Composites reinforced elastomers

Uniaxial deformations give prolate (needle-shaped) ellipsoids, and biaxial deformations give oblate (disc-shaped) ellipsoids [220,221], Prolate particles can be thought of as a conceptual bridge between the roughly spherical particles used to reinforce elastomers and the long fibers frequently used for this purpose in thermoplastics and thermosets. Similarly, oblate particles can be considered as analogues of the much-studied clay platelets used to reinforce a variety of materials [70-73], but with dimensions that are controllable. In the case of non-spherical particles, their orientations are also of considerable importance. One interest here is the anisotropic reinforcements such particles provide, and there have been simulations to better understand the mechanical properties of such composites [86,222],... 

The SIN s from castor oil and the other oils were tough materials, either reinforced elastomers or impact resistant plastics depending on their composition and whether phase inversion had occurred. Impact strengths in the range of 40-60 J/m were obtained. The glass transitions of the rubber phase of the SIN s tended to be a little higher than those shown in Table IV. The polystyrene phase... 

Jao, S.H. and McGarry, F.J. (1992a) On the failure work and modulus of composites reinforced by thin elastomer-coated fibers. J. Composite Mater. 26, 2632-2654. 

For the preparation of filler reinforced elastomer composites, most frequently commercial rubber grades with variable microstructure and broad molar mass distribution are applied. The typical rubber grades, considered in the present review, are as follows ... 

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). 

S. Saikrasun and T. Amomsakchai. Phase behavior and properties of in situ-reinforcing elastomer composites based on thermoplastic elastomers and thermotropic liquid crystalline copolyester. J. Appl. Polym. ScL, 101 1610-1619, 2006. 

With both the PEA/P(S-co-MMA) and PB/PS IPN s, an important variable is the ratio of elastomer to plastic in the final material. When the plastic component predominates, a type of impact-resistant plastic results. In this manner the PB/PS IPN s are analogous to the impact-resistant graft copolymers. When the elastomer component predominates, a self-reinforced elastomer results, the behavior resembling that of the ABA-type block copolymers (thermoplastic elastomers) described in Section 4.4. When the overall compositions of both the PB/PS and the PEA/P(S-co-MMA) series are close to 50/50, the materials behave like leathers. 

Reinforced elastomers are one of the oldest and most important classes of composite materials (Ruffell, 1952 Sellers and Toonder, 1965 Stern, 1968, p. 278). When the automobile first became popular, the need to toughen tire rubber, especially against abrasion, became obvious. Although zinc oxide had already attained widespread use as a rubber colorant, in 1905 Ditmar realized the true importance of this material as a reinforcing agent for rubber. Many industry veterans can still remember when tires had white treads. However, such tire treads usually lasted less than 5000 miles, and the need for further improvements was imperative. 

When the polymeric component forms the continuous phase, spheres, cylinders, or platelets may be added, as illustrated under reinforced polymers. The fiber composites are the most highly researched, as far as different modes of mixing are considered. The filaments may be continuous or discontinuous, or oriented or random in the matrix, with many subclasses of partial orientation possible (not shown). The tape composites are interesting since in some quarters these may be considered a two-dimensional analog of the highly oriented, continuous fibers embedded in a plastic matrix. The reinforced elastomers differ from the reinforced plastics in two ways the mechanical properties of the polymeric substrate, and the size of the reinforcing particles with respect to polymer chain dimensions. Because of the poor properties often obtained, it is rare to see a research paper on large particles dispersed in an elastomer. 

The syntheses illustrated above make tough plastics, reinforced elastomers, or leathery materials suitable for broad-temperature-damping compositions, depending on the ratio of plastic to rubber, and extent of molecular mixing. Properties will be discussed in Chapter 6 and 7. 

In Example 21 of Reference 8, Hutchinson et al describe the heat distortion characteristics of the materials (see Table 8.5. Samples A and B were based on 4 4 -diphenyl methane diisocyanate, the latter prepared at a higher temperature. Sample C was prepared from a polyurethane composition having a Tg of -25 C. While the impact strength of C is much higher, it is a softer material with a lower heat distortion temperature. Since the material contains 60% polyurethane, the material is better described as a reinforced elastomer. Clearly experiment B yields the highest heat distortion temperature. 

Chakraborty S, Sahoo N G, Jana G K and Das C K (2004) Self-reinforcing elastomer composites based on ethylene-propylene-diene monomer rubber and liquid-crystalline polymer, J Appl Polym Sa 93 711-718. 

Saikrasun S and Saengsuwan S (2009) Thermal decomposition kinetics of in situ reinforcing composite based on polypropylene and liquid crystalline polymer, J Mater Proc Technol 209 3490-3500. Saikrasun S, Limpisawasdi P and Amornsakchai T (2009) Effect of LCP and rPET as reinforcing materials on rheology, morphology, and thermal properties of in situ microfibrillar-reinforced elastomer composites, J Appl Polym Sci 112 1897-1908. 

In reinforced plastics various inorganic materials are dispersed in the polymer. Carbon black reinforced elastomers have already been considered see Section 9.16.2. For fiber composites, two subtypes are important, the short fiber-containing materials, which are thermoplastic, and the continuous filament types, which cannot flow. While short fibers can be melt blended with thermoplastics, they are often embedded in monomeric mixes, followed by polymerization in situ. Continuous fibers are always processed via monomeric mixes which can flow over the beds of fibers. Of course, these monomeric mixes may have polymers or prepolymers dissolved in them, raising the viscosity, and reducing shrinkage on polymerization. An example of the continuous filament type is a tape composite, familiar as the strapping tape used for packaging. 

Elastomer Composites Reinforced with Randomly Dispersed Long Nonwoven Fibers... 

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