Glyptal, structure

C13-0122. Glyptal is a highly cross-linked polymer made by heating glycerol and phthalic anhydride. Show the structure of glyptal. 

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. ... 

The bulk of polyester production in the United States has gone to the synthetic coatings field in the manufacture of glyptal resin coatings and varnishes, with production between 200,000,000 and 300,000,000 pounds in the postwar years. A recent development has been the use of polyester-styrene copolymers reinforced by Fiberglas for the manufacture of items such as low-pressure molded boats, corrugated structural sheet, and plastic pipe. The 1947 requirements for glycerol in the production of polyester resins and... 

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. 

In the synthesis of Glyptal resin, two different kinds of small molecules have reacted to fom a unit that by repetition can build up an extended structure. 

In this experiment, the syntheses of two polyesters (Experiment 46A), nylon (Experiment 46B), and polystyrene (Experiment 46C) will be described. These polymers represent important commercial plastics. They also represent the main classes of polymers condensation (linear polyester, nylon), addition (polystyrene), and cross-linked (Glyptal polyester). Infrared spectroscopy is used in Experiment 46D to determine the structure of polymers. 

If more than two functional groups are present in one of the monomers, the polymer chains can be linked to one another (cross-linked) to form a three-dimensional network. Such structures are usually more rigid than linear structures and are useful in making paints and coatings. They may be classified as thermosetting plastics. The polyester Glyptal is prepared as follows ... 

The first truly synthetic polymer was a densely cross-linked material based on the reaction of phenol and formaldehyde see Section 14.2. The product, called Bakelite, was manufactured from 1910 onward for applications ranging from electrical appliances to phonograph records (16,17). Another early material was the General Electric Company s Glyptal, based on the condensation reaction of glycerol and phthalic anhydride (18), which followed shortly after Bakelite. However, very little was known about the actual chemical structure of these polymers until after Staudinger enunciated the Macromolecular Hypothesis in 1920. 

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