Fiber-reinforced unsaturated polyesters

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 ... 

The terms reinforced plastics (RP) and composites refer to combinations of plastic materials and reinforcing materials, usually in fiber form (chopped fibers, porous mats, woven fabrics, continuous fibers, etc. see Fig. 7-1). Both thermoset (TS) and thermoplastic (TP) resins are used. When modern RP industry started in 1940, glass-fiber-reinforced unsaturated polyester (TS), low pressure or contact pressure, curing resins were used. Today about 60 percent of the plastics industry uses many different forms of glass fiber-polyester composites. In this chapter the abbreviation RP will be used, and in references to polyester resin it will refer only to TS, as relatively little TP polyester is used in RPs. 

In cavity-compression molding the cold powder or mold material is placed under pressure in a heated mold. The process is also called hot pressing. Glass-fiber-reinforced, unsaturated polyester resins are processed by the heated-cavity-compression molding method. The vulcanization of rubber can also be carried out using this method. High-fidelity records are pressed out of the thermoplasts PVC or poly(ethylene-co-vinyl acetate), while cheaper records are injection molded. 

GF-UP Glass-fiber-reinforced unsaturated polyester resin... 

Figure 11-18. Fatigue strength under tensile stress (tensile strength) as a function of time for a glass-fiber-reinforced unsaturated polyester (UP), a high-impact-strength poly(styrene) (SAN), poly(styrene) (PS), and poly(ethylene) (PE) (after BASF).

Plastics, particularly polymer-based composites (both thermoplastic and thermoset composites), have been exploited in transportation appUcations for decades. The use of common composites such as glass or carbon fiber reinforced unsaturated polyesters, epoxy, and poly(vinyl ester) matrices is well known. The unique advantage of composites is their strength (tensile strength 4-6 times that of steel) and stiffness, despite their lightweight. 

Figure 13.1 Tensile strength of different surface-modified Grewia optiva particle fibers-reinforced unsaturated polyester composites.

Figure 13.5 Compressive strength of raw and AN-grafted particle fibers-reinforced unsaturated polyester composites [26]. Reprinted with permission from [26]. Copyright 2012 John WUey and Sons.

When reinforced with mercerized and benzoylated particle fibers. The UPE matrixhas been found to exhibit flexural strength of 55.26, 62.26, 66.29 and 57.26 MPa 61.7, 67.1, 69.52 and 62.32 MPa at 10,20,30 and 40% fiber loading, respectively. The results obtained were found to be consistent with results obtained in the case of AN graft copolymerized Grewia optiva fibers-reinforced unsaturated polyester composites [26]. Rai et al. have also reported similar results during their studies [16]. 

Figure 13.9 TGA curves for raw and surface-functionalized Grewia optiva fibers-reinforced unsaturated polyester matrix-based composites.

Singha, A.S., Rana, A.K., Jarial, R.K. Mechanical, dielectric and thermal properties of Grewia optiva fibers reinforced unsaturated polyester matrix based composites. Mater. Des. 51, 924-934 (2013)... 

Fillers like precipitated calcium carbonate might be used in a plastic composition to reduce the overall cost of the formulation or to improve its optical properties. With fillers such as carbon black (used in tire formulations) or glass fibers (used in fiber-reinforced unsaturated polyester, GRP), the primary role of the filler is to improve the mechanical properties of the composite. 

The use of fiber reinforced unsaturated polyester resin composites in the form of sheet molding compound (SMC), bulk molding compound (BMC) and preform molding exceeded 475 000 tons (approximately one billion pounds) in North America and Europe in 1995. Many applications were in the transportation industry such as automotive body panels, truck components and semi-structural parts (Table 1). Other applications are in sanitary ware (bathtubs, showers, sinks), applicances, business machines and electrical components. 

DIN 16869 [504] Parts 1 and 2 Centrifugally cast filled glass fiber reinforced unsaturated polyester resin (UP-GF) pipes,... 

The US Air Force was very interested in using glass fiber reinforced unsaturated polyester resins, but required even better humidity resistance, and so they funded research into better coupling agents. This research was quickly successful and led to silicon-based products that reduced the losses to less than 10% and resulted in the birth of fee organosilane coupling agent family, which still dominates the market more than 40 years from their first introduction. 

As described earlier, the use of organosilanes grew from work sponsored by the US Air Force to find products that performed better than the original chrome complexes in glass fiber reinforced unsaturated polyester resin composites. The first success was achieved with vinyl trichlorosilane and its mixtures with allyl alcohol. The unsaturation provided the polymer reactive functionality while the chloro-groups provided the fiber reactive ones. The fiber reactivity comes about by hydrolysis of the chloro-groups to form silicon hydroxyls, which are then able to condense with surface hydroxyls, as shown in the following simplified reaction sequence. 

Vilay, V., Mariatti, M., Taib, R.M., and Todo, M. (2008) Effect of fiber surface treatment and fiber loading on the properties of bagasse fiber-reinforced unsaturated polyester composites. Compos. Sci. Technol., 68, 631-638. 

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