ASTM D1621-16 Compressive Properties of Rigid Cellular Plastics

ASTM D1621-16 specifies the test conditions for determining the compressive properties of rigid cellular materials, particularly expanded plastics. Rigid foams are typically used in the construction industry as sound and thermal insulation. Calculations referenced in this standard include yield points, compressive strength, and compressive modulus. Suitable systems for this application include 3300 Series and 5900 Series electromechanical testing machines equipped with compression platens. 

The challenges of testing to this standard are:

• Displacement measurement
• Non-parallel specimens
• Test setup

Instron® Solution:

• Displacement measurement – When  measuring compressive displacement, ASTM D1621-16 allows for measurement using direct compression platen displacement or via crosshead extension by eliminating the effects of system compliance. Instron offers linear variable displacement transducers (LVDTs) for measurement directly from the platens. The 2601-04x series LVDTs can mount directly on the 2501 series compression platens. To measure via crosshead extension, Bluehill® Universal testing software can do an automatic compliance correction to eliminate system compliance from the test curve.
• Non-parallel specimens – The parallelism of the compression platens is important, and it is recommended that a spherical seating style compression platen is utilized along with a rigid platen. The self-aligning nature of this fixture will maximize the contact area between the platen and the specimen. Swivel seating can be placed on the platen attached to the instrument's base or load cell in the moving crosshead. To reduce the possible effects from off-center loading, it is preferred to place the swivel seat in the base.
• Test setup – To make testing easier, leaving a 10 to 30 mm gap between the specimens allows the user to quickly and easily remove the tested specimens and position new ones. The preload function in Bluehill Universal software automatically moves the upper compression platen down to precisely touch the specimen at a pre-defined load. The preload function reduces the amount of operator interaction, saving time and improving accuracy.

It is important to review ASTM D1621-16 in order to fully understand the test setup, procedure, and results requirements.