SYMPOSIA PAPER Published: 01 January 1953

The Measurement and Significance of the Mechanical Strength Properties of Plastics


Plastics materials because of their many unique properties are subjected to many strength tests. The majority of these are of limited value because they tell little about the fundamental or engineering nature of plastics. This is because the conventional tests are carried out at loading rates that do not simulate engineering application of the material. Further, at these rates, mechanical behavior is too complex for fundamental analysis.

The importance of long-time and short-time tests cannot be overemphasized. The long-time tests include creep, stress relaxation and long time strength. The data from these enable the designer to make a sound decision as to the best plastic material for a given application. They also indicate the molecular structure associated with each plastic. Short-time tests such as impact and highspeed tensile similarly provide useful engineering and fundamental information.

“Dynamic Testing” and “A Mechanical Equation of State for Plastics” are two recent developments of significance in strength testing. In the long run, dynamic test data applied to a mechanical equation of state may define the mechanical behavior of plastics over the entire spectrum of testing speeds.

Author Information

Adams, C., H.
Monsanto Chemical Co., Springfield, Mass.
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Developed by Committee: D20
Pages: 3–13
DOI: 10.1520/STP45661S
ISBN-EB: 978-0-8031-6250-1
ISBN-13: 978-0-8031-6253-2