Glass-fiber-reinforced thermoplastic polyester composites

T. F. Gray, Jr., Properties of a New Glass-Fiber Reinforced Thermoplastic Polyester , 26tA Annual Technical Conference, Reinforced Plastics/Composites Division, Society of the Plastics Industry, Inc., Washington, DC, 1971. 

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. 

Table 15.2 Selected properties of 30% glass-fiber-reinforced (GFR) thermoplastic polyester composites [15-17]...

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. 

Plueddemann et al. [ 20 ] introduced the term coupling agent , which characterizes its function in glass fiber reinforced polyester and epoxy laminates in 1962. Later, the applications of alkoxysilylpropyl- type silane coupling agents on particle-fiUed composite systems were applied to thermoplastics [21]. These had the structure... 

The most widely used and least expensive polymer resins are the polyesters and vinyl esters. These matrix materials are used primarily for glass fiber-reinforced composites. A large number of resin formulations provide a wide range of properties for these polymers. The epoxies are more expensive and, in addition to commercial applications, are also used extensively in PMCs for aerospace applications they have better mechanical properties and resistance to moisture than the polyesters and vinyl resins. For high-temperature applications, polyimide resins are employed their continuous-use, upper-temperature limit is approximately 230°C (450 F). Finally, high-temperature thermoplastic resins offer the potential to be used in future aerospace applications such materials include polyetheretherketone (PEEK), poly(phenylene sulfide) (PPS), and polyetherimide (PEI). 

The resin matrix can be either thermosetting or thermoplastic. Thermosetting resins such as epoxy, polyimide, polyester, and phenolic are used in applications where physical properties are important. Polyester and epoxy composites make up the bulk of the thermoset composite market. Of these two, polyesters dominate by far. Reinforced with glass fiber, these are known as fiberglass-reinforced plastics (FRPs). FRPs are molded by layup and spray-up methods or by compression molding either a preform or sheet molding compound (SMC). 

It is well accepted that the good properties of the isotactic polypropylene as an engineering polymer matrix in thermoplastic composite materials and engineering blends are seriously affected by the inability of this polymer to develop an adequate level of interfacial interaction with polar components such as mineral fillers (calcium carbonate) and reinforcements (talc, mica, wollastonite), synthetic reinforcements (glass fibers, carbon fibers, and nanotubes), or engineering polymers such as polyamide, aliphatic polyesters, and so on. 

A combination of carbon fiber, glass fiber or polyester fiber with phenolics leads to fiber reinforced phenolics that are called phenolic composites. Phenolic composites are interesting materials for the aircraft and aerospace industry because, in case of fire, they produce very low smoke density and low toxicity gases. Thermoplastic or elastomeric additives improve mechanical properties, adhesion and toughness of these composites but these additives cause a decrease in flame resistance [1,6],... 

Reinforced Plastic n (RP) A plastic composition in which are embedded fibers that are much stronger and typically much stifier than the matrix resin. The reinforcements are usually fibers, rovings, fabrics, or mats, or mixed forms of glass, carbon, asbestos, metals, ceramics, paper, sisal, cotton, or nylon. Resins most commonly used are polyesters, phenolics, aminos, siH-cones, epoxies, and various thermoplastics. The term reinforced plastic includes some forms of Laminate and molded parts in which the reinforcements are not in layered form. When the resin is thermoplastic, the term reinforced thermoplastic is often used. Methods of forming reinforced-plastics articles from thermosetting resins are defined under the entries Ksted below. 

These thermotropic liquid-crystalhne polymers have high melting points but can be melt-processed like other thermoplastics. The macroscopic orientation of the extended-chain crystals depends on the orientation imparted by flow during processing (molding, extrusion, etc.). Because of the fibrous nature of the extended-chain crystals, these plastics behave as self-reinforced composites, with excellent mechanical properties, at least in the chain direction. This is illustrated in Table 4.3 for molded specimens of a hquid-crystalline copolyester of ethylene glycol, terephthalic acid, and / -hydroxybenzoic acid [14]. In the direction parallel to the flow, the properties listed in Table 4.3 favorably compare with ordinary crystalline thermoplastics (nylons, polyesters) reinforced with up to 30% glass fibers. 

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