PET See: Polyesters

Polyester sheet products may be produced from amorphous poly(ethylene terephalate) (PET) or partiaHy crystallized PET. Acid-modified (PETA) and glycol modified (PETG) resins are used to make ultraclear sheet for packaging. Poly(butylene terephthalate) (PBT) has also been used in sheet form. Liquid-crystal polyester resins are recent entries into the market for specialty sheet. They exhibit great strength, dimensional stabHity, and inertness at temperatures above 250°C (see Polyesters,thermoplastic). 

Polyester. Poly(ethylene terephthalate) [25038-59-9] (PET) polyester film has intermediate gas- and water- vapor barrier properties, very high tensile and impact strengths, and high temperature resistance (see Polyesters, thermoplastic). AppHcations include use as an outer web in laminations to protect aluminum foil. It is coated with PVDC to function as the flat or sealing web for vacuum/gas flush packaged processed meat, cheese, or fresh pasta. 

Recycled poly(ethylene terephthalate) (PET), which offers excellent properties at potentially lower cost, is finding wider use as a raw material component and meeting increasing demands for environmentally compatible resins (see POLYESTERS,THERMOPLASTIC Recycling, PLASTICS). 

Polyester Fibers Containing Phosphorus. Numerous patents describe poly(ethylene terephthalate) (PET) flame retarded with phosphorus-containing difimctional reactants. At least two of these appear to be commercial (see Polyesters, Fibers). 

The main area of interest for plasticizers in PET is in the area of dyeing. Because of its lack of hydrogen bonds, PET is relatively difficult to dye. Plasticizers used in this process can increase the speed and intensity of the dyeing process. The compounds used, however, tend to be of low molecular weight since high volatility is required to enable rapid removal of plasticizer from the product (see POLYESTERS, Thermoplastic). 

The principal applications of PEN and PEN/PET blends and copolymers are as films (see Polyester Films). 

PEN-based fibers extend the performance of polyesters. PEN fibers have excellent heat resistance, modulus, and dimensional stability relative to PET and demonstrate better retention of mechanical properties in a hot/wet environment and offer improved chemical resistance versus PET fibers (see Polyesters, Fibers). With naphthalate modification, polyester fibers can meet the application requirements, which are currently served by other high performance industrial fibers such as rayon, nylon-6,6, aramids, poly(phenylene sulfide) (PPS), and even steel. 

Whinfield and W. Dickson, working at the Calico Printers Association (2,3). Other polymers pioneered by these workers included poly(l,3-propylene terephthalate), 3GT, poly(l,4-butylene terephthalate), 4GT, and the polyester from ethylene glycol and l,2-6is(4-carbox5 henoxy)ethane, known as CPE-2G or Fiber-0 (4). Of these materials, PET was selected for development as a melt-spinnable synthetic fiber, but commercialization was impossible until after the end of World War II. Eventually, when the various national economies were back on a peacetime footing, PET polymer and fibers derived from it were put into production. The whole market-driving force for polyester at this time was in the form of synthetic fibers. In the United Kingdom, the new material was manufactured by Imperial Chemical Industries Ltd. imder the trade name Terylene, while DuPont introduced it to the United States in 1953 as Dacron (see Polyesters, Fibers). 

Standard polyester fibers contain no reactive dye sites. PET fibers are typically dyed by diffusiag dispersed dyestuffs iato the amorphous regions ia the fibers. Copolyesters from a variety of copolymeri2able glycol or diacid comonomers open the fiber stmcture to achieve deep dyeabiHty (7,28—30). This approach is useful when the attendant effects on the copolyester thermal or physical properties are not of concern (31,32). The addition of anionic sites to polyester usiag sodium dimethyl 5-sulfoisophthalate [3965-55-7] has been practiced to make fibers receptive to cationic dyes (33). Yams and fabrics made from mixtures of disperse and cationicaHy dyeable PET show a visual range from subde heather tones to striking contrasts (see Dyes, application and evaluation). 

Polyesters are also used in continuous filament spunbonded nonwovens (see Nonwoven fabrics). Reemay spunbonded fabric is composed of continuous filament PET with a polyester copolymer binder. These spunbonded fabrics are available in a wide range of thicknesses and basis weights and can be used for electrical insulation, coated fabric substrates, disposable apparel for clean rooms, hospitals, and geotextiles (qv). 

Noncrystalline aromatic polycarbonates (qv) and polyesters (polyarylates) and alloys of polycarbonate with other thermoplastics are considered elsewhere, as are aHphatic polyesters derived from natural or biological sources such as poly(3-hydroxybutyrate), poly(glycoHde), or poly(lactide) these, too, are separately covered (see Polymers, environmentally degradable Sutures). Thermoplastic elastomers derived from poly(ester—ether) block copolymers such as PBT/PTMEG-T [82662-36-0] and known by commercial names such as Hytrel and Riteflex are included here in the section on poly(butylene terephthalate). Specific polymers are dealt with largely in order of volume, which puts PET first by virtue of its enormous market volume in bottie resin. 

