ISO 899-2 is an ISO test method for measuring flexural creep of plastics using a three-point loading (freely supported beam, mid-span load) setup. It is commonly used when teams need time-dependent bending/deflection behavior for product design, material qualification, or comparative performance checks.
This standard is most relevant for rigid and semi-rigid plastics, including non-reinforced, filled, and fibre-reinforced materials, when long-term deformation under sustained flexural stress is a concern. If you need help matching your material and time/temperature conditions to an appropriate creep setup, talk with our team.
ISO 899-2 — Plastics — Determination of creep behaviour — Part 2: Flexural creep by three-point loading
ISO 899-2 describes a controlled way to apply a constant flexural load in a three-point configuration and track how a plastics specimen deforms over time under specified conditioning and environmental conditions.
The intent is typically to generate creep curves or time-dependent flexural deformation data that can support engineering evaluation, R&D comparisons, and internal material performance benchmarks.
Quick definition
Document type: Test method (creep test in flexure).
What it measures: Time-dependent flexural deformation (creep) under sustained three-point bending load.
Common outputs: Deflection (or strain/displacement) versus time under defined stress and environment.
What this standard covers
ISO 899-2 focuses on flexural creep using a simple beam supported at two points and loaded at the midpoint (three-point loading). The method is applied to standard specimens produced by moulding or machining from sheet or moulded articles.
The standard is commonly used for rigid and semi-rigid plastics, including filled and fibre-reinforced plastics. Because fibre orientation can influence results, fibre-reinforced materials may require added care in specimen selection and interpretation.
Why this standard matters in testing
Many plastic parts see sustained bending stresses in service (fixtures, housings, clips, covers, structural panels, and load-bearing components). Flexural creep testing helps quantify how deflection can grow over hours, days, or longer under steady load.
Because creep behavior is sensitive to specimen preparation, dimensions, and environment, aligning your lab setup with the cited ISO 899-2 edition is important when you need meaningful comparisons between materials, suppliers, or process conditions.
Common materials, product types, or applications covered
ISO 899-2 is most often applied to rigid and semi-rigid thermoplastics and thermosets where long-term deformation under bending load is a design concern.
Common use cases: Material screening for creep resistance, qualification of moulded vs. machined stock, comparing filled vs. unfilled grades, and checking the effect of temperature/humidity exposure on long-term stiffness retention.
The method is not always appropriate for rigid cellular plastics; separate flexural standards for cellular materials may be more suitable depending on the product structure.
Common test or verification workflow
Flexural creep programs are often planned around a specific application stress, a target duration (short-term screening vs. longer-term evaluation), and a controlled environment.
Common workflow: Condition specimens as required, apply a defined three-point flexural load, measure deflection (or equivalent displacement/strain) over time, and report creep behavior under the stated temperature and humidity conditions.
Equipment commonly used for this standard
ISO 899-2 typically points to a controlled three-point bending creep setup capable of holding a constant load for extended periods while measuring deflection accurately.
- Flexural creep frame or loading rig: Three-point bending fixture with stable supports and a mid-span loading nose designed for long-duration loading.
- Load application system: A constant-load arrangement (commonly dead weights or an equivalent constant-force mechanism appropriate for creep testing).
- Deflection measurement: Displacement transducer or extensometry appropriate for long-term drift control and the required resolution.
- Environmental control: Temperature (and, when required, humidity) conditioning via an environmental chamber or controlled enclosure.
- Data acquisition: Long-duration logging with time-stamped measurements, suitable sampling intervals, and stable sensor excitation.
When you are specifying a creep rig, chamber size, sensors, or long-term data logging, you can request a detailed quote for an equipment package matched to your duration and environment requirements.
How to read this designation or revision
ISO 899-2 identifies the Part 2 method within the ISO 899 series for determining creep behaviour of plastics.
Year suffix: When cited as ISO 899-2:2024 (or another year), the year indicates the published edition being referenced. Test conditions, reporting expectations, and instrumentation expectations can vary by edition, so purchase specifications and lab instructions should cite the same edition used for acceptance.
Known recent edition: ISO 899-2:2024 is Edition 3. Earlier editions (such as ISO 899-2:2003) may still appear in legacy specifications.
Related standards, methods, or frameworks
ISO 899-2 is part of a broader ISO approach to plastics creep testing and is often referenced alongside companion documents depending on whether the required loading mode is tensile or flexural, and how materials are defined.
- ISO 899-1: Tensile creep testing in the same series (commonly referenced when axial loading is the design driver).
- ISO 472: Plastics terminology commonly referenced for material definitions.
- ISO 1209-1 / ISO 1209-2: Flexural testing references often used when rigid cellular plastics are involved.
Get help selecting a flexural creep test setup
If you are planning ISO 899-2 testing and need a system configured around your target load range, test duration, and environmental conditions, you can ask for a quote for a complete flexural creep setup (fixture, load application, sensors, chamber integration, and data logging).