ISO 844 is an ISO test method used to measure compression performance of rigid cellular plastics (rigid polymer foams). It supports product qualification and quality control by generating comparable compressive strength, stress at a defined deformation level, and (when required) compressive modulus values.
If you are not sure which ISO 844 outputs your specification calls for (strength vs. stress at 10% deformation vs. modulus), talk with our team about configuring the right compression setup and reporting package.
ISO 844:2021 — Rigid cellular plastics — Determination of compression properties
ISO 844:2021 defines laboratory methods for determining key compressive properties of rigid cellular plastics under controlled loading conditions. It is commonly referenced for insulation foams and other rigid foamed plastics where compressive behavior is a critical design or acceptance parameter.
| Item | Details |
|---|---|
| Standard | ISO 844:2021 |
| Document type | International Standard (test method) |
| Publication date | 2021-03 |
| Status | Published |
Quick Definition
ISO 844 (Rigid cellular plastics): A compression test method used to determine compressive strength and corresponding relative deformation, compressive stress at 10% relative deformation, and compressive modulus for rigid cellular plastics.
What This Standard Covers
ISO 844 focuses on compressive loading of rigid cellular plastic specimens to quantify how the material resists deformation and load under compression.
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Compressive strength: Peak compressive stress achieved (as defined by the method) and the relative deformation associated with it.
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Compressive stress at 10% deformation: A defined-point value often used for specification limits and batch comparisons.
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Compressive modulus (when required): A stiffness measure derived from the compressive stress/strain relationship, which can drive higher requirements for deformation measurement quality.
Why This Standard Matters in Testing
Rigid foams can show different results depending on cell structure, density, orientation, and how deformation is measured. ISO 844 provides a consistent way to generate compression values that are suitable for internal specifications, supplier qualification, and incoming QA/QC checks.
For equipment selection, the key takeaway is that the intended output matters: a setup that is acceptable for strength or stress-at-10% deformation may need upgrades (especially for deformation measurement) if modulus is required.
Common Materials, Product Types, or Applications Covered
ISO 844 is commonly applied to rigid cellular plastics used in structural and insulation applications where compression performance is part of design verification or acceptance testing.
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Rigid insulation foams and rigid core materials
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Rigid foam blocks, boards, and molded foam components
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R&D studies comparing foam formulations, density grades, or processing conditions
Common Test or Verification Workflow
A typical ISO 844 workflow is built around consistent specimen preparation, conditioning, and controlled compression loading with appropriate measurement and reporting.
Common workflow: prepare specimens from the product form, condition as required by the method/specification, run compression to the required endpoint(s), calculate/report compressive strength and/or stress at 10% relative deformation, and add compressive modulus when specified.
When test results are used for acceptance decisions, it is important to align the reporting requirements (which property, which endpoint, which deformation basis) with the purchasing or product standard that cites ISO 844.
Equipment Commonly Used for This Standard
ISO 844 is typically performed on a universal testing machine (UTM) configured for compression, with fixtures and measurement matched to the required output values.
Common equipment: Electromechanical or servo-hydraulic UTM, compression platens, appropriate load cell capacity, and a controller/data system capable of capturing force and deformation continuously.
Deformation measurement options: Crosshead displacement can be used for many strength or defined-deformation checks, while modulus work often benefits from more direct deformation measurement (for example, a suitable strain measurement approach that reduces system compliance effects).
Specimen support tools: Cutting/machining tools for foam specimens, dimensional measurement tools, and (when required) conditioning capability to bring specimens to a specified atmosphere before testing.
If you are matching a frame capacity, platen size, or deformation measurement package to a specific foam product size and density range, you can request a detailed quote for a compression configuration aligned to your ISO 844 workflow.
How to Read This Designation or Revision
ISO 844:2021 identifies the ISO standard number (844) and the publication year (2021). Many customer specifications, building-product documents, or internal procedures will call out a specific year, and the required calculations or reporting expectations can depend on that cited edition.
Revision sensitivity: Always run the edition stated in the controlling document (purchase spec, product standard, or customer requirement), especially when modulus or defined-deformation reporting is required.
Related Standards, Methods, or Frameworks when useful
ISO 844 results are often used alongside density, dimensional, or thermal property tests for rigid foams. The exact companion methods depend on the product type and the governing product specification.
Practical note: When multiple foam properties are part of a qualification plan, consistent conditioning and specimen orientation across tests can be as important as the test machine configuration.
Talk through your ISO 844 compression setup
If you need help choosing load capacity, platen size, or a deformation measurement approach appropriate for your required ISO 844 outputs, contact our team to discuss your material type, specimen geometry, and reporting targets.