Reinforced thermoset general properties

Examples of major plastic families Thermoplastic thermal properties are compared to aluminum and steel General properties of thermoplastic General properties of thermoset plastic General properties of reinforced thermoplastic General properties of reinforced thermoset plastic Examples of drying different plastics (courtesy of Spirex Corp.)... 

Table 1.6 General properties of reinforced thermoset plastic... 

Although thermoplastics, thermosets and elastomers can be used as matrix of polymer composites, thermosets are more widely used mainly due to the processing techniques employed in their manufactme, that allow for the easy use of long fibers, mats and fabrics as reinforcement. Thermosets are also generally more thermally stable than thermoplastics, and these two reasons lead to products with significantly higher mechanical properties which are less affected by thermal variations than thermoplastic composites [1,2,12],... 

Description and general properties. Polymer matrix composites (PMCs) consist of a pol)oner matrix or resin reinforced with glass fibers and to a lesser extent carbon, boron and pol)r-aramide fibers. The resin systems used to manufacture advanced composites are of two basic types thermosets and thermoplastics (see Chapter 11). Thermosetting resins predominate today, while thermoplastics have only a minor role in advanced-composite manufacture. Thermoset resins require the addition of a curing agent or hardener and impregnation onto... 

Composites consist of two (or more) distinct constituents or phases, which when combined result in a material with entirely different properties from those of the individual components. Typically, a manmade composite would consist of a reinforcement phase of stiff, strong material, embedded in a continuous matrix phase. This reinforcing phase is generally termed as filler. The matrix holds the fillers together, transfers applied loads to those fillers and protects them from mechanical damage and other environmental factors. The matrix in most common traditional composites comprises either of a thermoplastic or thermoset polymer [1]. 

The fibres generally used for polymer reinforcement are glass, carbon and less often PTFE or metals. For use in thermosets, glass or carbon fibre may be used in the form of a pressed mat, or bundles of fibres may be laid in a preferred orientation. This enables anisotropic properties to be obtained where this is beneficial. The alternative is to disperse chopped fibres randomly in the polymer matrix. This gives... 

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). 

In some applications, it is useful to incorporate nonplastic substances into a plastic object, to reduce its cost or improve its performance in some way. Fillers are typically used to lower the cost of the plastic, and generally consist of minerals of some kind. Reinforcements are often more expensive, per unit mass or volume, than the plastics, but provide improvement in properties such as strength and/or rigidity. They usually consist of either organic or inorganic fibers. Use of fillers and reinforcements is less common in packaging applications than in uses such as automotive components or housewares, but is sometimes significant. In addition, these additives are more commonly used with thermoset polymers than with thermoplastics. 

These assumptions are not always justifiable when applied to plastics unless modification has occurred. The classical equations cannot be used indiscriminately. Each case must be considered on its own merits, with account being taken of such factors as the mode of deformation, the service temperature and environment, the fabrication method, and so on. In particular, it should be noted that the past traditional equations that have been developed for other materials, principally steel, use the relationship that stress equals the modulus times strain, where the modulus is constant. Except for thermoset reinforced plastics and certain engineering plastics, many plastics do not generally have a constant modulus. Different approaches have been used for the nonconstant situation some are quite accurate. The drawback is that most of these methods are quite complex, involving numerical techniques that are not attractive to designers. One method that has been widely accepted is this so-called pseudoelastic design method. In this method appropriate values of such time-dependent properties as the modulus are selected and substituted into the standard equations. 

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