Unsaturated polyester resin Application

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 ... 

The applications of the unsaturated polyester resins were increased in the late 1960s by the introduction of water-extended polyesters. In these materials water is dispersed into the resin in very tiny droplets (ca 2-5 p.m diameter). Up to 90% of the system can consist of water but more commonly about equal parts of resin and water are used. The water component has two basic virtues in this system it is very cheap and because of its high specific heat it is a good heat sink for moderating cure exotherms and also giving good heat shielding properties of interest in ablation studies. 

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). 

Osaka Organic Chemical will embark on volume production of a low-toxicity acrylic ester monomer with extremely low skin irritation, it is briefly reported. Principal applications are as a diluent monomer for UV and EB coating materials and inks, and as a modifier in unsaturated polyester resins, acrylic resins and PVC. OSAKA ORGANIC CHEMICAL INDUSTRIES CO.LTD. 

Moreover, y-P.V.19 is also found in a variety of other media, such as powder coatings and cast resins. This includes systems based on unsaturated polyester resins whose hardening is not affected by the pigment. The list of application media includes plastics which are processed at very high temperature (such as polycarbonates), in which the pigment is thermally stable up to 320°C. PUR foams and... 

Finally, glass-reinforced unsaturated polyesters are well known as building materials for boats, yachts and cars and generally termed fibre-glass resin . The preparation, properties and applications of these unsaturated polyesters are summarized in Chapter 21, while the chemistry and properties of a new unsaturated polyester resin for fibre-reinforced composite materials are discussed in Chapter 22. 

Table 21.2 provides a general guide to the effect that chemical constituents can have on unsaturated polyester resin end-use performance. The routes to change an unsaturated polyester resin for a particular application is normally apparent and there can be several pathways available to achieve the desired properties. As the unsaturated polyester resin markets are highly competitive, raw material cost usually reduces the number of available routes available to the formulator. As noted previously, there are three main types or families of unsaturated polyesters, namely general purpose orthophthalic, isophthalic and DCPD resins. However, within each of these families, there are hundreds of variants that incorporate these various chemical constituents in different combinations and permutations to achieve the desired results. 

Since unsaturated polyester resins alone would have insufficient strength for structural application, reinforcements are used to enhance the physical strength of such resins. Typically, tensile strength, impact strength and stiffness are the physical properties of most interest. Reinforcements can be regular particulates, as in glass microspheres, irregular particulates, as in flakes, or fibers. 

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. 

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. 

Construction applications for unsaturated polyesters resins can be sub-divide into four significant segments, as follows ... 

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. 

There are perhaps hundreds of miscellaneous unsaturated polyester resin construction applications. These would include window frames, doors, cabinet enclosures, electrical boxes, etc. In addition, recent developments bode well for unsaturated polyesters in construction markets. Concrete rebar, bridge construction and general infrastructure repair are examples of growing construction applications. 

Transportation applications include exterior automotive body components, non-appearance automotive parts, structural components, plus numerous truck, bus and rail car applications. Unsaturated polyester resins compete on the basis of weight reduction, corrosion resistance and parts consolidation. Thermoplastic resins, however, offer steep competition. 

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. 

In the transportation industry, there is an ever increasing use in auto, truck and bus applications. The advent of the electric vehicle, which may demand vastly improved weight reduction over today s state-of-the-art vehicles, would be a natural extension of current unsaturated polyester resin technologies. 

From an industrial point of view, not only the high-molecular-weight linear polyesters are of interest. Also, a series of low-molecular-weight linear or branched polyesters (Example 4-1) find application in surface coating systems (alkyd resins), as coreactants in unsaturated polyester resins (Example 4-8), or in polyurethane foams (Examples 5-28 and 5-29). 

Maleic anhydride itself has lew. if any. consumer uses bul its derivatives are of significant commercial interesi. The majority of Ihc maleic-anhydride produced is used in unsaturated polyester resin tsee Polyesters. L nsaturated). Unsaiuratcd polyester resin is then used in both glass-reinforced applications and unreinlorced applications. 

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. 

Another important application is the introduction of a thermoplastic such as poly(vinyl acetate), PVAc, into an unsaturated polyester resin to improve dimensional stability of the mold part. Keeping in mind (sec. 2.3.2) that an unsaturated polyester is dissolved in styrene, the modifier is the third component and the behavior is described with the help of a ternary-phase diagram (Fig. 8.3, Suspene et al., 1991). 

For commodity applications, there are four major classes of resins that are used in FRP applications. They are phenolic resin, epoxy resin, unsaturated polyester resin, and epoxy vinyl ester resins. A more complete description of these types of resins and their many variations can be found in Handbook of Thermoset Plastics. This is not a comprehensive list of resins used in composite manufacture, as commodity materials like polyurethanes and isocyanurate resins are sometimes used as well to make FRP parts. However, these materials are not covered in this chapter owing to their limited use, but, the principals of fire safety that apply for the resins described subsequently apply to these materials as well. 

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