Glass fiber reinforced thermosets properties

TABLE 15.20 Topical Properties of Glass-Fiber-Reinforced Thermoset Polyesters... 

Unsaturated polyesters with molecular weights of several thousand are made commercially by condensing maleic anhydride or phthalic anhydride with ethylene glycol or propylene glycol. The subsequent free radical copolymerization with 30-35% by wt styrene leads to a cross-linked product which possesses exceptionally good mechanical properties, particularly when reinforced with glass fiber. The thermosetting properties... 

Thermosets usually provide higher mechanical and thermal properties at a lower material cost than do thermoplastics, more bang for the buck so to speak. However, most of the processes used to fabricate thermoset parts are slower and more limited in design freedom than the thermoplastic processes. Furthermore, the opportunity to utilize 100% of the material which thermoplastics provide is simply not available with thermosets because the regrind cannot be reused. Recycling possibilities are far more limited for thermosets for the same reason. Nonetheless, glass fiber-reinforced thermoset polyester is the material of choice for many outdoor applications in a severe environment such as boats and truck housings. 

TABLE 5.50 Typical Physical Properties of Glass-Fiber-Reinforced Thermosetting Resin Pipe ... 

Kaolin is primarily used in the rubber industry as a filler and is frequently used in the calcined form. It is being widely used in innerliner compound in the tubeless tire industry. Use of kaolin in glass fiber reinforced thermosets improves surface quality, reduces warpage, and lowers crack formation. Kaolin is used in polyvinyl chloride (PVC) wire coating because of its good electrical insulating properties. Surface-treated calcined kaolines are used for tire wheel cap made from polyamides (PA) and greenhouse films from LDPE [7[. 

Some of the common types of plastics that ate used ate thermoplastics, such as poly(phenylene sulfide) (PPS) (see Polymers containing sulfur), nylons, Hquid crystal polymer (LCP), the polyesters (qv) such as polyesters that ate 30% glass-fiber reinforced, and poly(ethylene terephthalate) (PET), and polyetherimide (PEI) and thermosets such as diaHyl phthalate and phenoHc resins (qv). Because of the wide variety of manufacturing processes and usage requirements, these materials ate available in several variations which have a range of physical properties. 

As mentioned earlier, suspensions of particulate rods or fibers are almost always non-Brownian. Such fiber suspensions are important precursors to composite materials that use fiber inclusions as mechanical reinforcement agents or as modifiers of thermal, electrical, or dielectrical properties. A common example is that of glass-fiber-reinforced composites, in which the matrix is a thermoplastic or a thermosetting polymer (Darlington et al. 1977). Fiber suspensions are also important in the pulp and paper industry. These materials are often molded, cast, or coated in the liquid suspension state, and the flow properties of the suspension are therefore relevant to the final composite properties. Especially important is the distribution of fiber orientations, which controls transport properties in the composite. There have been many experimental and theoretical studies of the flow properties of fibrous suspensions, which have been reviewed by Ganani and Powell (1985) and by Zimsak et al. (1994). 

Such glass fiber-reinforced composites based on the unsaturated polyester thermosets are usually fabricated as sheet molding compounds (SMC) and bulk molding compounds (BMC). These are widely used in various metal replacement applications because of their cost-effectiveness, rigidity, light weight, and corrosion resistance properties particularly useful in transportation (cars and trucks), constmction, pipe, and tank applications. Automotive and tmck body panel and strucmral component applications of SMC include doors, hatchbacks, hoods, front grilles, etc. Some nonautomotive applications of SMC and BMC include sanitaryware (bathtubs, shower stalls, sinks), appliances, business machine, and electrical components. 

Finishes on reinforcing fibers notably improve the inherent dry strength of the composite, but often they are used to retain physical properties after exposure to a wet environment. Finishes generally can be formulated to work with both thermoplastic and thermosetting resins and various types of glass fiber reinforcements. 

Hidemitsu Hojo et al. (Hidemitsu et al., 1998) reviewed the behavior, the forms and mechanisms of corrosion of resins and glass fiber reinforced plastics under several aqueous solutions. They concluded that the concept of the corrosion rate of metals could be applied even in plastics and fiber reinforced plastics for each corrosion form. The corrosion resistance of the composites is mainly dependant on the resin s corrosion resistance properties and the corrosion crack propagation. Applications requiring corrosion resistant composite materials usually use epoxy and polyester resin as the composite matrix because these thermosets have high resistance to chemical attack. Among the various type of resins epoxies dominate the... 

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