Page 203 - Engineering Plastics Handbook

176 Engineering Plastics

2.0
BPADA-MPD PEI @ 0.8 mm
1.5 BPADA-MPD PEI @ 1.6 mm
Absorbance 1.0

0.5

0.0
420 520 620 720 820 920 1020
Wavelength
Figure 8.7 UV-visible spectra of a typical BPADA-MPD PEI at 0.8-
and 1.6-mm (0.032- and 0.063-in) thickness.

Processing Options
Polyetherimides have been used as a metal, glass, ceramic, and thermoset
replacement. Commercial grades have been used primarily in injection-
molding applications where these fast-cycling resins have high efficiency
for large production runs. In replacement of metals, PEI resins allow for
design of complex shapes, often incorporating features that would other-
wise require combinations of several metal parts into a single plastic part.
This consolidation of parts often makes manufacturing simpler so that even
if the cost of the resin is higher than the cost of the metal, the total cost of
making and assembling the object is reduced. In addition, parts consoli-
dation reduces the potential for errors during assembly and may simplify
manufacturing supply concerns.
The pelletized form of the polymer supplied to converters is fully poly-
merized. No chemical-curing reaction is needed, and the polymer can be
stored under ambient conditions almost indefinitely. There are no shelf-
life issues as seen with some amide-acid polymers.
PEI resins have been extruded into film and sheet. Since they are ther-
moplastic, both sheet and film can be formed and drawn in secondary
operations. PEI film can be used in many electrical applications, such as
the manufacture of capacitors and flexible circuits. These films can also
be laminated or coextruded to make various multilayer structures. PEI
films are often laminated with metals, such as copper, which are then
made into electric circuits.
PEI resins may also be extruded into rods and blocks, which can be sub-
sequently machined into parts. This is useful where smaller production