Page 278 - Academic Press Encyclopedia of Physical Science and Technology 3rd Polymer

P1: GPQ Final Pages/GNB P2: GTV
Encyclopedia of Physical Science and Technology En012c-604 July 26, 2001 16:2

Polymers, Thermally Stable 787

TABLE V Comparison of Tensile Strength at Elevated Temperatures of Various
Glass-Reinforced Thermoplastics a
Glass
◦
Tensile strength (MPa) at ( C)
content
Polymer type (wt%) 23 95 150 175 205 230
Polysulfone (P1700) 40 119 103 16 8 — —
Polyethersulfone (200P) 40 157 134 90 34 21 —
Polyarylsulfone (Astrel 360) 0 90 72 60 51 39 22
Poly(phenylene sulfide) 40 160 77 56 33 8 —
Poly-p-oxybenzoate 0 96 77 64 54 44 —
Polyimide 30 90 43 33 21 16 12
Polyamideimide 0 189 137 112 79 57 48
TFE/HFP copolymer 20 35 29 16 8 — —
TFE/E copolymer 20 78 47 43 14 — —
a
Courtesy of J. Theberge, LNP Corporation.

“Victrex” range. PEEK (Litrex K) has also been devel- by weaving, braiding, or knitting to give a drapable fabric.
oped as a commercial material by Petrochemie Danubia Heat and pressure has resulted in a consolidated compos-
GmbH. ite with good carbon fiber dispersion. The other approach
APC-2 is a thermoplastic prepreg consisting of a 60% has involved the dispersion of fine PEEK powder (average
by volume unidirectional web of high-strength fiber im- particle size 7 µm) onto the carbon fiber reinforcement.
pregnated with PEEK resin. Although it has demonstrated The improved wettability of the fine particles has proved
processing advantages over more conventional thermoset to be a significant advantage in the material handling char-
prepregs—shorter processing time, indefinite shelf-life— acteristics. By comparison with conventional thermosets,
the APC-2 prepreg is stiff and inflexible (boardy). Two ap- thermoplastic composites such as PEEK and PPS exhibit
proaches have been made to improve the so-called drapa- improved mechanical properties at temperature, chemical/
bility of the prepreg. In the first a filament-to-filament “co- solvent resistance, and, critically, tolerance to acciden-
mingled” blend of carbon and PEEK fibers is processed tal damage and environmental (particularly hot/wet)

FIGURE 8 Thermal and thermo-oxidative stability of PEEK. [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.]