Dacron, structure

Fischer projections of, 980 Dacron, structure of, 819 Danishefsky, Samuel, 1002 Darzens reaction. 913 DCC (dicyclohexylcarbodiimide),... 

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... 

Draw the structure of the polymer you would expect to obtain from reaction of dimethyl lerephthalate with a triol such as glycerol. What structural feature would this new polymer have that was not present in Dacron How do you think this new feature might affect the properties of the polymer ... 

Fibers are thin threads produced by extruding a molten polymer through small holes in a die, or spinneret. The fibers are then cooled and drawn out, which orients the crystallite regions along the axis of the fiber and adds considerable tensile strength (Figure 31.3). Nylon, Dacron, and polyethylene all have the semicrystalline structure necessary for drawing into oriented fibers. 

I) Buna-S (II) Buna-N (III) Dacron (Iv) Neoprene Identify the monomer In the following pol5mierIc structures. 

Problem 16.56 Indicate the reactions involved and show the structures of the following condensation polymers obtained from the indicated reactants (a) Nylon 66 from adipic acid and hexamethylene diamine (b) Nylon 6 from e-caprolactam (c) Dacron from methyl terephthalate and ethylene glycol (d) Glyptal from glycerol and terephthalic acid (e) polyurethane from diisocyanates and ethylene glycol. ... 

Chemically, Dacron and Mylar are polymers made from a ring structure called dimethyl terephthalate and ethylene glycol (HO-CH2CH2-OH). The polymer unit is called polyethylene terephthalate, or PET. Dacron fiber is used in tires and fabrics, and is even used to repair blood vessels. Mylar is used in magnetic recording tape. In the 1960s, it was used in huge balloons that were sent into orbit around Earth. Plastic soda containers are made of PET. 

Polyester fibers, similar to polyamide fibers, represent another important family of fiber. Polyester fiber was discovered in England in 1941 and commercialized in 1950. Two common trade names of polyester are Dacron in the US and Terylene in the UK. The term polyester fiber represents a family of fibers made of polyethylene terephthalate. Dimethyl terephthalate is reacted with ethylene glycol in the presence of a catalyst, antimony oxide, to produce polyethylene terephthalate or polyester. The chain repeat structure of PET is given in Fig. 4.6. Although polyesters can be both thermosetting and thermoplastic, the term polyester has become synonymous with PET. Note that the PET chain structure is different from the simpler structure of nylon or polyethylene. In PET, the aromatic ring and its associated C-C bonds provide a rigidity to the structure. The polyester structure is also bulkier than that of nylon or polyethylene. These factors make polyester less flexible than nylon and polyethylene, and the crystallization rate of PET slower than that of nylon or polyethylene. Thus, when polyester is cooled from the melt, an appreciable amount of crystallization does not result. 

If each monomer molecule contains just two functional groups, growth can occur in only two directions, and a linear polymer is obtained, as in nylon 66 or Dacron. But if reaction can occur at more than two positions in a monomer, there is formed a highly cross-linked space network polymer, as in Glyptal, an alkyd resin. Dacron and Glyptal are both polyesters, but their structures are quite different and, as we shall see, so are their uses. 

When a polymer is made, monomers bond together one after another in a rapid series of steps. A catalyst usually is required for the reaction to take place at a reasonable pace. With some polymers, such as Dacron and nylon, two or more kinds of monomers bond to each other in an alternating sequence. A reaction in which monomer units are bonded together to form a polymer is called a polymerization reaction. The repeating group of atoms formed by the bonding of the monomers is called the structural unit of the polymer. The structural unit of a polymer made from two different monomers has the components of both monomers. 

Dacron pressed paper was found to be highly adequate for permeate transport while possessing the wet strength plastic properties needed in winding operations. Dacron paper was also used in casting membranes directly on support structures. 

Write a balanced equation for the reaction between 1,4-benzenedicarboxylic acid and 1,2-dihydroxyethane to form the polyester Dacron. Draw an abbreviated structure for the polymer, with brackets around the repeat unit. 

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