Other Saturated Polyesters

The third, and fastest growing, area of isophthahc acid use is in other types of polymers, primarily as a minor comonomer with terephthahc acid in saturated polyesters. Over 20% of the isophthahc acid is sold in this apphcation. One rapidly expanding use is in polyester beverage bottles where addition of up to 3% isophthahc acid to the terephthahc acid allows faster production of more complex shapes. In this way, single piece bottles can be made, vs a round-bottomed bottle that needs a separate base cup. Fibers are also modified with isophthahc acid. 

Saturated polyesters and saturated alkyds cannot undergo such modification with vinyl monomers but can be modified with other polymers such as silicone resins by alcoholysis. Here outdoor durability is considerably improved. 

Low profile plastics are added to reduce shrinkage during cure. They are normally thermoplastics that include polyvinyl acetates, polymethyl methacrylate, and copolymers with other acrylate, vinyl chloride-vinyl acetate copolymers, polyurethane, polystyrene, polycaprolactone, cellulose acetate butyrate, saturated polyester, and styrene butadiene copolymers. More details about the low profile additive (LPA) mechanism are published in the literature. ... 

Polyester resins are condensation products of di- or polyfunctional monomers containing hydroxyl groups and carboxyl groups. The development of saturated polyesters began in 1901 with Glyptal resins , formed from glycerol and phthalic anhydride (Smith, United States). Soluble resins obtained with fatty acids were first employed in 1925. Alkyd resins formed from unsaturated fatty acids can be cured by atmospheric oxidation (see Section 2,6). Other unsaturated polyester resins are discussed in Section 2.8. 

The subsequent development of saturated polyester resins for paints and other uses (e.g., adhesives, foams, fibers) was largely dependent on the introduction of new raw materials. A broad range of raw materials are now available, examples follow ... 

Saturated polyester-resins have been defined in Chapter 12 and their use with nitrogen resins was described in Chapter 13. The resins used in polyurethane finishes might contain a selection from the ingredients listed on p. 161 and, amongst others ... 

The unsaturated polyester coatings of the type earlier described are nowadays mostly replaced with other resin types of lower viscosity. Instead of an unsaturated polyester resin, lower molecular weight polymers may be used, often called acrylic oligomers. These oligomers are for example the reaction products of acrylic acid and end groups in epoxy resins (epoxy acrylates) and in saturated polyesters (polyester acrylates). The linking reactions are shown diagrammatically ... 

The tendeney of polyolefins to undergo oxidative degradation decreases in the order PP LDPE HDPE. The polyamides, polyurethanes, the saturated polyesters (PET, PBT), certain other engineering thermoplastics and many rubbers are also susceptible to various extents. 

Polyester resins are polycondensates prepared in two different forms saturated and unsaturated. Saturated polyesters, alkyd resins, are produced from dicarbox-ylic acids and polyalcohols. Dicarboxylic acids, chiefly phthalic acid or maleic acid, are mainly used in their anhydride forms. Glycerol, pentaerythriol or trimeth-ylolpropane are the most-used polyalcohols. The saturated polyesters synthesized in this way are also named unmodified alkyd resins, which are macromolecules commonly used as plasticizers for other plastic materials. Alkyd resins can be modified by oil-containing fatty acids to be used in water-based paints and surface coatings (Bjorkner 1992 Kanerva et al. i996a,b Tarvainen 1996). 

Ramis and co-workers (48) made a similar study of SINs prepared from im-saturated polyester-styrene mixes with MDI-poly(propylene glycol). When the storage modulus, E, was plotted through a range of compositions, the Budiansky equation (47) was again found to fit better than several other relationships. 

Resin production is performed in production plants that may be integrated in larger facilities or that are completely standalone units. In some cases, UPES resins are produced in multipurpose plants where other resins, like alkyds and saturated polyesters, are also produced. The market demands a large variety of resins in order to suit the wide variety of end market applications and conversion technologies applied. This is reflected in the resin production facilities being able to produce a variety of products on the basis of different raw materials (recipes), process conditions and to target final specifications. Order size and packaging demand (bulk, container, and drum) add to the complexity of the production facility. 

Because of their lesser ability to control shrinkage, the non-polar polymers such as polystyrene and polyethylene are often classified as low shrink rather than low profile additives. Usually, low profile additives are supplied as 30-40% polymer solutions in styrene monomer. Polyester resin manufacturers also package the low profile additives dissolved in their resins. These are referred to as one pack systems. As the industry has expanded, other thermoplastics have been identified which have shrinkage control properties. These are also now used commercially in a variety of applications. Examples of these other polyers are saturated polyesters, polyurethanes, stryene-butadiene copolymers and polycapro-lactones. Polyfvinyl acetate) based materials are probably still the most used low profile additives, being useful with the broadest range of unsaturated polyester resin structures. Relative proportions of the organics used in most formulations are 30-50% polyester alkyd, 10-20% thermoplastic and 40-50% styrene. 

Thermoset materials can be made from phenolic resins themselves, requiring an acid or base catalyst or additional formaldehyde source, or in combination with various other resins. An exhaustive list is not given here, but examples of combinations with all the resin types in the next sections are known (especially amino resins. Section 16.3 epoxy resins. Section 16.4 alkyd resins, Section 16.5 and saturated polyester resins. Section 16.6). 

History. The most sophisticated work on saturated polyesters is usually traced to W. H. Carothers, who, from 1928 to 1935 with DuPont, studied polyhydroxy condensates of carbolic acids. Unable to achieve suitable heat and chemical resistance from these esters, he turned to polyamide-carboxylic acid reaction products, which later became nylon. Carothers concepts on saturated polyesters yielded several other polyester products such as Terylene, which became patented and introduced in the United States as dacron and mylar. 

PHB (Figure 13.1) is linear saturated polyester, fuUy biodegradable behaving like a thermoplastic polymer [4,6]. It is insoluble in water and soluble in some nonpolar solvents such as chloroform, dichloro-methane and dimethylformamide it is also a semicrystalline material with a high content of crystallinity and high production cost due to its low production rates when compared to other conventional polymers [7,8]. 

Polyesters, such as microbially produced poly[(P)-3-hydroxybutyric acid] [poly(3HB)], other poly[(P)-hydroxyalkanoic acids] [poly(HA)] and related biosynthetic or chemosynthetic polyesters are a class of polymers that have potential applications as thermoplastic elastomers. In contrast to poly(ethylene) and similar polymers with saturated, non-functionalized carbon backbones, poly(HA) can be biodegraded to water, methane, and/or carbon dioxide. This review provides an overview of the microbiology, biochemistry and molecular biology of poly(HA) biodegradation. In particular, the properties of extracellular and intracellular poly(HA) hydrolyzing enzymes [poly(HA) depolymerases] are described. 

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