Continuous fibers polyester

Naturally occurring fibers such as cotton, cellulose, etc., have short whiskers protruding from the surface, which help to give a physical bond when mixed with rubber. Glass, nylon, polyester, and rayon have smooth surfaces and adhesion of these fibers to the rubber matrix is comparatively poor. In addition, these synthetic fibers have chemically unreactive surfaces, which must be treated to enable a bond to form with the mbber. In general, the fibers are dipped in adhesives in the latex form and this technology is the most common one used for continuous fibers. The adhesion between elastomers and fibers was discussed by Kubo [128]. Hisaki et al. [129] and Kubo [130] proposed a... 

We will see in Section 5.4.2 that the elastic modulus of a unidirectional, continuous-fiber-reinforced composite depends on whether the composite is tested along the direction of fiber orientation (parallel) or normal to the fiber direction (transverse). In fact, the elastic modulus parallel to the fibers, Ei, is given by Eq. (1.62), whereas the transverse modulus, 2, is given by Eq. (1.63). Consider a composite material that consists of 40% (by volume) continuous, uniaxially aligned, glass fibers (Ef =16 GPa) in a polyester matrix (Em = 3 GPa). 

Blends of polyesterand cellulosic fibers are printed with disperse and reactive dyes only in cases, when pigment printing is unsatisfactory. Dye selection follows basically the rules given for continuous dyeing polyester and cellulose fibers. 

Organic matrices are divided into thermosets and thermoplastics. The main thermoset matrices are polyesters, epoxies, phenolics, and polyimides, polyesters being the most widely used in commercial applications (3,4). Epoxy and polyimide resins are applied in advanced composites for structural aerospace applications (1,5). Thermoplastics Uke polyolefins, nylons, and polyesters are reinforced with short fibers (3). They are known as traditional polymeric matrices. Advanced thermoplastic polymeric matrices like poly(ether ketones) and polysulfones have a higher service temperature than the traditional ones (1,6). They have service properties similar to those of thermoset matrices and are reinforced with continuous fibers. Of course, composites reinforced with discontinuous fibers have weaker mechanical properties than those with continuous fibers. Elastomers are generally reinforced by the addition of carbon black or silica. Although they are reinforced polymers, traditionally they are studied separately due to their singular properties (see Chap. 3). 

Equations such as Equation 3.144 give satisfactory agreement with the measured values of strength and modulus for polyester composites reinforced with chopped strands of glass fibers. These strength and modulus values are only about 20%-25% of those achieved by reinforcement with continuous fibers. 

The workhorse of the RTS industry is TS polyester (also called polyester-TS) with glass fiber. The fiber reinforcement may be in the form of chopped fibers, porous nonwoven mats, woven fabrics, or continuous fibers. The combination of plastics and reinforcements results in versatile materials with unusual characteristics. The reinforcement adds strength and toughness to inherent weather resistance, moldability, and colorability. Thus RTSs are used because of their increased tensile, flexural, torsional, and impact strengths increased modulus of elasticity increased creep resistance reduced coefficient of thermal expansion increased thermal conductivity and, in many cases, lower costs. 

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 contrast to extrusion, in pultrusion a combination of liquid resin and continuous fibers is pulled continuously through a heated die of the shape required for continuous profiles. Shapes Include structural I-beams, L-channels, tubes, angles, rods, sheets, and so on, and the resins most commonly used are polyesters with fillers. Other resins such as epoxies and urethanes are used where their properties are needed. Longitudinal fibers are generally continuous rovings. Glass fiber material (mat or woven) is added for cross-ply properties. 

Hand Lay-uplSpray up Spray up and open contact molding (hand lay-up) in one-sided molds is one of the cheapest and most common process for making fiber composite products. Typical products are boat hulls and decks, truck cabs and fenders. In a typical open mold application, the mold is first waxed and sprayed with gel coat and cured in a heated oven at about 49°C. In the spray up process, after the gel coat is cured, catalyzed resin (usually polyester or vinyl ester at 500-1,000 cP viscosity) is sprayed into the mold, along with chopped fiber. A secondary spray up layer imbeds the core between the laminates (sandwich construction). Then it is cured, cooled, and removed from the reusable mold. In hand layup processing, continuous fiber strand mat and other fabrics such as woven roving are manually placed in the mold. Each ply is sprayed with catalyzed resin (1,000-1,500 cP) and the resin is worked into the fiber with brush rollers to wet-out and compact the laminate. 

Pultrusion is a modern technique used for producing continuous fiber-reinforced profile in which the orientation of the fiber is kept constant during cure. Although this process is utilized for both thermoplastic and thermoset resins, it is mainly suitable for thermosetting resins like polyester, epoxy and phenolic resin systems. Jute, available in continuous forms such as mat, roving, tapes, yarn, etc., is impregnated with... 

In filament winding the continuous fibers are impregnated in a resin mix bath and then woxmd on a rotating mandrel. The successful cylinders with longitudinal or helical and hoop reinforcement were made with sisal epoxy and jute-polyester. 

Pultrusion. in pultmsion a combination of liquid resin and continuous fiber is pulled continuously through a heated die of the required shape for continuous profiles, such as structural channel, angles, rods, and sheets (1). The plastic sides and top of stepladders are common examples of pultrusion. Commonly employed resins are polyesters, epoxies, and polyurethanes. A typical process might be 3-5 min in duration where resin temperatures ramp rapidly from ambient to temperatures in excess of 150°C, hold for a short time, and ramp back down (see Fig. 10). 

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