Applications of Unsaturated Polyester Resins

As discussed previously, there are thousands of unsaturated polyester resins based on the available chemical constituents. However, major application areas require specific performance and the unsaturated polyester resins used can be broadly categorized by the major chemical constituents that deliver the specific performance necessary. Table 21.5 contains such a categorization. This should be used as a general reference because discrete, end-product performance may dictate a departure from these general categorizations. 

Gel-coat resins are a particular class of unsaturated polyester resins. Gel coats provide finish appearance to the unsaturated polyester parts and may also provide 

Marine Powerboats, sailboats, canoes, kayaks, personal watercraft 

Construction Bathtubs, shower stalls, hot tubs, spas, cultured marble, building panels, swimming pools, floor grating, doors, electrical boxes and cabinets, countertops, sinks, tanks, pipes, pipe linings, concrete rebar, bridges, concrete forming pans 

Transportation Body panels, under the hood components, truck cabs, tractor components, structural elements 

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In coatings, one of the main applications of unsaturated polyester resins is in furniture and wood finishes. They are also used in gel coats for boats and bathroom fixtures. Another important area of application is in automotive fillers and putties. Unsaturated polyesters are also widely used in chemical resistant coatings and linings for chemical and petrochemical storage tanks. 

World production of unsaturated polyester resins in 1997 was of the order of 1.7 X 10 tonnes, with the USA accounting for about 45% and Western Europe 27%. Over 75% is used in reinforced plastics, with the rest being used for such diverse applications as car repair putties, cultured marble , wood substitution and surface coatings. The pattern of consumption in 1993 of reinforced polyesters in the USA was reported as ... 

Polyester resins. The fire-performance characteristics of unsaturated polyester resins are of utmost importance in many application areas, particularly in the construction, transportation and electronics industries ( 1 3). Consequently, these plastics represent one of the major growth areas for fire retardants in recent years ( 1 4). 

Consumption of unsaturated polyesters in the marine industry consists of broad usage for hulls, decks and numerous small parts such as hatch and engine covers. Hulls and decks are generally produced with unsaturated polyester resins and multiple layers of fiberglass cloth knits and chopped fibers. Most marine applications require the use of unsaturated polyester resin gel coats for exterior appearance and for protection from the elements. 

The driving forces for the establishment of unsaturated polyester resin pipe, tank and fittings applications were environmental regulations, on-site labor savings and corrosion resistance. 

Sheet molding compounds (SMCs) and bulk molding compounds (BMCs) are the dominant materials used in automotive applications. These composites of unsaturated polyester resin, fillers and fiberglass have advantages of high stiffness, heat resistance and low coefficient of expansion. Coupled with low creep resistance, which is a distinct advantage over thermoplastic competition, and low-profile additives, which can yield Class A surfaces, these materials are well suited for applications from exterior body panels to under the hood components. 

Diacyl peroxides are used in a broad spectmm of applications, including curing of unsaturated polyester resin compositions, cross-linking of elastomers, production of poly(vinyl chloride), polystyrene, and polyacrylates, and in many nonpolymeric addition reactions. 

Polymer concretes show excellent mechanical properties and chemical resistance compared with conventional cement concretes. Polymer concretes can be cured quickly by the use of curing agents. Thus, the applications of polymer concretes are being increased. One of the popular polymers for polymer concretes is unsaturated polyester (UPE) resin. The properties of UPE resin can be modified by changing its molecular features. For the synthesis of the resin, phthalic anhydride or isophthalic acid as well as maleic anhydride can be employed to modify the mechanical properties or hydrothermal resistance. Terephthalic acid which is also used for the synthesis of poly ethylene terephthalate (PET) enhances the thermal resistance of the cured UPE resin. However, the synthesis of unsaturated polyester resin from terephthalic acid is difficult. One method to synthesize unsaturated polyester from terephthalic acid is the use of recycled PET. 

Polyurethane products and formulated systems are used in rigid foams, flexible foams, adhesives, sealants, coatings and elastomers, as well as in many other applications. Propene glycols are used in a wide variety of end-use and industrial applications, from unsaturated polyester resins, cosmetics and household detergents, to paints and automotive brake fluids. Propene glycol ethers are commonly... 

