Page 321 - Engineering Plastics Handbook

Polyamide-imide (PAI) 279

Environmental resistance
Polyamide-imides possess very good environmental resistance to water,
UV light, and radiation. Weather-Ometer tests, which exposed samples
to cyclic light and water conditions, were performed on polyamide-imide
bars for over 6000 h. Essentially no change in elongation or tensile
9
strength was apparent. After a 1-Grad (10 ) dose of gamma radiation,
polyamide-imide compounds show only a modest 5% drop in mechani-
cal properties [25].

Wear properties
As seen from the preceding friction and wear applications, polyamide-
imide compounds are a popular choice for these demanding applica-
tions. The graphs below (Fig. 12.20) show their performance against
notable high-performance polymer families such as polyetheretherke-
tone (PEEK) and polyimide. Having a high glass transition tempera-
ture approximately 130°C higher than PEEK, polyamide-imides enjoy
a decided advantage. With their mechanical properties almost twice
those of some polyimide compounds, polyamide-imide’s combination of
strength and thermal properties drives its accomplishment in this
area.

Pressure, MPa
0 2 4 6 8 10 12
1400
Velocity 50 ft/min (0.25 m/s)
Torlon 4301 35
1200 Torlon 4275
Torlon 4435 30
Vespel SP-21
1000 Victrex X50FC30 25
Wear depth, µin/h 800 20 Wear depth, µm/h

600
15
400
10
200 5

0 0
0.0 0.5 1.0 1.5 2.0
Pressure, kpsi
(a)
Figure 12.20 (a) Wear resistance at low velocity; (b) wear resistance at high velocity.