ISO 844 Rigid Cellular Foam Plastic Compression Testing

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ISO 844 Rigid Cellular Foam Plastic Compression Testing

ISO 844 provides specific testing procedures for determining the compressive strength of rigid cellular plastics.

What Is ISO 844?

ISO 844 specifies a test method for determining the compressive properties of strength and modulus of elasticity of rigid cellular expanded (hard foam) plastics.

What Standards Apply to Compression of Rigid Plastic Foam?

ASTM D1621 & EN 826. ISO 844 is technically equivalent to EN 826.

Why is Testing Rigid Cellular Plastics Important?

Rigid cellular plastics are manufactured in multiple forms for a variety of applications. They are used in the construction industry as thermal and sound insulation, wall sheathing, waterproofing, and roofing. Walls with rigid cellular plastic can provide a better thermal performance than fiberglass walls. Lightweight polymer is easier to transport and easier to install on site. The most important properties of a cellular plastic product is its resin (polypropylene and polyethylene), its structure (open cell or closed cell), and its density. Common resins include polyethylene (PE) and polypropylene (PP). Polyethylene is the most common resin for containers like cups and lids, while polypropylene is often used in automobile parts.

Important Considerations When Testing Cellular Plastics per ISO 844

Cellular plastics do not behave as perfect elastic materials, and compressive modulus can appear significantly different, depending on variable test conditions, such as test thickness. All data that are to be compared should be obtained using consistent testing conditions. Rigid plastic foam is viscoelastic or time-dependent by its nature so ISO 844 compression tests should not be used for engineering design when an application differs from the load - time scale of the test. Sample dimensional measurement is also important. It's very important to read the actual standard prior to testing. When measuring sample displacement, the standard allows for the measurement using crosshead displacement.

ISO 844 Test Method Summary

The test specimen is located between two parallel compression platens and compressed at a constant rate of displacement until the specimen has deformed to a specified percentage of the specimen's original height. ISO 844 provides cellular materials compressive property data and characterization of hard foam samples . The load-deformation curve is used to calculate the compressive stress at any load (such as compressive stress at proportional-limit load or compressive strength at maximum load) and the effective modulus of elasticity. ISO 844 Test data includes a) compressive strength with deformation properties or b) compressive stress at 10 % relative deformation and c) compressive modulus These tests provide important data for research and development, quality control, and material commercial acceptance or rejection. When measuring axial sample displacement, the standard presumes that the crosshead position crosshead displacement is adequate.

ISO 844 Test Procedure

The test speed in compress mode is 5 mm/min (assuming a 50 mm sample).

ISO 844 Test Machine Requirements

Our universal test machines serve hard foam testing applications and are capable of performing quasi static tension, compression and flexural tests. The machine force capacity should take into account the highest force needed over the lifetime of the equipment. Machines feature a uniform constant rate of extension (CRE), or constant velocity control mode, with a speed range between 1 and 500 mm per minute (0.04 to 20 in/min). Force measurement complies with ISO 7500-1. The majority of rigid hard foam plastics tests can be performed at loads under 2.2 kN (500 lbs).

ISO 844 Fixtures

The test machine is equipped with compression platens sized larger than the largest sample size. Fixed G23 compression platens are placed on the lower platen and upper moving crosshead. The setup does not allow a self aligning platen.