Information on the most widely used ASTM standards within the materials testing industry
ISO 604 Plastics -- Determination of compressive properties
ISO 604 specifies a method for determining the compressive properties of plastics under defined conditions. It is used to investigate the compressive behavior of test specimens and to determine key mechanical properties such as compressive strength, compressive modulus, and other aspects of the compressive stress/strain relationship. Specimen length is adjusted to avoid buckling that would distort results.
Test Principle:
A test specimen is compressed along its major axis at a constant speed until the specimen fractures or until the load or the decrease in length reaches a predetermined value. The load sustained by the specimen is measured throughout this procedure.

Specific Test Methods
Only one core axial compression method is defined, with adjustable parameters (speed, specimen dimensions) for different materials. It is suitable for:
Rigid/semi‑rigid thermoplastics (unfilled, filled, short‑fiber‑reinforced).
Rigid/semi‑rigid thermosets (filled/reinforced).
Thermotropic liquid‑crystal polymers (fiber length ≤7.5 mm after processing).
Not suitable for textile‑fiber composites, laminates, rigid foams, or sandwich structures.
Key Parameters and Stipulations
Test Speeds: Ranging from 1 to 20 mm/min, depending on the material and the property being measured (e.g., 1 mm/min for modulus, 5 mm/min for yielding materials) .
Buckling Prevention: The specimen's length-to-thickness ratio is strictly regulated to prevent buckling, which would compromise the accuracy of the results.
Platens must be fully parallel and aligned; use spherical seat to eliminate bending stress.
Specimen ends must be flat, smooth, and perpendicular to the longitudinal axis.
Test speed, conditioning, and dimensions must be strictly controlled for comparable results.
Machine compliance shall be corrected for accurate modulus calculation.
Results are invalid if buckling occurs before the intended failure mode.
ISO 604 Compression Test Specimen Information:
| Preferred dimensions | Modulus test: 50 mm × 10 mm × 4 mm Strength test: 10 mm × 10 mm × 10 mm Cylindrical: Ø10 mm × 25 mm (common) |
| Shape | Right prism, cylinder, or tube; flat, parallel, smooth end faces (perpendicularity ≤0.025 mm) |
| Quantity | At least five specimens are required for isotropic materials, and ten (five in each principal direction) for anisotropic materials . |
| Preparation | Specimens can be directly compression/injection molded or machined from sheets or finished products according to standards like ISO 293, ISO 294-1, or ISO 2818. The ends must be smooth, flat, and parallel . |
ISO 604 Plastic Compression Test required Testing Equipment:
| Universal Test Machine | Must comply with ISO 5893. Recommend UnitedTest Brand compression testing machine or universal testing machine. It should be capable of maintaining constant test speeds (ranging from 1 mm/min to 20 mm/min) with high tolerance . |
| Parallel compression platens | Upper platen with spherical seat to ensure full contact; alignment ≤±0.05 mm to avoid bending stress. |
| Extensometer | Optional for modulus, High‑precision deformation measurement |
| Dimension measuring tools | Micrometers or equivalent instruments to measure the dimensions of the test specimens accurately. |
Key Test Procedures:
The test procedure involves several critical steps:
Conditioning: Specimens must be conditioned in a standard atmosphere (preferably 23/50) as specified in ISO 291 .
Dimension Measurement: Measure the width, thickness, and length of the specimen to calculate the mean cross-sectional area .
Setup: Place the specimen between the compression plates, ensuring perfect alignment. A slight preload may be applied to avoid an initial curved region on the stress/strain diagram .
Speed Selection: Select the appropriate test speed based on whether you are measuring modulus (slower speeds, e.g., 1 mm/min) or strength/yield (faster speeds, e.g., 5 mm/min) .
Execution: Compress the specimen at the constant selected speed until fracture or the specified strain limit is reached. Record the force and displacement continuously .
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| Typical stress-strain curve ISO 604 compression |
Industries Benefiting from ISO 604 Compliant Testing:
Automotive: Ensuring components can withstand stresses under load.
Aerospace: Certifying materials for safety and performance in extreme conditions.
Consumer Goods: Guaranteeing that everyday products are durable and safe.
Construction: PVC profiles, pipe fittings, rigid components.
