Dacron preparation

A (a) What are polyesters (b) What is Dacron (c) How is Dacron prepared (d) What is Mylar (e) Is it reasonable to assume that a polyester can be made from propylene glycol and terephthalic acid If so, sketch its structure. 

Not all synthetic polymers are used as fibers Mylar for example is chemically the same as Dacron but IS prepared in the form of a thin film instead of a fiber Lexan is a polyester which because of its impact resistance is used as a shatterproof substitute for glass It IS a polycarbonate having the structure shown... 

In analogy to the transesterification of diethyl terephthalate used in the preparation of commercially important polyester fibers such as Dacron (24), a transesterification reaction waus successfully employed for the preparation of poly(N-acylhydroxyproline esters) (Scheme 1). 

Uses Preparation of terephthalic acid for polyester resins and fibers (Dacron, Mylar, Terylene), vitamins, pharmaceuticals, and insecticides. Major constituent in gasoline. 

Alcohols occur widely in nature. Methanol is also known as wood alcohol because it can be obtained by distilling wood in the absence of air. It is very poisonous and can cause blindness or death if ingested. Ethanol is consumed in alcoholic beverages. Other simple alcohols, such as 2-phenylethanol from roses and menthol from peppermint, are constituents of natural flavors and fragrances. Alcohols are important intermediates in chemical synthesis. They are also commonly used as solvents for various chemical processes. Ethylene glycol is used in antifreeze and in the preparation of polymers such as Dacron. 

Epoxides are important intermediates in many industrial processes. For example, the reaction of the simplest epoxide, ethylene oxide, with water is employed to produce ethylene glycol, which is used in antifreeze and to prepare polymers such as Dacron. One method for the preparation of ethylene oxide employs an intramolecular nucleophilic substitution reaction of ethylene chlorohydrin ... 

The first electrode for urea was prepared by immobilizing urease in a poly-acrylcimide gel on nylon or Dacron nets. The nets were placed onto a Beckman electrode (NH J selective) (59). In a later development, the electrode was improved by covering the enzyme gel layer with a cellophane membrane to prevent leaching of urease into the solution (60). The urease electrode could be used for 21 days with no loss of activity. 

Cotton is pure cellulose. Nylon is a polyamide and made by polymerizing adipic acid and hexamethylenediamine. The nylon polymer chain can be prepared with one acid and one amine group at the termini, or with both acids or both amines. Except for these terminal groups, there are no polar centers in nylon and consequently it is difficult to dye. Similarly Dacron, a polyester made by polymerizing ethylene glycol and terephthalic... 

Comparable results were obtained in formulations containing sodium silicate as a builder together with (M-5% sodium tripolyphosphate, using 250 ppm hard water and a bath temperature of 49°C (Illman, 1971). A nonionic surfactant prepared by polyoxyethylenation of a C12-15 alcohol mixture with 9-11 mol of ethylene oxide generally showed similar detergency to an anionic prepared by sulfation of a Ci2 i5 alcohol mixture previously polyoxyethylenated with 3 mol of ethylene oxide at all percentages of sodium tripolyphosphate, and both were considerably superior to a linear tridecylbenzenesulfonate and a sulfated C16-I8 alcohol mixture. The nonionic was somewhat better than the sulfated POE alcohol for removing nonpolar fatty soil from Dacron-cotton permapress, and the reverse was true for the removal of polar soil from Dacron-cotton permapress and carbon soil from cotton, but similar results for the two surfactants were obtained for clay removal from both Dacron-cotton permapress and cotton, and polar and nonpolar fatty soil from cotton. 

In this case, the urease is physically entrapped in a polyacrylamide matrix polymerized on the surface of an ammonium-ion glass electrode. The enzyme-gel matrix is supported on the electrode by a sheer dacron or nylon gauze, about the thickness of a nylon stocking, or it is held by a thin semipermeable cellophane sheet. The urea diffuses to the urease-gel membrane, where it is hydroly d to produce ammonium ion. Some of the ammonium ion diffuses through the thin membrane to the electrode surface, where it is monitored by the ammonium-sensitive electrode. The urea electrode is fairly stable, sensitive, specific for urea, has a usable lifetime of 2-3 weeks before a new gel layer must be prepared, and has a fairly fast response time ( < 120 sec). The output of the electrode is linear from about 10 to 10" M urea. 

The first urea electrode was prepared in 1969 by immobilizing urease in a polyacrylamide matrix on nylon or Dacron nets. These nets were then placed onto a glass cation-selective electrode. To improve the selectivity, an ammonium-ion selective electrode with... 

