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How to Test Plastic Properties

Deformation Under Load

Deformation Under Load indicates the ability of rigid plastics to withstand continuous short-term compression without yielding and loosening when fastened as in insulators or other assemblies by bolts, rivets, etc. It does not indicate the creep resistance of a particular plastic for long periods of time. It is also a measure of rigidity at service temperatures and can be used as identification for procurement.

The specimen is placed between the anvils of the testing machine, and loaded at 1000 psi. (Sometimes other loadings may be specified). The gauge is read 10 seconds after loading, and again 24 hours later. The deflection is recorded in mils. The original height is calculated after the specimen is removed from the testing machine by adding the change in height to the height after testing. By dividing the change in height by the original height and multiplying by 100, the percent deformation is calculated. This test may be run at 73.4, 122, or 158 °F. ASTM D-621.