Related Test Standard
| ASTM D695 | Standard Test Method for Compressive Properties of Rigid Plastics |
| ASTM D1621 | Standard Test Method for Compressive Properties of Rigid Cellular Plastics |
| ISO 7616 | Cellular plastics, rigid-Determination of compressive creep under specified load and temperature conditions |
| ISO 844 | Rigid cellular plastics — Determination of compression properties |
| ISO 7743 | Rubber, vulcanized or thermoplastic; determination of compression stress-strain properties |
| TCVN 11993 | Plastics. Determination of compressive properties |
Related products and device
Related Standard
ASTM D695: Standard Test Method for Compressive Properties of Rigid Plastics
ASTM D695 test covers the determination of the mechanical properties of unreinforced and reinforced rigid plastics, including high-modulus composites, when loaded in compression at relatively low uniform rates of straining or loading. Test specimens of standard shape are employed. This procedure is applicable for a composite modulus up to and including 41,370 MPa (6,000,000 psi).
ASTM D2412: Standard Test Method for Determination of External Loading Characteristics of Plastic Pipe by Parallel-Plate Loading
Plastic pipe compression test, or pipe ring stiffness tseter is a testing standard used to determine the stiffness and load deflection of plastic pipe. This summary is intended to help you understand the basic procedure and equipment required to complete this test with accuracy.
ASTM D2412 test method covers the determination of load-deflection characteristics of plastic pipe under parallel-plate loading.
ASTM D3410 Shear Loading compression Test Method for Compressive Properties of Polymer Matrix Composite Materials with Unsupported Gage Section.
ASTM D3410 test method determines the in-plane compressive properties of polymer matrix composite materials reinforced by high-modulus fibers. It is applicable to composites made from unidirectional tape, wet-tow placement, textile (for example, fabric), short fibers, or similar product forms. Some product forms may require deviations from the test method.
ASTM D3410 is designed to produce compressive property data for material specifications, research and development, quality assurance, and structural design and analysis. Factors that influence the compressive response and should therefore be reported include the following: material, methods of material preparation and layup, specimen stacking sequence, specimen preparation, specimen conditioning, environment of testing, specimen alignment and gripping, speed of testing, time at temperature, void content, and volume percent reinforcement.
ISO 14126 Compression test Fibre-reinforced plastic composites — Determination of compressive properties in the in-plane direction
The ISO 14126 and ASTM D3410 standards describe the shear loading compression test on composites. The objective of this standard test method is the determination of compressive properties in laminate planes.
For this method, the compression force is transmitted via shear forces to the specimen, which is secured in the test fixture and usually includes cap strips. Homogeneous stress distribution is achieved if there is sufficient grip-to-grip separation in the unsupported center area of the specimen.
One of the benefits provided is axial guidance of the specimen during the test, as well as the elimination of force application via the end faces. This eliminates the need for high-precision preparation of the specimen end faces.
ISO 604 Compression Test for Plastics – Concise FAQs
Q1: Why is the ISO 604 test important for plastics?
A: The ISO 604 test provides essential data on a plastic’s compressive strength, modulus, and stress‑strain behavior. This information is critical for engineers to design safe, load‑bearing plastic components (e.g., in automotive, aerospace, construction), for manufacturers to compare material performance, and for quality control to ensure raw materials meet specifications.
Q2: Which materials can be tested with ISO 604?
A: It applies to rigid and semi‑rigid thermoplastics (including filled/reinforced compounds), thermosets, and thermotropic liquid‑crystal polymers. It is not suitable for textile‑fiber‑reinforced composites, rigid foams, or sandwich structures.
Q3: Can small specimens be used if material is limited?
A: Yes, Annex A permits two small specimen types (e.g., 6 mm or 35 mm long). Results may differ from standard specimens, so their use must be agreed upon and reported.
Q4: What must be included in the test report?
A: The report must state the ISO 604 reference, specimen type/speed, material details, specimen dimensions, preparation method, orientation (if anisotropic), number of specimens, conditioning/test atmosphere, machine/extensometer details, slip treatment, individual and mean results, and any rejected specimens.
Q5: Why use a spherical seat on the upper platen?
A: To automatically align the platen with the specimen, eliminate bending stress, and ensure pure axial compression.
Q6: When is a test result invalid?
A: If the specimen bucks (bends) before yielding or fracturing; if misalignment causes bending failure.
Q7: How to prevent specimen buckling?
A: Shorten the specimen length; use proper length‑to‑width ratio; ensure perfect alignment.
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