Heat-resistant composites

Hexanitroshlbene (HNS) has been reported for use in achieving stage separation in space rockets and also as a component of heat-resistant compositions employed in the Apollo spaceship and for seismic experiments on the moon [107]. Similar to HNS, 3,3 -diamino-2,2, 4,4, 6,6 -hexanitrodiphenyl (DIPAM) has also been reported for such applications [108]. 

Hiroaki, K., Yoshio, B., Chunyi, Z., Tang, C., and Goldberg, D. 2008. Heat resistant composite composition and method for making the same. Jpn. Kokai Tokkyo Koho, JP 2008007699. 

David, C., Demay, J., Gardelein, M., and Lejeune, M. 2003. Heat resistant composition for electric cables contains organic polymer, a fusable ceramic tiller which melts below the limiting temperature and a refractory filler with a high melting point. EP 1347464. 

Solvent resistant laminates for printed circuits were manufactured by coating of copper foil with a solution of PPO, BPA/DC, bis(4-maleimidophenyl) ether and Zn octoate in toluene the coated foil was laminated with PPO-impregnated glass fabric [47]. Similar result was achieved by the modification of PPO with polyfunctional cyanates or maleimides, liquid polybutadiene and a polymerization catalyst [48], A solvent and heat resistant composition for printed circuits consists of copoly [(2,6-dimethylphenylene)-(2,3,6-trimethylphenylene)]oxide, maleic anhydride grafted poly-1,2-butadiene, bis(4-maleimidophenyl)methane, BPA/DC and toluene. BPA/DC prepolymer may be used instead of the monomer [49]. 

Keywords polyorganosiloxanes, polyphenylsilsesquioxane-polydiorganosiloxane block copolymers, heat-resistant composites. 

Summary Comparative analysis is carried out of some physical-chemical and physical-mechanical properties of polyorganosiloxane block copolymers of linear and linear-ladder structure. Advantages of polyorganosiloxane block copolymers are demonstrated in terms of thermal stability and physical-mechanical performance. There is an opportunity for the development of new heat-resistant composites for various branches of industry. 

The data presented show that a proper selection of modifiers and curing parameters makes it possible to develop heat resistant composites with high temperature resistance. The composites are superior to similar materials based on BPA/ECH epoxy and epoxynovolak resins. 

Khotimchenko, Vasiloi, Demskaya, and co-workers (The Scientific Industrial Association Quartz, Leningrad) [107,108] used sol-gel technology for making quartz glass. A heat-resistant composite was obtained from tetraethoxysilane by using quartz fibers (diameter... 

Carbon composite materials are used widely in a number of applications, including high-performance graphite sports equipment such as tennis racquets, golf clubs, and bicycle wheels (T FIGURE 22.31). Heat-resistant composites are required for many aerospace applications, where carbon composites now find wide use. 

Weng BJ, Hwung JJ, Chen Cl, Hsu SE, Heat resistant composites of graphite fibre reinforced phosphate ceramics, Doyama M, Somiya S, Chang RPH, Kimura S, Kobayashi A, Umekawa S eds.. Composites Corrosion/Coating of Advanced Materials, Proc MRS Int Meeting on Advanced Materials 4, Materials Research Society, Tokyo, 135 140, 2-3 Jun 1998. 

The entire first SGI, including the SGs and pumps, was located in the center of the ship in an isolated RC. The three PWRs were aligned vertically in a plane perpendicular to the keel and were surrounded by a large water-filled steel shield tank. The biological shield located above the three PWRs was made of limonite concrete and a heat resistant composition of graphite and boron. 

It is shown, that the most heat-resistant composites are obtained at use of hardeners D-2, D-1, and as an established fact, equivalent parity of epoxy oligomers the hardener ( 8-10% surplus of a hardener) creates favorable conditions for increase of thermal stability of composites. 

Heat resistant composites on the basis of carbon and hafnium... 

In addition to carbon and glass fibers ia composites, aramid and polyimide fibers are also used ia conjunction with epoxy resias. Safety requirements by the U.S. Federal Aeronautics Administration (FAA) have led to the development of flame- and heat-resistant seals and stmctural components ia civiUan aircraft cabias. Wool blend fabrics containing aramids, poly(phenylene sulfide), EDF, and other inherently flame-resistant fibers and fabrics containing only these highly heat- and flame-resistant fibers are the types most frequently used ia these appHcations. 

