Polyester finishes

Unsaturated polyester finishes of this type do not need to be stoved to effect crosslinking, but will cure at room temperature once a suitable peroxide initiator cobalt salt activator are added. The system then has a finite pot life and needs to be applied soon after mixing. Such a system is an example of a two-pack system. That is the finish is supplied in two packages to be mixed shortly before use, with obvious limitations. However, polymerisation can also be induced by ultra violet radiation or electron beam exposure when polymerisation occurs almost instantaneously. These techniques are used widely in packaging, particularly cans, for which many other unsaturated polymers, such as unsaturated acrylic resins have been devised. 

Figure 8. Polyester finished paper showing differences between manufacturing...

Esterases In development polyester finish, removal of oligomers... 

Figure 4 Example of planar projection of the minimal energy configuration of a ternary system composed of a cellulose I schematic elementary crystallite surface, the photopol5mierizable acrylic primer tripropyleneglycol diacrylate (TPGDA), and a polyester finish. (From Refs. 72, 73.)...

Polyester finishes contain polyester resins, which, in turn, contain predominantly ester linkages. Polyurethane finishes need not contain polyurethane resins and the urethane linkage is not necessarily predominant in the dry paint film. However, all polyurethane finishes contain isocyanates or their reaction products, so the reader should be familiar with isocyanate reactions before proceeding further with this chapter. 

Polyester finishes are very hard, tough, resistant to solvents and resistant to moderately hot objects (e.g. a teapot or a lighted cigarette). These are extremely useful properties for a furniture finish, clear or pigmented. 

The polyester finished should be thinned 12 1 by volume (varnish thinner) with a 20 per cent solution of dibutyl phthalate in methanol. 

High-quality one-package polyester finishes are used on furniture, appliances, automobiles, magnet wire, and industrial products. Polyester powder coatings are used as high-quality finishes in indoor and outdoor applications for anything from tables to trucks. They are also used as coil coatings. 

Fig. 16.1 The cross-linking of an unsaturated polyester finish. The broken rods symbolize portions of the polyester chains and the dashes represent styrene molecules.

Adhesives based on methyl methacrylate and epoxy resins are used by engine-fitter mechanics (Castelain et al. 1992). In this way, they can come into contact with DGEBA, TGPAP, TGMDA, and epoxy novolac. Painters can work with products containing cyclohexanone peroxide, a catalyst for polyester finish. The standard allergens to consider are listed in Table 2 additional allergens in the aircraft industry are listed in Table 3. 

Cyclohexanone peroxide 0.5% (catalyst for polyester finish) (Rietschel and Fowler 1995)... 

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