One of the best-known polymer condensation processes is the reaction between hexamethylenediamine and adipic acid, shown in Figure 25.6. The final product, called nylon 66 (because there are six carbon atoms each in hexamethylenediamine and adipic acid), was first made by Wallace Carothers at Du Pont in 1931. The versatility of nylons is so great that the annual production of nylons and related substances now amounts to several billion pounds. Figure 25.7 shows how nylon 66 is prepared in the laboratory. Condensation reactions are also used in the manufacture of Dacron (polyester)... 

Laminates can be prepared by either abrasion or the tear-ply technique. In the tear-ply design, the laminate is manufactured so that one ply of heavy fabric, such as Dacron, glass, or the equivalent, is attached at the bonding surface. Just prior to bonding, the tear-ply is stripped away, and a fresh, clean, hondable surface is exposed. 

Two foam insulation systems prepared by the A. D. Little Company of Cambridge, Massachusetts were also tested. These systems had two vapor barriers, one on the outer surface (Z/Z x and one at Z/Zj j x 0.62 (where Z is the distance into the insulation from the outer surface and Z the insulation thickness). Each vapor barrier was a laminate composed of one layer of mylar [0.013 mm (0.0005 in) thick], two layers of aluminum [0.025 mm and 0.013 mm (0.001 in and 0.0005 in) thick], another layer of mylar [0.013 mm (0.0005 in)], and a layer of dacron woven fabric [33.9 g/m (1.0 oz/yd )]. The two layers of mylar offer tensile strength, the two layers of aluminum resist gas diffusion, and the dacron cloth resists tearing. Both systems used foams which had chopped fiberglass added for reinforcement. One system used Sta-foam AA1602 (a toluenedi isocyanate), whereas the other used Upjohn 452 (a pol3nnetric isocyanate). As can be seen from Fig. 13b, both systems had fair thermal performance Initially, but the performance deteriorated rapidly with thermal cycles. 

Since the current prosthesis materials (Dacron and Teflon) are thrombogenic, our approach to solving the small diameter vascular prosthesis problem was to develop a blood compatible polymer. Much of these studies have been summarized in Reference 1. One of the polymers that we prepared which appeared to have a nonthrombogenic surface was a block copolyether-urethane-urea material. However, when this urethane material was fabricated into small diameter solid wall tubes and implanted in dogs, occlusion occurred within several days. Prostheses recovered from these experiments gave evidence that the thrombus was originating at the anastomosis between the artery and the prosthesis. We believed that a mismatch in compliance between the polymer and... 

Dacron, a polyester, can be prepared by causing a dicarboxylic acid to react with a bifunctional alcohol (a diol) ... 

This linear polyester is isomeric with Dacron, which is prepared from terephthalic acid and ethylene glycol (see the preceding essay). Dacron and the linear polyester made in this experiment are both thermoplastics. 

Polymers can also be prepared by a condensation approach where, for example, two monomer units are both bifunctional. In such cases a small molecule e.g., water) is eliminated at each reaction site and long polymer chains result. Adipic acid (5) and hexametliylenediamine (6) can be polymerised by the elimination of water to produce nylon (7). Nylon is an example of a polyamide and parallels the natural protein analogues. Polyesters (e.g., Dacron or Terylene, 10) are also prepared by a condensation... 

A useful polyester is prepared from terephthalic acid and ethylene glycol. More than 2 million tons of this polymer is produced annually in the United States. Dacron, the fiber produced from this polyester, accounts for approximately 50% of all synthetic fibers. It absorbs very little moisture, and its properties are nearly the same whether it is wet or dry. 

The history of thermoplastic polyester goes back to 1929 with the pioneering work of Carothers. The first aromatic polyester of importance is poly(ethylene terephthalate) commonly abbreviated PET (or PETE) and was prepared by Whinfield and Dickson. In 1941, they created the first polyester fibers called Terylene and first manufactured by Imperial Chemical Industries (ICI). PET was produced commercially in 1953 as fiber for textile industry (Dacron) by Dupont using modified nylon technology. Dupont polyester research rapidly leads to a whole range of trademarked products as Mylar, a strong polyester film. 

Polyethylene terephthalate (PET) is a synthetic polymer formed by the reaction of ethylene glycol (HOCH2CH2OH) and terephthalic acid. Because PET is lightweight and impervious to air and moisture, it is commonly used for transparent soft drink containers. PET is also used to produce synthetic fibers, sold under the trade name of Dacron. Of the six most common synthetic polymers, PET is the most easily recycled, in part because beverage bottles that bear the recycling code "1" are composed almost entirely of PET. Recycled polyethylene terephthalate is used for fleece clothing and carpeting. In Chapter 30, we learn about the preparation and properties of synthetic polymers like polyethylene terephthalate. 

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