Foam testing

The main purpose of flexible cellular foam is to provide comfort. Its prominent characteristics are damping and insulation. Engineered polyurethane foams are used in mattresses, for furniture and vehicle cushions, and in a wide variety of other applications requiring thermal and acoustic insulation. Additional applications for flexible cellular foams include filters, packaging, seals, and sponges, for which other polymers such as polyethylene are also used.

Flexible foam testing procedures are established in a series of ISO standards including ISO 2439 (indentation hardness), ISO 3386 (compression stress value), ISO 1798 (tensile strength), ISO 8067 (tear strength), ISO 3385 (fatigue by constant-load pounding), and ASTM D3574 (collective standard). The cushions and backrests for vehicle seats are tested according 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.

Rigid cellular plastics are used in construction and refrigeration for thermal insulation, in homes for impact sound insulation, and in aircraft and wind turbines as a core material for sandwich constructions and core composites or in shop fitting as a lightweight and rigid material with cover layers.

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.

The test methods used for rigid foam testing are also based on the area of application. The measurement of thermal properties and fire behavior play an important role. Mechanical foam tests focus on compression and shear tests, however 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

ZwickRoell is a global leader in testing of flexible cellular foams and rigid cellular plastics. Our c-frame materials testing machine cLine is ideal for tests on large foam pieces. Universal testing machines including the zwickiLine and ProLine can be used when testing smaller standard specimens. Our testXpert software for cellular foam material testing covers every requirement for determination of the compressive stress value, indentation hardness, compression properties, tensile strength, and tear growth behavior. Standard test programs are fully predefined according to the 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 electrodynamic testing machine for high cycle fatigue tests. This machine is designed for high test speeds and fast direction changes, making it ideal for the performance of high cycle fatigue tests on standard specimens. However, it can also be used for static tests to determine characteristics such as compressive stress value, indentation hardness and reduction in thickness and hardness.

In addition, ZwickRoell supplies devices for specimen preparation, precision scales for bulk density measurement, rebound resilience testers, and Shore hardness testing instruments.