Page 293 - 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

802 Polymers, Thermally Stable

TABLE VIII Comparison of Interlaminar Shear Strength Interlaminar shear strength is used (Table VIII) to high-
versus Temperature and Time for Various Polyimide Ma- light levels of performance of key polyimide/carbon fiber
trix/Carbon Fiber Composites a
composites as a function of time and temperature. Com-
Interlaminar parison (Fig. 11) of the thermo-oxidative stability of dif-
shear ferent polyimide types highlights the superior stability of
strength Temperature
◦
Polyimide type (MPa) ( C) Time (hr) the wholly aromatic condensation systems. The presence
of polyene units in the polymers derived from acetylene-
Condensation 83 260 1000 terminated oligomers is reflected in a lower-than-expected
Addition—PMR 83 260 1000 stability.
Addition—bismaleimide 83 230 1000
Condensation 55 350 10
Condensation 55 320 1000 4. Quinoxaline Polymers
Thermoplastic 55 320 1000
Without reproducing the considerable achievements in
Addition—PMR 55 320 500
materials application of the polyimides, quinoxaline poly-
Addition—PMR 55 290 1000
mers have shown high levels of thermal and environmental
Thermoplastic 55 260 50000
stability together with the potential for commercial ap-
Addition—PMR 55 260 10000
plication in the fields of high-temperature adhesives and
Addition—bismaleimide 55 260 1000
laminating resins.
Thermoplastic 28 350 10
Polymers (LVIII) are prepared from the condensation
Addition—PMR 28 350 10
of aromatic tetraamines and aromatic tetra-carbonyl com-
Addition—PMR 28 320 1000
pounds (LIX) under melt or solution (polar solvent) con-
Condensation 28 290 10000
ditions and without the intervention of an isolable “open-
Thermoplastic 28 290 10000
chain” intermediate.
Addition—PMR 28 290 10000
Thermoplastic 28 230 50000
Addition—PMR 28 230 50000
Addition—bismaleimide 28 230 10000
a Reprinted with permission from Critchley, J. P., and Wright, W. W.
(1979). Polyimides as matrix resins for composites, Rev. High-Temp.
Mater. 4, 107. Copyright 1979 Freund Publishing House Ltd.

FIGURE 11 Comparison of thermo-oxidative stability of typical condensation and addition-type polyimides.
[Reprinted with permission from Wright W. W. (1981). Application of thermal methods to the study of the degrada-
tion of polyimides. In “Developments in Polymer Degradation” (N. Grassie, ed.), Chap. 1. Elsevier, Barking, England.
Copyright 1981 Elsevier Applied Science Publishers Ltd.]