Thermal insulators aircraft applications

The fiber offers fire resistance and high thermal insulation together with low smoke emission, low electrical conductivity and a weight saving. Current applications include aircraft fuselage thermal insulation, aircraft fire blockers, fire protective clothing, personal insulation and fire retardant insulation boards for special lightweight applications. Table 23.7 lists the vertical burn test results for several Curlon fiber blends. 

The applications for addition polyimides are for electronic/electrical materials such as printed circuit boards and insulators, as matrix resins for structural composites in aircraft and as thermal insulation materials. Recently the market for polyimide based structural composites has suffered from the termination and reduction of military aircraft programs. However, the possible emergence of the High Speed Civil Transport program (HSCT) may offer an opportunity for addition polyimides (2). 

Pyrolytic graphite was first produced in the late 1800s for lamp filaments. Today, it is produced in massive shapes, used for missile components, rocket nozzles, and aircraft brakes for advanced high performance aircraft. Pyrolytic graphite coated on surfaces or infiltrated into porous materials is also used in other applications, such as nuclear fuel particles, prosthetic devices, and high temperature thermal insulators. 

Flame Resistance. Traditionally, small-scale laboratory flammability tests have been used to initially characterize foams (38). However, these do not reflect the performance of such materials in bulk form. Fire characteristics of thermal insulations for building applications are generally reported in the form of qualitative or semiquantitative results from ASTM E84 or similar tunnel tests (39). Similar laiger scale tests are used for aircraft and marine applications. 

PBI is often used in fiber form for a variety of applications such as protective clothing and aircraft furnishings. Parts made from PBI are used as thermal insulators, electrical connectors, and seals. 

Wire, cable, film, and fiber. Aurum can be extruded into wire, cable, film, and fiber (Fig. 10.6). The extruded wire and cable are for electrical insulation with outstanding thermal, mechanical, chemical, and electrical properties. Aurum film is available in 1- to 22-mil-thick rolls from Westlake Plastics. The applications include wire, cable, and optic fiber insulation industrial belts heat and radiation panels and other electric and thermal insulation devices. Aurum monofilament and multifilament can be woven and braided into a variety of high-performance industrial and aircraft products including paper-making belts and jet-engine insulation. 

Greebler, P. Thermal Properties and Applications of High Temperature Aircraft Insulation, American Rocket Society, 1954. Reprinted in Jet Propulsion, November-December 1954. 

Esters of trimellitic (1,2,4-benzenetricarboxylic acid) anhydride provide excellent resistance to volatile loss and oxidation under heat ageing conditions making them the material of choice in applications for which high-temperature thermal stability is required. Insulation for automotive and aircraft cables are typical areas of application. The low volatility of trimellitates is also exploited in car interior components. 

Typical uses of polyimide include electronic applications, sleeve bearings, valve seatings, and compressor vanes in jet engines. Other uses include aircraft and aerospace applications with high performance requirements. They are used for printed circuit boards in computers and electronic watches for both military and commercial uses. Polyimides are used in the insulation of automotive parts that require thermal and electrical insulation, such as wires used in electric motors, wheels, pistons, and bearings. 

Polymer adhesives have found their place in numerous electronics applications. Major uses include eommercial/consumer products computers and military, space, automotive, medical, and wireless communications. Some adhesives may be used aeross several applications while others have been formulated to meet applieation-specific requirements. For example, reworkability is not a consideration for high-production, low-cost consumer products such as cell phones or calculators, but is important for high-value, high-density printed-wiring boards (PWBs) used in military and spaee electronics. Further, thermal stability at high temperatures is required for near-engine electronics in automobiles, aircraft, and for deep-well sensors, but not for office computers. The major applications for polymer adhesives are to attach and electrically insulate or to electrically connect components, devices, connectors, cables, and heat sinks to printed-circuit boards or to thin- or thick-film hybrid microcircuits. In addition, over the last several decades, new uses for adhesives have emerged for optoelectronic (OE) assemblies, microelectromechanical systems (MEMS), and flat-panel displays. 

These studies show that, among many technical areas that require attention before a hydrogen-fueled aircraft can be a reality, one of the most important is thermal protection for the fuel tanks. Both the subsonic studies and studies of a hypersonic vehicle application indicate that low-density foams are attractive insulations for the LH2 fuel tanks, if reliability and adequate life can be established. Although this type of insulation has been used extensively for large throw-away booster stages for space application, the lack of reuse requirements has not demanded extensive investigation of the cyclic life of foam insulations. 

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