Some of the common types of plastics that ate used ate thermoplastics, such as poly(phenylene sulfide) (PPS) (see Polymers containing sulfur), nylons, Hquid crystal polymer (LCP), the polyesters (qv) such as polyesters that ate 30% glass-fiber reinforced, and poly(ethylene terephthalate) (PET), and polyetherimide (PEI) and thermosets such as diaHyl phthalate and phenoHc resins (qv). Because of the wide variety of manufacturing processes and usage requirements, these materials ate available in several variations which have a range of physical properties. 

Most polyesters (qv) are based on phthalates. They are referred to as aromatic-aHphatic or aromatic according to the copolymerized diol. Thus poly(ethylene terephthalate) [25038-59-9] (PET), poly(butyelene terephthalate) [24968-12-5] (PBT), and related polymers are termed aromatic-aHphatic polyester resins, whereas poly(bisphenol A phthalate)s are called aromatic polyester resins or polyarylates PET and PBT resins are the largest volume aromatic-aHphatic products. Other aromatic-aHphatic polyesters (65) include Eastman Kodak s Kodar resin, which is a PET resin modified with isophthalate and dimethylolcyclohexane. Polyarylate resins are lower volume specialty resins for high temperature (HDT) end uses (see HeaT-RESISTANT POLYAffiRS). 

This class of polyesters consists of four major commercial polymers and their copolymers, namely PET, PTT, PBT, and PEN (see Table 2.1). They compete for engineering thermoplastics, films, and fibers markets with other semicrystalline polymers, such as aliphatic polyamides, and for some other applications with amorphous engineering plastics such as polycarbonate. The syntheses of PET and PBT, detailed in numerous reviews and books,2-5 are described in Sections 23.2.2 and 2.3.2.1. 

Aromatic carboxylic dianhydride chain extenders (e.g. PMDA) are a low-cost way of converting recycled PET flakes into high-IV crystalline pellets that can be used in high-value applications (e.g. bottles, strapping, foam, engineering alloys/compounds, etc.) (see Figure 14.2). PMDA is an effective chain extension additive for thermoplastic polyesters such as PET and PBT. It is suitable for the following applications ... 

Solid-state polycondensation of thermoplastic polyesters such as PET is therefore both time-consuming and energy-intensive. Recently, additives have been developed to accelerate this process [23, 24], Such additives enable PET with a very high IV to be produced at reduced residence times in the solid-state reactor, with enhanced outputs and at a reduced cost. Such additives accelerate the IV enhancement of PET at low cost. One such SSP accelerator is Irgamod 1425 which when used in PET at levels of between 0.1-0.5wt% gives an SSP acceleration of approximately 50 % (see Figure 14.5). 

The two main brominated flame retardants used commercially in PET are PyroChek 68PB (see Figure 14.18) and Saytex HP-7010 (Albemarle). Both of these flame retardants are based on brominated polystyrene. While there are similarities between these flame retardants, they are not equivalents. There are quality and performance differences between these two products as they use different raw materials (i.e. polystyrenes) and the process for bromination is different. Saytex HP-7010 has better thermal stability and colour control than does PyroCheck 68 PB. However, if higher flow characteristics are a necessary property of the FR-PET, then Pyrocheck 68 PB would be the product of choice. Sodium antimonate is the appropriate synergist in PET since it is more stable at the higher processing temperatures required of PET and does not cause depolymerization of this polyesters. 

The workhorse polyester is polyethylene terephthalate) (PET) which is used for packaging, stretch-blown bottles and for the production of fibre for textile products. The mechanism, catalysis and kinetics of PET polymerization are described in Chapter 2. Newer polymerization techniques involving the ring-opening of cyclic polyester oligomers is providing another route to the production of commercial thermoplastic polyesters (see Chapter 3). 

Polyester is the Madison Avenue name for PET, polyethylene terephtha-late. Be careful, though, because PET is not a polyethylene-type chemical— its a xylene derivative. If you remember that esters usually end in -ate and are based on the acid from which they are derived, then you can see that the ester in polyester is ethylene terephthalate. 

Over the past several decades, there has been a continuing growth in the worldwide demand for plastics, films and fibers, particularly polyesters. The raw materials that make up these polymers are based primarily on the C8 family of aromatics (C8A)-ethylbenzene (EB), para-xylene (PX), meta-xylene (MX), and ortho-xylene (OX). Polyester (PET plastic), derived from PX, in particular has experienced rapid growth and is projected to see continue rapid growth as many developing countries desire to have the lifestyle flexibility that such readily available, versatile plastics support. While the markets for MX- and OX-derived plastics are smaller (plasticizers and specialty polyesters, respectively), all C8A markets continue to increase with population growth [59],... 

---