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Home >> Application >> By Standard >> ASTM >> ASTM D >> ASTM D746 Impact Test for Brittleness Temperature of Plastics and Elastomers

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 D746 Test Principle:

The principle is to expose conditioned, clamped specimens (as cantilever beams) to a series of decreasing temperatures in a bath. At each temperature, the specimens are struck by a striker moving at a defined high speed. The brittleness temperature is not a single test result but is calculated statistically as the temperature at which 50% of the specimens would be expected to fail (crack or break completely).

Specific Test Methods

The standard outlines two primary testing contexts:

Full Determination of Brittleness Temperature:

A statistical method requiring testing at multiple temperatures to calculate the precise Tb where 50% failure occurs.

Routine Inspection and Acceptance Procedures:

1), For plastics: Testing a minimum of ten specimens at a specification-defined temperature. The lot is acceptable if no more than five specimens fail.

2), For elastomers: Testing five specimens at a specification-defined temperature. The lot is acceptable if none fail.

Testing equipment for ASTM D746:

Low-temperature brittleness Impact Tester	Cantilever‑mounted pendulum striker; controlled impact speed; 2.0 ± 0.2 m/s (relative velocity between striker and specimen).
Specimen Clamp and Striking Edge Type A	Has specific dimensional requirements, including a striking edge radius of 1.6 ± 0.1 mm and a clearance of 6.35 ± 0.25 mm.
Specimen Clamp and Striking Edge Type B	Has different dimensional requirements, including a clamp jaw radius of 4.0 ± 0.1 mm and a clearance of 3.6 ± 0.1 mm. For both types, the striking edge must move at a linear speed of 2000 ± 200 mm/s at impact.
Torque Wrench	Used to secure specimens in the clamp to a consistent tightness.(0 to 8.5 N·m)
Temperature-Measurement System	Must be accurate to at least ±0.5°C. The use of alternatives like thermocouples is encouraged over mercury thermometers.
Heat-Transfer Medium	A fluid that remains liquid at test temperatures and does not affect the material (e.g., silicone oil, methanol with dry ice).
Temperature Control & Tank	Means to control the bath temperature within ±0.5°C, an insulated tank, and a stirrer.

Test Specimen Information:

Three specimen types are defined, correlating with the clamp type:

Type I (for Type A Apparatus): 6.35 ± 0.51 mm wide by 31.75 ± 6.35 mm long, thickness of 1.91 ± 0.13 mm.

Type II (for Type A Apparatus, "Modified T-50"): T-shaped, thickness of 1.91 ± 0.13 mm. Clamping is critical, with a specified protruding length.

Type III (for Type B Apparatus): 20.0 ± 0.25 mm long by 2.5 ± 0.05 mm wide, thickness of 1.6 ± 0.1 mm.

Preparation: Specimens can be die-punched, cut by hand with a sharp tool, or injection molded. The standard emphasizes that dies must be kept sharp, as dull tools cause nicks that lead to premature failure and unreliable results.

ASTM D746 Test Procedures:

Conditioning: Condition specimens per Practice D618. For studying long-term effects, use Practice D832.

Preliminary Test: Start at an estimated temperature. Test 10 specimens. If all fail, raise temperature 10°C; if none fail, lower it 10°C. Repeat to find the approximate range.

Precise Determination: Test groups of specimens (new for each test) at temperatures in 2°C or 5°C increments. Determine the lowest temperature where none fail and the highest where all fail. At least four test temperatures within this range are required.

Test Execution: Mount specimens in the clamp with a torque wrench, immerse in the bath for 3.0 ± 0.5 minutes, record temperature, and deliver a single impact.

Failure Inspection: Remove and warm specimens. Examine for complete separation or any visible crack. For incomplete breaks, bend the specimen 90° and inspect for cracks.

ASTM D746 Impact Test for Brittleness Temperature of Plastics and Elastomers

Related Test Standard:

ISO 974: Plastics - Determination of the brittleness temperature 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

ASTM D746 Impact Tester for Brittleness Temperature of Plastics and Elastomers

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.

ASTM D746 plastic Brittleness Temperature impact test sample cutter

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

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 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 974 Plastics brittleness temperature impact test –

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

Scope:

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.

Test Procedure:

Specimens are secured in the customer specified specimen holder (A or B) with a torque wrench at 5 in-lb. The specimen holder is lowered into a bath at a specified temperature. The specimens are impacted at 2000 ± 200 mm/s and then examined. The procedure is repeated at a lower temperature until enough data is generated to determine a brittleness temperature. Brittle temperature is the temperature at which 50% of the specimens fail. Brittle failure is defined by ASTM D746 as fracture into 2 or more pieces, or any crack visible to the unaided eye. The specimens can be bent to an angle of 90° and examined for cracks at the bend.

