Page 269 - Academic Press Encyclopedia of Physical Science and Technology 3rd Polymer

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Encyclopedia of Physical Science and Technology En012c-604 July 26, 2001 16:2

778 Polymers, Thermally Stable

FIGURE 1 Comparison of stability of phenylene polymers with different linking groups in oxidizing atmosphere.
[Reprinted with permission from Wright, W. W. (1975). Comparison of stability of phenylene polymers with different
linking groups in oxidizing atmosphere. In “Degradation and Stabilization of Polymers” (G. Gueskens, ed.), pp. 43–45,
Elsevier, New York.]

advanced military aircraft, space craft, and missiles. Prin- II. CARBOCYCLIC AROMATIC SYSTEMS
cipal areas of materials development and real or potential
application in these advanced technology areas are listed Linear poly-p-phenylene is not a commercially avail-
here: able material; indeed it is rather typical of those in-
tractable systems generally referred to as “brick dusts.”
However, as perhaps the simplest example of a wholly
1. Films/varnishes/membranes: Wire and cable insula-
aromatic-linked polymer it is the standard against which
tion, heat-sealable or pressure-sensitive tapes, electrically
the thermal/thermo-oxidative stability of more complex
conductive film, electric motor slot liners, flexible printed
aromaticandheteroaromaticpolymershasbeenmeasured.
circuits, magnetic wire coatings, reverse osmosis mem-
Considerable improvements in tractability and processi-
branes.
bility have followed the introduction of the midchain flex-
2. Adhesives: Film and B-staged (on fiber substrate),
ible units shown below.
cryogenic and high-temperature application. Bonding
metal-to-metal (stainless steel, titanium, or beryllium al-
loy adherends), metal-to-composite, and composite-to-
composite use in honeycomb structures.
3. Fibers: Heat/flame resistant and high strength/high
modulus. Protective clothing, armor, and shields. Rein-
forcement for composites, fire hoses, V-belts. Hot gas fil-
tration systems, deceleration parachutes, solid rocket mo-
tors, nozzles, exist cones. Discussion will be restricted to those systems that have
4. Molding materials: Binders (brake pads, abrasive combined a high level of thermal stability with some prac-
wheels, etc.), self-lubricating bearings, friction-resistant tical utility.
flap track surfaces; abradable seals; rotors/vanes for
pumps; activators, piston rings, electrical connectors.
A. Polyphenylenes and Polyxylylenes
5. Composites: Matrix and reinforcement materials for
laminating and filament winding applications. Radomes, Poly-p-phenylene (I) has been synthesized by several

engine nascelles, fan and compressor blades, fan frames. conventional reactions—direct coupling of benzene/p,p -
6. Foams: Blown and syntactic. In-fill materials, air- derivatives, via a (soluble) poly-1,3-cyclohexadiene inter-
craft fire barriers, space shuttle insulation. mediate, or by Diels–Alder addition of diethynylbenzene