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CALIBRE* polycarbonate resins meet
a wide range of impact requirements- from 1.5 to 18.0
ft-lb/in (80 to 950 J/m) notched Izod impact strength.
However, understanding the "balance" of end-use
temperature and impact requirements is crucial in selecting
a resin for a specific application.
Instrumented Dart Impact
The instrumented, high-speed, dart impact
test yields a plot of the force (load) and elongation
(displacement) required to puncture a disc with a dart.
The dart delivers a multiaxial impact, which is measured
to determine the total energy needed to fracture the
disc.
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9- Instrumented Dart Impact Strength versus Melt Flow Rate, CALIBRE 300 and 300EP Series Resins
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Figure 9 is a plot of the total energy required to fracture
injection molded, 0.125 inch (3.2mm) thick discs versus
the melt flow rates of CALIBRE 300 and 300 EP Series
resins at -20, 73 and 100¡ÆF (-29, 23 and 38¡ÆC). The
test was conducted according to ASTM D 3763, using a
1.5 inch (38.1 mm) diameter aperture. As was evident
in previous tests, the impact strength of the resins
decreases slightly with increasing melt flow rate. The
lower melt flow rate resins are seen to be slightly
tougher than their higher melt flow rate counterparts.
However, all samples exhibited ductile behavior.
For a CALIBRE resins of a given melt flow rate, the
total energy value required to produce a fracture remains
essentially the same across the temperature range of
-20 to 100¡ÆF (-29 to 38¡ÆC).
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10- Instrumented Dart Impact versus Thickness, CALIBRE 300 and 300EP 22 MFR Resin
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When instrumented dart impact strength is plotted against
sample thickness, the total energy of the impact decreases
linearly with sample thickness. However, all of the
samples failed in a ductile manner. (There was no thickness
at which the failure mechanism changed from ductile
to brittle as there is when using notched Izod impact.)
Figure 10 illustrates the relationship between the total
energy of the instrumented dart impact versus thickness
for CALIBRE 300 EP 22 MFR resin. Data are shown for
both unaged specimens and those aged 64 hours at 248¡ÆF
(120¡ÆC). All impacts were ductile.
The differences in energy and the changes in the mode
of failure between the notched Izod and the instrumented
dart impact tests stress the importance of completely
understanding the test method and results. No one physical
property test method, performed on a test specimen,
can completely predict a fabricated part's performance.
Test data should be used for initial material screening
and to understand material behavior under the test conditions.
Impact Strength
Tensile Strength
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