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High heat resistance
is a distinguishing characteristic of CALIBRE* polycarbonate
resins. For an indication of temperature limits for molded
parts, two test methods are used - Deflection Temperature
Under Load (DTUL) and Vicat Softening Point values make
CALIBRE resins an ideal choice for many parts requiring
high thermal stability.
Deflection Temperature Under Load
DTUL is measured according to ASTM D 648.
The results relate to use temperatures under load and
also are a measure of rigidity at service temperatures.
DTUL measurements are affected by specimen molding conditions
and therefore should be used for screening purposes only
and not for direct measurement of specific structural
properties of a part, nor for identifying upper limits
of a useful temperature range. The typical DTUL of CALIBRE
polycarbonate resins - 258 to 270¡ÆF (126 to 132¡ÆC) - is
valid across the full range of melt flow rates. This data
was obtained with unannealed, injection-molded specimens
0.125 inch (3.2 mm) thick, under load of 264 psi (1.8
Mpa).
Vicat Softening Point
Vicat Softening Point is determined according
to ASTM D 1525. Vicat temperatures are generally higher
than DTUL temperatures. Measurements of Vicat are more
indicative of a polymer's actual softening point than
is DTUL, and are not usually affected by specimen molding
conditions. The high Vicat of CALIBRE resins is retained
throughout the melt flow rate range, decreasing only slightly
from 304¡ÆF (151¡ÆC) to 297¡ÆF (147¡ÆC) for melt flow rates
of 4 to 22. In addition, low Mold Shrinkage (0.005-0.007
in/in [0.005-0.007 mm/mm]) and Coefficient of Linear Thermal
Expansion (38 x 10-6 in/in/¡ÆF [68 x 10-6
mm/mm/¡ÆC]) make CALIBRE polycarbonate resins the material
of choice for applications requiring tight tolerances
at elevated temperatures. |