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Wrap-reel (Hand-Operated)
The heat deflection
temperature of plastic materials is the temperature at which the
material deflects by a specified amount under the action of a specified
stress. It is determined by supporting a rectangular test specimen over
two cylindrical edged blocks and pressing it at the center of the
supported span through a cylindrical edged loading tip. The test
specimen, along with the supports and the loading frame, is kept in a
high temperature bath whose temperature is slowly raised. The
temperature at which the test specimen deflects through a predetermined
distance is the heat deflection temperature of the material under test
The GLOBE Heat Deflection
Temperature Tester consists of two cylindrical rollers for supporting
the test specimen on, another cylindrical roller for applying force on
the test specimen; a liquid bath in which the test specimen and loading
frame are kept for raising the temperature of the test specimen, a set
of weights to give the desired stress on the test specimen, and a
deflection measuring arrangement for measuring the deflection of the
test specimen under the specified stress.
The support block has two
cylindrical supporting edges parallel to and mounted at a specified
distance from each other in an aluminium frame. The loading tip applies
the desired stress at the center of the supported span of the test
specimen. This tip is held at the lower end of a vertical rod, which is
guided inside a metallic sleeve and is constrained to move without
rotating along a vertical axis. The upper end of the vertical rod
carries a plate on which dead weights can be placed to apply force on
the test specimen.
The deflection measuring
arrangement consists of a dial indicator to indicate the deflection of
the rod carrying the loading tip. A set of dead weights is provided to
apply forte on the test specimen for applying the specified stress.
The immersion bath
consists of a double walled reservoir having its inner walls made from
mild steel sheet and outer walls of CRCA cold rolled sheet. The space
between the two walls is filled with mineral wool for providing thermal
insulation. The liquid in the bath is heated by means of an immersion
heater. An electronic voltage regulator controls the rate of rise of
its temperature. The temperature is measured in the vicinity of the
loading tip with the help of a digital temperature indicator. A back-up
thermostat is provided to restrict the maximum temperature of the bath.
An electric stirrer gives a uniform temperature in the bath. A cooling
coil through which cold water can be circulated enables fast cooling of
bath liquid for continuous testing.
The bath is finished in
white stove enamel painting. All other components are either bright
chrome plated or made out of non-corrodible materials to give them a
corrosion resistant finish.
Technical Specifications
Dimensions of the test specimen
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3 to 4.2 mm wide
9.8 to 15 mm thick
120 +- 10 mm long
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Distance between supporting edges
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100 +- 2 mm
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Radius of supporting and loading edges
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3.0 +- 0.2 mm
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Temperature
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Upto 300oC (least count 1oC)
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Deflection measurement
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0 - 10 mm (least count 0.01 mm)
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Force on the specimen
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200 to 1800 g in steps of 25 g
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Related Specifications
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IS 867 - 1963
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Methods of Test for Phenolic Moulding Materials
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IS 13360 (Part 6 / Section 3) - 1997
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Plastics - Methods of Testing
Part 6: Thermal Properties
Section 3: Determination of Temperature
of Deflection under Load
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IS 13411 - 1992
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Glass Reinforced Polyester Dough
Moulding Compounds - Specification
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ISO 75 - 1 - 1993
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Plastics - Determination of Temperature of
Deflection under Load
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ASTM D 648 - 1982
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Standard Test Method for Deflection
Temperature of Plastics under Flexural Load
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