ASTM D2412 Plastic Pipe Deflection Testing by Compression Loading Test –

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 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.

ISO 527-3 Tensile Test on Plastic Film –

ISO 527-3 Plastics - TENSILE PROPERTIES - PART 3: FOR FILMS AND SHEETS

ISO 527-3 is a common international standard that is used to determine the tensile properties of plastic film or sheeting - a plastic test specimen with a thickness less than 1 mm. The tensile properties include tensile strength, yield strength, yield strain, strain at break, and in some cases Young's Modulus. Due to the flexible, delicate nature of these plastic specimens, both gripping and strain measurement can be a challenge.

ISO 527-3 Tensile Test of Plastic Thin Film Sheet

It covers the specimen preparation requirements of thin plastic sheets and films. Thin plastic specimens created with the practices of ISO 527-3 are tensile tested with the practices of ISO 527-1. Thin plastic specimens created in accordance with ISO 527-3 are cut, or punched from a sheet of thin plastic. ISO 527-3 specifies that thin plastic film of sheet specimens must be free from cracks or scratches that will affect the tensile test. ISO 527-3 allows for four specimen geometries that can be used for tensile testing. There are three acceptable dogbone shaped specimens that are acceptable. Specimen created following ISO 527-3 can be used to determine the tensile properties of thin plastic sheets and films including the tensile modulus of elasticity and the tensile energy to break (TEB).

ISO 527-1, ISO 527-2 Tensile Test of Plastics Composites & plastics –

ISO 527-1 Plastics — Determination of tensile properties Part 1: General principles

ISO 527-2 Plastics -- tensile properties -- Part 2: moulding and extrusion

ISO 527-1 covers the test procedures for determining tensile properties of plastics and plastic composites. Tensile properties of plastics that are determined through the practices of ISO 527-1 include tensile strength, tensile modulus and other properties related to stress strain characteristics of plastic materials.

ISO 527-2 specifies the test conditions for determining the tensile properties of moulding and extrusion plastics, based upon the general principles given in ISO 527-1. The methods described in ISO 527-2 are selectively suitable for use with the following range of materials: rigid and semi-rigid thermoplastics moulding, extrusion and cast materials, including compounds filled and reinforced by, for example, short fibres, small rods, plates or granules but excluding textile fibres (see ISO 527-4 and ISO 527-5).

FAQs: ASTM D746 Brittleness Temperature Test

Q1: What is the ASTM D746 test, and what does it measure?

A: ASTM D746 is the Standard Test Method for determining the Brittleness Temperature of Plastics and Elastomers by Impact. It measures the temperature at which these materials exhibit a brittle failure (crack or break) under a specified impact condition. The key result is the Brittleness Temperature (Tb), defined statistically as the temperature at which 50% of the test specimens would probably fail.

Q2: Why is ASTM D746 important for materials?

A:It identifies the minimum safe service temperature in cold environments.

Prevents sudden brittle failure of parts used outdoors, in vehicles, refrigeration, or cold climates.

Supports material selection, formulation development, and quality control.

Provides a widely accepted North American standard for specifications and trade.

Q3: What is a critical precaution noted in the standard?

A: Specimen preparation is paramount. The standard explicitly warns that dull die-cutting tools are a major source of error. Nicks or rough edges on the specimen can initiate cracks, making the material appear more brittle than it truly is, leading to unreliable and non-comparable data. Regular maintenance and honing of cutting dies are essential.

Q4: How long are specimens conditioned at test temperature?

A: 5 minutes in a liquid bath

10 minutes in a gas cooling chamber

This ensures the specimen reaches full thermal equilibrium.

Q5: Can ASTM D746 be used for rubber?

A: It can be used for elastomers, but for traditional vulcanized rubber, ASTM D2137 is often more appropriate. ASTM D746 is mainly for plastics and flexible polymers.

Q6: What is the difference between Type A and Type B fixtures?

A: They have slightly different clamping and impact geometries.

Type A: Traditional fixture

Type B: Designed to align closer to ISO 974 for better cross‑standard comparison

Q7: What is the difference between ASTM D746 and ISO 974?

A: Both measure low‑temperature brittleness by impact, but they differ in specimen details, fixture dimensions, conditioning, and reporting. Results are similar but not always directly interchangeable.

Q8: What materials are commonly tested with ASTM D746?

A:PVC, PE, PP, flexible plastics

TPE, TPO, thermoplastic elastomers

Films, sheets, molded components used in cold conditions.

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