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Testing of Hard and Soft Polymer Foams

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Flexible Foam

First and foremost, flexible foam provides comfort. Its prominent characteristics are damping and insulation. Engineered foams made of PU are used in mattresses, for furniture and vehicle cushions, and in a wide variety of other applications requiring thermal and acoustic insulation. Additional applications that use flexible foam are filters, packaging, seals, and sponges. Other polymers such as PE are also used in these applications.

The test methods are defined in a number of ISO standards and in ASTM D3574. The cushions and backrests for vehicle seats are tested to company standards, which are defined by the automobile industry's OEMs. There are special test methods not found in international standards for aging tests.

ZwickRoell is a global leader in this type of testing. The C-frame testing machines make testing of large foam pieces easy. Standard machines can be used to test smaller standard specimens. The testXpert software for foam testing meets all requirements for determining the compressive stress value, indentation hardness, compression properties, tensile strength, and tear growth behavior. Standard test programs are predefined to comply with individual standards. This means you can be sure that your test sequences are correct and your results are evaluated with accuracy.

ZwickRoell offers a special electro-mechanical testing machine for fatigue tests. This durable machine is designed for high test speeds and fast directional changes. That is why this type of machine is optimal for fatigue tests on standard specimens, however it can be also used to perform static tests to determine compression strength, indentation hardness, and thickness and hardness loss.

Furthermore, ZwickRoell supplies devices for specimen preparation, bulk density measurement, rebound resilience, and Shore hardness.

Hard Polymer Foam

Hard polymer foam is used in construction and in refrigerators as insulation, in houses for sound-proofing, and in airplanes and wind turbines as a core material for sandwich-structure composites.

It is also used in packaging technology. This type of foam is an expanded foam, meaning a foamed polymer. Hard foams made of polyurethane (PU), polystyrene (EPS), polyvinyl chloride (PVC), polypropylene (EPP), and phenolic resin (PF) are also widely used. The foams are produced as closed-cell or open-cell foam, or as integral foam with a solid exterior and a foamed cellular core.

For these materials, the test methods are also based on the area of application. The measurement of thermal properties and fire behavior play an important role. Compression and shear tests are the predominant mechanical test methods, while tensile properties can also be of interest.

Important test standards for determining mechanical material properties include: 

  • ISO 844 - Determination of compression properties
  • ISO 1922 - Determination of shear strength
  • ISO 1926 - Determination of tensile properties
  • EN 1607 - Determination of tensile strength perpendicular to faces
  • ISO 1209-1 - General bending test
  • ISO 1209-2 - Determination of flexural strength and apparent flexural modulus of elasticity
  • ISO 7616 - Determination of compressive creep under specified load and temperature conditions

Indentation hardness

Among others, DIN 53579-1, ISO 2439, ASTM D3574
Indentation hardness of molded foams such as vehicle cushions, mattresses, etc. to DIN 53579-1, and in materials testing to ISO 2439, ASTM D 574.
to Indentation hardness

Compression stress value

ISO 3386
Pressure resistance that a defined specimen under specified environmental conditions applies to a defined whole-surface compression.
to Compression stress value

Tensile properties/tear strength

ISO 1798 and ISO 8067
Tests on soft foam to ISO 1798 and ISO 8067 and factory regulations
to Tensile properties/tear strength

Fatigue test

ISO 3385
Long-term behavior of foam under constant mechanical load to ISO 3385, ASTM D3574
to Fatigue test

Compression tests on hard foam

ISO 844, ASTM D1621, EN 826
Compressive strength, maximum compressive deformation, compression modulus describe the short-term deformation behavior under load.
to Compression tests on hard foam

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