Home >> Application >> By Standard >> ISO >> ISO 1 ~ 4999 >> ISO 974 Plastics brittleness temperature impact test

ISO 974 Plastics brittleness temperature impact test

Share:

ISO 974 Plastics -- Determination of the brittleness temperature by impact


Brittleness temperature is the temperature at which 50% of the tested specimens exhibit brittle failure at specified impact conditions. It is utilized primarily for plastics and elastomers. ISO 974 defines a test method to determine the temperature at which plastics (particularly those not rigid at room temperature) exhibit brittle failure under specified impact conditions. The standard establishes the Brittleness Temperature (T₅₀), defined as the temperature at which there is a 50% probability of failure for the test specimens.


Test Principle: 

The test principle involves supporting test specimens as cantilever beams and immersing them in a precisely controlled heat-transfer medium. After conditioning for a specified time at a set temperature, the specimens are impacted by a single swing of a striking edge at a constant speed. By testing a sufficient number of specimens at different temperatures, the temperature at which 50% of the specimens fail is determined statistically as the brittleness temperature.


Thermal Equilibration: Specimens are immersed in a cooled bath and held at a set temperature for a defined period (usually 5 min in liquid, 10 min in gas) to ensure uniform temperature.

Controlled Impact: A cantilevered specimen is struck by a pendulum striker at 2.0 ± 0.2 m/s.

Failure Assessment: Visually inspect for cracking or complete fracture (failure) after impact.

Statistical Calculation: Test at increasing/decreasing temperatures. Plot failure rate vs. temperature to determine T₅₀ (the temperature with 50% probability of failure).


Test Equipment used for ISO 974: 

Low Temperature Brittleness Impact Tester

Consists of a clamping device and a striking edge. 

Key dimensions are strictly defined

Radius of striking edge: 1.6 mm ± 0.1 mm.

Radius of lower jaw of clamp: 4.0 mm ± 0.1 mm.

Distance from impact point to clamp: 3.6 mm ± 0.1 mm.

Clearance between striking edge and clamp: 2.0 mm ± 0.1 mm.

Test speed at impact: 200 cm/s ± 20 cm/s.

ISO 974 Plastics brittleness temperature impact test

Temperature-Measuring SystemMust be accurate to within ±0.5°C and placed as near to the specimen as possible.
Heat-Transfer MediumA liquid or gas (preferably liquid, e.g., a methanol/dry-ice mixture) that remains fluid at the test temperature, does not affect the material, and is maintained at the test temperature within ±0.5°C.
Insulated Tank and StirrerTo contain the medium and ensure uniform temperature.



ISO 974 Test Specimen Information: 

Dimensions: 20.00 mm (±0.25 mm) long by 2.50 mm (±0.05 mm) wide by 2.0 mm (±0.1 mm) thick.

Preparation: Specimens must be cut (not die-cut) from a test sheet using a razor blade or other sharp tool in a single, smooth stroke to ensure clean edges and reproducible results. Dull cutters can induce premature failure.

Quantity: Minimum 10 specimens per temperature level; typically tested across 5–7 temperatures for statistical T₅₀ calculation

It is essential that the specimens be prepared in a reproducible way. A razor blade or other sharp tool shall be used to cut the specimens, preferably in a single smooth stroke. Die-cut specimens are not recommended. Although it is possible to prepare satisfactory specimens by hand, it is strongly recommended that an automatic method be used. Whatever method is used, it is essential that the cutter be inspected frequently and maintained. Sharp cutters must be used in the preparation of specimens for this test if reliable results are to be obtained.

ISO 974 Plastics brittleness temperature impact testISO 974 Plastics brittleness temperature impact test


General ISO 794 Test Procedures:

Prepare Specimens: Mold/cut to standard dimensions; create notches if required.

Approximate Temperature Range Finding: Start at a temperature where 50% failure is expected. Test a minimum of 10 specimens. If all fail, increase the bath temperature by 10°C; if none fail, decrease it by 10°C. Repeat with new specimens until the approximate range is found.

