ASTM D746 Plastics and Elastomers Brittle Test

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

The primary purpose of ASTM D746 is to establish the temperature at which 50% of the specimens tested would probably fail when subjected to specific impact conditions. This information is vital for:

  • Material Selection: Ensuring materials can withstand low-temperature environments without failure.

  • Quality Control: Verifying that materials meet required specifications for brittleness temperature.

  • Product Development: Designing products that maintain integrity under low-temperature conditions.

Test Procedure Overview

  1. Sample Preparation: Specimens are prepared in standardized sizes and shapes, typically Type I (6.35 mm x 31.75 mm x 1.91 mm thick) or Type III (20 mm x 2.5 mm x 2.0 mm thick).

  2. Conditioning: Specimens are conditioned under standard laboratory conditions before testing.

  3. Testing:

    • Specimens are secured in a holder and immersed in a bath at a specified temperature.

    • An impact is applied at a velocity of 2000 ± 200 mm/s.

    • Specimens are examined for fractures or visible cracks.

    • The process is repeated at lower temperatures to determine the brittleness temperature.

  4. Data Analysis: The brittleness temperature is identified as the temperature at which 50% of the specimens fail under the test conditions.

Significance of Test Results

Understanding the brittleness temperature of materials helps predict their behavior in low-temperature applications. Materials with lower brittleness temperatures are more suitable for environments where they may be exposed to cold conditions, reducing the risk of sudden failure.

Applications

ASTM D746 is applicable in various industries, including:

  • Automotive: Evaluating the performance of plastic and elastomer components in cold climates.

  • Aerospace: Ensuring materials can withstand low temperatures at high altitudes.

  • Construction: Assessing the suitability of materials used in cold environments.

  • Consumer Goods: Testing products that may be exposed to low temperatures during use or storage.

Advantages

  • Standardization: Provides a consistent method for determining brittleness temperature.

  • Predictive Value: Helps in forecasting material performance in low-temperature conditions.

  • Safety Assurance: Ensures materials will not fail unexpectedly in cold environments.

Challenges

  • Specimen Preparation: Requires precise preparation to ensure accurate results.

  • Equipment Calibration: Testing equipment must be properly calibrated to maintain test integrity.

  • Environmental Control: Testing conditions must be carefully controlled to avoid skewed results.