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ISO 75 Test Standard Explained

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Heat Deflection Temperature (HDT) - ISO 75

The temperature at which a test specimen deflects a specified amount when loaded in 3-point bending at a specified maximum outer fiber stress. Deflection temperature is used to determine short-term heat resistance.

HDT Testing Methods
Method	Outer Fiber Stress (MPa)
A	1.80
B	0.45
C	8.00

Testing is either performed using edgewise or flatwise specimen orientation. Testing parameters vary between the two configurations as shown below.

Specimen Orientation Parameters
Orientation	Dimensions (mm)	Span (mm)	Standard Deflection	Diagram
Edgewise	120x9.8-15x3-4.2	100	0.32
Flatwise	80x10x4	64	0.34

ISO 10350 Note

ISO 10350 requires testing in the flatwise orientation.

Similar Standards

ASTM D648

Property information for specific grades of resin are available in the Prospector Plastics Database.