrics, thin films for photographic films and food packaging, injection molded automotive parts, and housings for small appliances. In this chapter, we svill explore the synthesis of this class of polymers. We will also look at the typical properties and end uses for the most common of these resins, polyethylene terephthalate and polybutylene terephthalate, which are commonly known as PET and PBT, respectively. 

Polyethylene terephthalate is most often extruded into films or fibers, or blow molded into bottles. Polybutylene terephthalate is primarily found in injection molded parts. Such parts are highly crystalline, which makes them opaque. Polybutylene terephthalate is often modified with glass fibers or impact modifiers. Table 24.1 contains applications by processing method and resin. 

Injection molding grades of polyethylene terephthalate and polybutylene terephthalate have low melt viscosities. Because of this, they can be used to manufacture intricate parts within... 

Polyesters exhibit excellent high temperature strength and electrical properties making them a good choice for many demanding applications. They also are physiologically inert allowing them to be used in food contact applications. The two common polyesters, polyethylene terephthalate and polybutylene terephthalate, are both used in injection molded products. Polyethylene terephthalate is often used in both extrusion and blow molded processes also. 

Fakirov, S. and Fakirova, C., Direct determination of the orientation of short glass fibers in an injection-molded polyethylene terephthalate) system, Polym. Composites, 6, 41 (1985). 

Fig. 6.8. Fracture toughness, K, of short glass fiber-thermoplastics injection molded composites as a function of weight fraction of fiber, fVr. (O) and (A) polyethylene terephthalate (PET) matrix ( ) and (A) polycarbonate (PC) matrix. Notches made transverse (O, ) and parallel (A, A) to the mold fill direction,...

By far the most important plastic is polyethylene terephthalate (PET). Bottles of this material are formed in a two-stage process. So-called pre-forms are made by injection moulding and, in a second process, are then stretch-blow-moulded to produce a bottle. PET has properties surprisingly like those of glass, but it does not have the same disadvantages of weight and brittleness. 

Alpha Packaging manufactures botdes and jars made from polyethylene terephthalate (PET) and high-density polyethylene (HDPE) for the pharmaceutical, nutritional and personal care markets. Technologies used include injection blow moulding, injection stretch blow moulding, and extrusion blow moulding. Alpha manufactures stock and custom containers in a variety of styles and colours. 

Thennoset polyesters, such as Glyptal, alkyds and glass reinforced unsaturated polyesters have been available for several decades but Injection moldable polyaryl esters are relatively new. Whinfield and Dickerson extruded polyethylene terephthalate (PET) fibers (Dacron) in the 194O s. ( )pET was also extruded as film (Mylar) in the 1950 s but this polymer was not blow molded commercially until the 1970 s. 

In the usual space-charge limited theory, electrons are injected into the insulator conduction band, and some of these electrons are immobilized in localized defect states. We have considered an alternate mechanism more appropriate to the polymer structure. Contact charge transfer studies in Polyethylene Terephthalate (PET) and other polymers (15-16) suggest that the electronic states accessible from metal contacts are localized molecular-ion states located deep in the forbidden energy gap. Charge transport is by hopping between localized states. 

Plastics make up only about 8 percent of the volume in the average landfill but represent a huge investment of energy and raw materials. Most plastics produced from petroleum materials by polymerization of monomers such as ethylene or vinyl chloride are thermoplastic materials and can be cleaned, melted, and re-formed. Thermosetting plastics can also be cut into pieces that are mixed with other plastics or used as fillers. High-density polyethylene (HDPE) and polyethylene terephthalate (PETE) are the most widely reused plastic materials, but polyvinyl chloride (PVC), polypropylene, and polystyrene account for 5 percent of the recycled plastics. In 2001 80 million pounds (36 milfion kilograms) of plastics were recycled in the United States. Recycled plastic materials are used in the production of bottles, fabrics, flowerpots, furniture, plastic lumber, injection molded crates, and automobile parts. 

Photovoltaic effects in polymers have continued to attract interest. Polyethylene films sandwiched between parallel transparent electrodes exhibit photocurrent pulses on illumination after being subjected to d.c. fields of up to 105 V mm-1 the effect is attributed to a hopping motion of detrapped electrons in the field of an injected space-charge.156 Similar studies have been carried out on polyethylene terephthalate),157 other organic polymers,168 and polymer- 158 ... 

If the materials are anisotropic, they will present different properties in the different directions. Examples of these polymeric materials are polymer fibers, such as polyethylene terephthalate, PET, nylon fibers, injection-molded polymers, fiber-reinforced composites with a polymeric matrix, and crystalline polymers where the crystalline phase is not randomly oriented. A typical method for measuring the modulus in tension is the stress-strain test, in which the modulus corresponds to the initial slope of the stress-strain curve. Figure 21.4 shows typical stress-strain curves for different types of polymeric materials. 

The process can combine conventional glass fiber roving, aramid, or carbon fiber tows with TPs, most commonly polyethylene terephthalate (PET) and nylon (polyamide/PA). Other plastics used include polyphenylene sulphide (PPS), styrene-maleic anhydride (SMA), high-density polyethylene (HDPE), and polypropylene (PP). The TPs can take the form of pellets, chips, chunks, or shreds, and as the process uses hot-melt injection, no solvents or two-part systems are involved. Additives such as colorants and fillers can be used as required. 

Multilayer injection blow-molded containers have been available for a much shorter time than multilayer extrusion blow-molded containers, as development of the process was more difficult. However, these too are now available. A prominent example is multilayer polyethylene terephthalate (PET)-based ketchup bottles, which contain three layers of PET, and two layers of ethylene vinyl alcohol (EVOH) as an oxygen barrier. 

Polyethylene Terephthalate. Crystallization is difficult and slow. Particularly for injection molding, 0.5 percent of 3- im metal oxide, metal salt, pigment, or other minerals, and ionomer are mentioned. For thermo formed food trays, 1 to 3 percent of low-MW polyolefin. 

Polyethylene terephthalate (PET, polyethylene glycol terephthalate) n. A saturated, thermoplastic polyester resin made by condensing ethylene glycol, and terephthalic acid, used for textile fibers, water-clear, biaxially oriented film (e.g., Mylar ) and, more recently, for extruded, thermoform-able sheet (TV-dinner trays), injection-molded parts, and large, blow-molded, soft-drink bottles. It is extremely hard, wear- and chemical-resistant, dimensionally stable, and has good dielectric properties. See also polyester, saturated and crystallized polyethylene terephthalate (See image). 

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