ASTM tests brittle temperature

Low Temperature Brittleness. Brittleness temperature is the temperature at which polyethylene becomes sufficiently brittle to break when subjected to a sudden blow. Because some polyethylene end products are used under particularly cold climates, they must be made of a polymer that has good impact resistance at low temperatures namely, polymers with high viscosity, lower density, and narrow molecular weight distribution. ASTM D746 is used for this test. 

DYNH. ASTM brittle temperature test No. D-46-44T was used in making these measurements. Statex 125 carbon black is manufactured by Columbian Carbon Co., New York, N. Y. 

ASTM D746-98e Standard Test Method for Brittleness Temperature of Plastics and Elastomers by Impact... 

As can be observed in this comparison, a variety of hardnesses, low temperature properties and elongations can be obtained, depending upon the choice of phthalate ester employed. Moreover, by comparing plasticizers such as butyl benzyl phthalate (BBP) to di-2-ethyl hexyl phthalate (DOP) one sees the higher solvating power of the BBP, reflected in the lower value of minimum flux femperature. So, for formulations where rapid plasticization is required, BBP is a good choice. However, the brittleness temperature for BBP formulations, based on the standard ASTM D-746 test protocol, is expected to be higher than that for DOP. 

There are various methods for performing this test. In the ASTM standard, a specimen comprised of a loop of film is subjected to a hammer impact load. The test is repeated over a series of temperatures and the impacted specimens are examined visually to determine the temperature below which failure occurs in a brittle mode. Another type of test, which evaluates brittleness temperature in a similar manner, utilizes a specimen of film that is clamped onto a table over an oval opening and inflated with air until failure. Because of the shape of the opening, this is known as a racetrack test. 

In the test for brittleness temperature (ASTM D 746), a small rectangular strip is clamped in a holder at one end and cooled to a predetermined temperature in a chilled liquid bath. The specimen is then given a sudden sharp blow by a solenoid-actuated striking arm. If the specimen does not fracture, the temperature of the liquid bath is lowered, and the process is repeated until the specimen breaks when struck. 

In the temperature retraction test (ASTM D 1329), the test specimen is stretched to a specified elongation and then frozen at -70°C. Then it is gradually warmed until it begins to retract toward its original unstretched dimensions. The temperature at which the specimen retracts by 10 percent correlates with the brittleness temperature. 

Low-temperature flexibility All plastics that are flexible at room temperature become less so as they are chilled, finally becoming brittle at some low temperature. This property is often measured by torsional tests over wide ranges of temperature, from which apparent moduli of elasticity are calculated. Some relevant ASTM tests are D 1043, D 3295, D 3296, D 3374... 

Thermal properties n. All properties of materials involving heat or changes in temperature. In Section 08 of ASTM s Annual Book of Standards ( Plastics ), tests listed under Thermal Properties include many properties, from brittleness temperature, coefficient of expansion, deflection temperature, etc., to heat of fusion, glass-transition temperature, thermal conductivity, heat capacity, mold shrinkage, flammability, and many more. 

Brittleness temperatures are an assessment of the sub-zero temperature at which the material becomes brittle. A good or excellent rating indicates a low brittle temperature, i.e., it is serviceable at low temperatures. A poor rating indicates a high brittle temperature, i.e., it only has a limited sub-zero range of usefulness. An impact test for the measurement of brittleness is described in ASTM D746 [13]. 

Brittleness point TR test Low temperature brittleness check ASTM D1329 [140] Gibitre, Italy available from Negretti Automation and ATS FAAR Code Nos. 10.2900 10.29005 10.12010... 

ASTM D746, Test method for brittleness temperature of plastics and elastomers by impact, 2004. 

Impact Resistance n (1) Ability of a coating to resist a sudden blow. Ability to resist deformation from impact. (2) The relative durability of plastics article to fracture under stresses applied at high speeds. A widely used ASTM impact test, www.astm.org, employs the Izod pendulum striker swung from a fixed height to strike a specimen in the form of a notched bar mounted vertically as a cantilever beam. The Charpy tester, an alternative in D 256, uses a specimen in the form of a horizontal beam supported at both ends. ASTM lists some several different impact tests for plastics and plastics products. See also Brittleness Temperature, Drop-Weight Test, Free-Falling-Dart Test, and... 

Figure 3-12. Typical specimen clamp for brittleness temperature test. (Reprinted with permission of ASTM.)...

Impact strength is usually only determined for plastics and hard elastomer compounds (i.e., those in the D durometer hardness range), where the impact resistance of the material in actual service is important. Soft elastomer compounds will bend, not break, on impact unless they have been cooled below their brittleness temperature. Several types of impact testers and test methods are available. Basically, they all measure the energy required to break a test specimen in a single sharp blow, and can be performed over a temperature range from -70 to +120°C (-94 to +248°F). The most widely used tests are Izod Impact and Charpy Impact both procedures are given in ASTM D-256. 

FIGURE 10.2 Mechanical failure tests (a) tensile test on dumbbell specimen (b) tensile test on ring specimen (c) notched crescent and trousers tear specimens (d) Izod impact test machine (Data from HaUinan, A. J., Jr., J. Qual. Tech., 25, 85, 1993) (e) motor-driven brittleness temperature tester. (Data from Book of Standards, ASTM, Baltimore, MD, 1958, 286,356.)... 

Heat Distortion Test. Two remaining bars from the cleavage tests are used to determine heat distortion temperature in accordance with ASTM D-621 test methods. These thermal-mechanical tests are necessary to determine whether a brittle resin has been truly toughened or whether it has been merely flexibilized. The morphology of the resin also effectively describes a true toughening situation and can aid immeasurably in explaining departures from true toughening. 

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