Polymers Dacron/poly

Naturally occurring polymers include proteins, nucleic acids, cellulose (polysaccharides), and rubber (polyisoprene). Most synthetic polymers are organic compounds. Familiar examples are nylon, poly(hexamethylene adipamide) Dacron, poly (ethylene terephthalate) and Lucite or Plexiglas, poly(methyl methacrylate). 

Poly(ethylene terephthalate), known by the trade names Mylar, Dacron, and Terylene, is a very high volume polymer—the United States production of PET fiber and plastic was over... 

A polyester is a polymer in which the polymerization forms an ester group. The repeating unit is an ester thus there are many esters, or "poly-esters." Dacron is an example. 

Both conventional and liquid-crystal polymers can be processed by melt spinning. The principal requirement is that the polymer must not degrade before becoming molten. Examples are nylon-6, nylon-6,6 and poly(ethylene terephthalate) ( polyester , terylene , or dacron ) for conventional polymers and the Vectra series (see section 12.4.3) among the thermotropic liquid-crystal polymers. 

The use of different polymers in contact with blood is shown in Table 4.3. It is clear that some polymers could be considered as blood-compatible when used in some conditions of flow but not in others. This is typically exemplified in the case of knitted or woven poly(ethylene terephthalate), e.g. Dacron , which can be used as a constituent of vascular prostheses in humans for replacing arteries larger than 6 mm in diameter but cannot be used for replacing smaller arteries and induces blood coagulation in static blood. 

Poly(ethylene terephthalate) (Dacron) proved to be the suitable material and even to this day remains the most used polymer for the purpose. The textile industrial already had techniques of seamless tubular weaving and these were readily applied to the manufacture of arterial grafts. However, the essential need for a strong. 

Condensation polymers are formed by the reaction of bifunctional or poly functional molecules, with the elimination of some small molecule (such as water, ammonia, or hydrogen chloride) as a by-product. Familiar examples of synthetic condensation polymers include polyesters (Dacron, Mylar), polyamides (nylon), polyurethanes, and epoxy resin. Natural condensation polymers include polyamino acids (protein), cellulose, and starch. The process can be represented as follows ... 

Polymers can also be classified in other ways for example, many varieties of rubber are often referred to as elastomers. Dacron is a fiber, and poly(vinyl acetate) is an adhesive. The addition and condensation classifications are used in this essay. 

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). 

An incredibly important issue in polymer chemistry is processing, the manner in which the crude polymer product is transformed into the final material used in applications. This is a topic best reserved for a chemical engineering textbook, but it should not be dismissed here, either. As an example, poly(ethylene terephthalate), which is considered the workhorse of the polyester industry, is used as both a fiber and a plaster under the trade names of Dacron and Mylar, respectively (look ahead to Figure 13.15 to see the structures). The processing procedure leads to the different properties and the ultimate applications. 

X-ray analysis reveals that poly(ethylene terephthalate) (Dacron ) belongs to the triclinic system (25). The cell dimensions are a = 4.56, b = 5.94, c = 10.75 A, with the angles being a= 98.5°, J5 = 118°, y= 112°. Both the polyamides and the aromatic polyesters are high melting polymers because of hydrogen bonding in the former case and chain stiffness in the latter case (see Table 6.1). As is well known, both of these polymers make excellent fibers and plastics. 

The popularity of clothing made of polyester-cotton blends testifies to the economic impact of this polymer. Poly (ethylene terephthalate) is the PETE referred to in the recycling codes listed in Table 27.1. Plastic bottles for juice, ketchup, and soft drinks are usually made of PETE, as is Mylar film and Dacron sails for boats. 

The strength of a fibre can be increased by drawing, this process being discussed in Section 2.4.4 and illustrated in Fig. 2.12. Common synthetic polymers used to produce fibres are generally polyamides, polyesters or polyacrylics. The class of nylons are the most familiar polyamides. For example, the structure of nylon-6,6 (here the numerals refer to the numbers of carbon atoms between successive amide groups in the repeating unit) is shown in Table 2.1. An example of a polyester is poly(ethylene terephthalate) (PET) (Table 2.1), known commercially in fabrics as tery-lene or dacron (this polymer is also used in PET plastic drink bottles). A well-known polyacrylic used to make fibres is poly(acrylonitrile) (Table 2.1). 

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