Precise T₅₀ Determination: Conduct tests at four or more temperatures within the range that yields failure rates between 10% and 90%. Use uniform temperature increments (e.g., 2°C or 5°C) and new specimens for each test.

Specimens are clamped, immersed, conditioned for 3.0 min ± 0.5 min (liquid) or 20 min ± 0.5 min (gas), and then impacted.

Failure is defined as complete separation into two or more pieces, or any crack visible to the unaided eye. For incomplete separation, the specimen is bent 90° and examined for cracks. 

Result Calculation: 

T₅₀ is determined either by:

Graphical Method: Plotting % failure vs. temperature on probability paper and reading the temperature at the 50% intercept.

Calculation Method: Using the formula provided in the standard.



ISO 794 Test Application & Importance for Plastic Materials: 

Application: Primarily used for specification purposes, quality control, and material comparison. It helps predict the low-temperature behavior of plastics in applications involving flexing or impact.

Importance: The test is crucial because it simulates a material's transition from a ductile to a brittle state upon cooling under specific impact conditions. 

Knowing the brittleness temperature helps engineers:

Select materials suitable for low-temperature environments.

Predict the lower temperature limit for safe application where impact resistance is needed.

Ensure batch-to-batch consistency in material production.


Related standard: 

ASTM D746: Standard Test Method for Brittleness Temperature of Plastics and Elastomers by Impact.

NS 9508: Plastics - Determination of the brittleness temperature by impact;

GOST 16782: Plastics. Determination of the brittleness temperature by impact;

UNE 53120: Plastic. Determination of the brittleness temperature by impact.

GB/T 5470: Plastics.Determination of the brittleness temperature by impact.

KS M 3059: Test method for brittleness temperature of plastics and elastomers by impact.

Related products and device

ISO 794 Plastics brittleness temperature impact tester

Rubber low-temperature brittleness testing machine is to determine the highest temperature of vulcanized rubber under specified conditions when the sample is damaged by impact. Follow the standard ASTM D2137 ASTM D746; ISO 812; ISO 974.

ISO 794 Plastics brittleness temperature impact test specimen cutting device

Electric sample punching machine is a sample preparation device designed based on the punching principle, specifically developed for preparing standard samples of sheet-like, film-like, and thin plate materials.

Related Standard

ASTM D746 Impact Test for Brittleness Temperature of Plastics and Elastomers

ASTM D746: Standard Test Method for Brittleness Temperature of Plastics and Elastomers by Impact


ASTM D746 test method establishes the temperature at which 50 % of the specimens tested would probably fail when subjected to the conditions specified herein. The test provides for the evaluation of long-time effects such as crystallization, or those effects that are introduced by low-temperature incompatibility of plasticizers in the material under test. Plastics and elastomers are used in many applications requiring low-temperature flexing with or without impact. Use data obtained by this method to predict the behavior of plastic and elastomeric materials at low temperatures only in applications in which the conditions of deformation are similar to those specified in this test method. This test method has been found useful for specification purposes, but does not necessarily measure the lowest temperature at which the material is suitable for use.

ASTM D2137 Rubber Brittleness Point Test of Flexible Polymers and Coated Fabrics

ASTM D2137: Standard Test Methods for Rubber Property--Brittleness Point of Flexible Polymers and Coated Fabrics


ASTM D2137 test method is used to evaluate the brittleness of rubber materials, or rubber coated fabrics, when exposed to low-temperature flex with an impact under specified conditions of striker speed. ASTM D2137 tests performed will be used to determine the lowest temperature at which rubber compounds will not show fractures or coating cracks when exposed to specified impact conditions.

ISO 812 Low-temperature brittleness Impac Test of Rubber, vulcanized or thermoplastic

ISO 812:2017 specifies a method for determining the lowest temperature at which rubber materials do not exhibit brittle failure or the temperature at which half of the test pieces used in a test fail when impacted under specified conditions.