Here, in particular, reinforced plastics like GF-UP (molding material of glass-fiber reinforced, unsaturated polyester resin) and SMC (laminar semifinished parts of glass fabric, fillers and unsaturated polyester resin) are concerned, as used in car and ship building. For these applications, suitable repair sets on the basis of unsaturated polyester resins are available that enable repair according to the following procedure ... 

A wide range of chemical agents, catalysts and conditions for the glycolysis of unsaturated polyester resins, used in the manufacture of buttons, have been described in a recent patent.34 In addition to different metal acetates, the following compounds have been proposed to be catalytically active in PET glycolysis sodium methylate, sodium ethylate, sodium hydroxide, methane-sulfonic acid, magnesium oxide, barium oxide and calcium oxide. Different applications of the depolymerization products were described, e.g., preparation of fresh unsaturated polyesters by reaction with maleic acid, maleic acid/ phthalic anhydride or maleic anhydride/terephthalic acid or the synthesis of polyurethane resins by reaction with a diisocyanate. 

Tetrabromophthalic anhydride. Flame retardant in production of unsaturated polyester resins and rigid PU polyols co-hardener for epoxy resins cost efficient additive for latex emulsions derivatives used as flame retardants in diverse applications (wire coating, and wool, etc.). Crystals mp = 279-281 insoluble in H2O. Ethyl Corp. Great Lakes Firm Chem. 

Table 21.5 Types of unsaturated polyester resins employed in major applications...

The Sprut-5M adhesive consists of unsaturated polyester resin 100 parts hy weight, ATG-M 80 parts (a mixture of 50 parts of macrodiisocyanate md 30 parts of ATG), polymerization initiator (MEKP(O)) 2 parts. Usually lwt% of CN is integrated additionally into the adhesive base. Sprut-5M can be produced using various polyester resins, but the most applicable one is the adhesive based on PM-I resin owing to its availability and low cost. For this reason we will consider the properties of the adhesive based mainly on this resin although it has adhesion strength 20—40% lower than that of adhesives based on PN-11, NPS 609-21M, and other resins, especially when cementing in water. 

A more convenient method is not to decrease the elastic modulus of the whole adhesive but to form an elastic finish coat [182] not less than 30 pm thick [183] on the adhesive—substrate interface. With lower elastic modulus, the mobility of structural elements decreases. Application of an elastic sublayer decreased the internal stresses during the formation of coatings made of unsaturated polyester resins [185], epoxides [186], and polymer solutions [187]. The use of elastic finish coats found comparatively wide application for paint coatings but seems less promising for adhesive-bonded joints because of decrease of the adhesion strength due to the low cohesion strength of the finish coat itself and because of the labor requirements in producing the adhesive-bonded joints. 

If one works at higher temperatures, then the butadiene preferentially polymerizes at the 1,2 position. The vinyl groups thus produced can subsequently be cross-linked. Thus, the product has about the same field of application as unsaturated polyester resins, but it is less sensitive to weathering, because of the absence of heteroatoms. 

Xylitol is a specialty chemical with the effects of extreme cooling, caries prevention and safety for diabetes, which are beneficial for manufacturing foods and mouth-care products. As a platform chemical, it also can be converted to various compounds for polymer synthesis and directly polymerized for production of unsaturated polyester resin (Werpy and Petersen, 2004). Danisco (currently part of Dupont Co.) is the largest xylitol producer, and many companies in China and South America (Brazil) manufacture xylitol commercially. The global market of xylitol is estimated to be more than 125,000 tons per year, with 4.5-5.5/kg for bulk purchase and 20/kg in supermarket (da Silva and Chandel, 2012). Xylitol has a 12% share of the total polyols market with growth estimated to increase threefold (da Silva and Chandel, 2012). The xylitol market continues to increase worldwide due to an enhancement in health consciousness and chewing gum market, and new application development as a chemical feedstock. 

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