Appllca.tlons. The principal appHcations of nickel-base superalloys are in gas turbines, where they are utilized as blades, disks, and sheet metal parts. Abcraft gas turbines utilized in both commercial and military service depend upon superalloys for parts exposed to peak metal temperatures in excess of 1000°C. Typical gas turbine engines produced in the United States in 1990 utilized nickel and cobalt-base superalloys for 46% of total engine weight (41). However, programs for future aerospace propulsion systems emphasize the need for lightweight materials having greater heat resistance. For such apphcations, intermetallics matrix composites and ceramic composites are expected to be needed. 

Titanium siUcides are used in the preparation of abrasion- and heat-resistant refractories. Compositions based on mixtures of Ti Si, TiC, and diamond have been claimed to make wear-resistant cutting-tool tips (157). Titanium siUcide can be used as an electric—resistant material, in electrically conducting ceramics (158), and in pressure-sensitive elastic resistors, the electric resistance of which varies with pressure (159). 

Poly(ethyl methacrylate) (PEMA) yields truly compatible blends with poly(vinyl acetate) up to 20% PEMA concentration (133). Synergistic improvement in material properties was observed. Poly(ethylene oxide) forms compatible homogeneous blends with poly(vinyl acetate) (134). The T of the blends and the crystaUizabiUty of the PEO depend on the composition. The miscibility window of poly(vinyl acetate) and its copolymers with alkyl acrylates can be broadened through the incorporation of acryUc acid as a third component (135). A description of compatible and incompatible blends of poly(vinyl acetate) and other copolymers has been compiled (136). Blends of poly(vinyl acetate) copolymers with urethanes can provide improved heat resistance to the product providing reduced creep rates in adhesives used for vinyl laminating (137). 

Table 19. Composition of Heat-Resisting Chromium Steels...

To optimize the lesin system foi a given process and part, consideration should be given to fillers that can gready affect the cost and performance of the composite. Because of their low viscosity, fillers can often be added to polyesters. Fillers are often much cheaper than the resin they displace, and they can improve the heat resistance, stiffness, and hardness of the composite. Certain fillers, such as fumed siUca, impart thixotropy to the resin, increasing its resistance to drainage. 

Most processors of fiber-reinforced composites choose a phenol formaldehyde (phenoHc) resin because these resins are inherently fire retardant, are highly heat resistant, and are very low in cost. When exposed to flames they give off very Htde smoke and that smoke is of low immediate toxicity. PhenoHc resins (qv) are often not chosen, however, because the resole types have limited shelf stabiHty, both resole and novolac types release volatiles during their condensation cure, formaldehyde [50-00-0] emissions are possible during both handling and cure, and the polymers formed are brittle compared with other thermosetting resins. 

The Michael addition reaction has attracted many researchers as a route to convert high melting BMI building blocks into resins with improved processibihty as compared with the BMI precursors. Heat-resistant resin compositions are prepared from BMI and para- or y /i7-aminophenol (38). The idealized stmcture of such a BMI—y -aminophenol adduct follows. 

Heat-resistant resin compositions based on bismaleknide—epoxy blends are achieved by reaction of a BMI—y -aminophenol [591-27-5] (1 1) adduct with epoxy. This prepolymer is fully cured with an imida2ole catalyst (54). Blends of hydroxy-terminated BMI—aminophenol adducts can easily be B-staged, that is, prepolymerked, and subsequendy ground to provide a powder that can be molded by the appHcation of heat and pressure. 

Gold [7440-57-5] Au, is the principal constituent of gold-colored alloys. It contributes gold color kicreases the specific gravity raises the melting pokit, if that of the alloy is below that of gold and kicreases ductihty, maHeabiUty, corrosion, and stain resistance. Gold produces heat-treatable compositions with copper, platinum, and zkic. It is useful ki amounts of 25—100 wt %. 

Copper [7440-50-8] Cu, produces a reddish color and reduces the melting pokit of the alloy. It produces heat-treatable compositions with gold, platinum, and palladium that result ki kicreased hardness, strength, and generally improved physical properties. The tarnish resistance of the alloy is usually decreased. The gold—copper, Au—Cu, system is the fundamental system of many dental gold alloys. Copper has a useful range of 0—20 wt %. 

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