The temperatures thus determined do not necessarily relate to the lowest temperature at which the material can be used since the brittleness will be affected by the conditions of test and especially by the rate of impact. Data obtained by this method are, therefore, intended to be used to predict the behaviour of rubbers at low temperatures only in applications in which the conditions of deformation are similar to those specified in the test.


ASTM D790 Bending Test Flexural Properties of Unreinforced and Reinforced Plastics

ASTM D790: Standard Test Methods for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials


ASTM D790 test methods are used to determine the flexural properties of unreinforced and reinforced plastics, including high modulus composites and electrical insulating materials utilizing a three-point loading system to apply a load to a simply supported beam (specimen). The method is generally applicable to both rigid and semi-rigid materials, but flexural strength cannot be determined for those materials that do not break or yield in the outer surface of the test specimen within the 5.0 % strain limit.

ASTM D6110 Plastic Charpy Impact Test of Notched Specimens

ASTM D6110: Standard Test Method for Determining the Charpy Impact Resistance of Notched Specimens of Plastics


ASTM D6110 test method is used to determine the resistance of plastics to breakage by flexural shock as indicated by the energy extracted from standardized pendulum-type hammers, mounted in standardized machines, in breaking standard specimens with one pendulum swing. This test method requires specimens to be made with a milled notch. The notch produces a stress concentration which promotes a brittle, rather than a ductile, fracture. The results of this test method are reported in terms of energy absorbed per unit of specimen width.


The tests require specimens made with a milled notch, hence the test is often referred to as the “notched bar impact test”. In both the Charpy and Izod Tests, the notch produces a stress concentration which promotes a brittle, rather than a ductile, fracture.

ASTM D638 Tensile Testing method for Properties of Plastics

ASTM D638 : Standard Test Method for Tensile Properties of Plastics


ASTM D638 specifies methods for testing the tensile strength of plastics and other resin materials and for calculating their mechanical properties, and outlines accuracy requirements for the test frames and accessories used. This test method uses dumbbell-shaped specimens with either a  25 mm or 50 mm gauge length.

Frequently Asked Questions (FAQs) about ISO 794 test standard

Q1: What exactly is measured by the ISO 974 test?

A1: The ISO 974 test determines the Brittleness Temperature (T₅₀) of a plastic material. This is defined as the temperature at which there is a 50% probability that a test specimen will fail (crack or break completely) under a specified impact condition.


Q2: How does the test work in simple terms?

A2: Small, bar-shaped specimens are clamped at one end (like a diving board) and immersed in a cooled liquid. After being held at a set temperature for 3 minutes, a metal striker hits them at a very high, constant speed (200 cm/s). The process is repeated at different temperatures with new specimens. The temperature at which half of the tested specimens break is reported as the brittleness temperature.


Q3: What do the test specimens look like, and how are they made?

A3: Specimens are small bars: 20.00 mm long, 2.50 mm wide, and 2.0 mm thick. They must be cut cleanly from a sheet of material using a very sharp blade (like a razor) in a single stroke. The standard strongly advises against using a dull die to punch them out, as nicks or rough edges can cause premature failure and give incorrectly high (worse) brittleness temperatures.


Q4: Does this test apply to all plastics?

A4: Primarily, it is intended for plastics that are not rigid at normal room temperature (e.g., many flexible or semi-rigid thermoplastics like polyethylene or plasticized PVC). A supplementary method using notched specimens can be used to test rigid materials or to get a failure signal at a higher temperature.

< Previous: ISO 812 Low-temperature brittleness Impac Test of Rubber, vulcanized or thermoplastic

> Next: ISO 1133 Test Method of Determination melt mass-flow rate (MFR, MVR)

Require More Customized Solutions?

We offer customization to meet your specific needs. Our expert team will collaborate with you to develop the perfect product for you
Customize Now

Beijing United Test Co., Ltd.