Page 273 - 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

782 Polymers, Thermally Stable

FIGURE 3 Comparison of the thermo-oxidative stability of p-hydroxybenzoic acid-based polymers. [Reprinted with
permission from Critchley, J. P., Knight, G. J., and Wright, W. W. (1983). “Heat Resistant Polymers—Technologically
Useful Materials,” Plenum, New York. Copyright 1983 Plenum Press.]

poly(p-phenylene sulfide) (PPS) remains the only ma- and camshafts. In tailoring the properties of PPS to suit
jor commercial development for this class of thermoplas- the specific application, both amorphous and crystalline
tic aromatic polymer. Although alternative PPS products versions of the resin have been investigated, and in this
are beginning to be marketed by others (General Electric, regard the potential of PPS fibers has been investigated.
Bayer AG, Mobay, and Hoechst-Celanese), the Phillips’ The application of zone-drawing and zone-annealing tech-
Ryton material still controls around 95% of the market. niques has recently been used to improve the mechanical
A widening range of high-temperature applications has properties of PPS fibers.
emerged for both reinforced and unreinforced PPS, in- PPS is characterized as a thermosetting thermoplastic.
cluding, ball valves, chip- and fiber-carriers, encapsulants, “Curing” occurs on heating in oxygen or in the pres-

TABLE II Comparison of Properties of a Polyester (Ekonol) with Other High-Temperature
Resistant Polymers a
Polyester Polysulfone Polyimide Polytetra-
Property (Ekonol) (Astrel 360) (Vespel) fluoroethylene
Density (g/ml) 1.44 1.36 1.40 2.13
Flexural strength (MPa) 74 119 81–97 —
Flexural modulus (GPa) 7.1 2.7 3.2 0.6
Compresive strength (MPa) 226 124 166 7
Dielectric strength (V/mil) 660 300 430 620
Dielectric constant 3.8 3.9 3.6 2.1
4
Dissipation factor (×10 ) 2 30 34 3
16
Volume resistivity ( -cm) 10 15 10 13 10 –10 17 10 18
Water absorption, 24 hr at RT (%) 0.02 0.22 0.30 0.01
Coefficient of static friction 0.10–0.16 — 0.25–1.2 0.05–0.08
Thermal conductivity 18.0 6.0 6.0
2 ◦
10 −4 cal/(sec)(cm) ( C/cm)
a Reprinted with permission from Mark, H. F., Gaylord, N. G., and Bikales, N. M., eds. (1971). “Ency-
clopedia of Polymer Science and Technology,” Vol. 15, p. 292, Wiley (Interscience), New York. Copyright
1971 John Wiley & Sons, Inc.