ISO 812:2017

Overview

ISO 812:2017 specifies a standardized method for determining the low-temperature brittleness of vulcanized or thermoplastic rubber. The standard defines the lowest temperature at which rubber test pieces do not fracture under a specified impact and the temperature at which 50% of test pieces fail under the same conditions. ISO 812 is intended for predicting rubber behavior in low-temperature applications when deformation and impact conditions are similar to the test method.

Key Topics and Requirements

• Three test procedures
  • Procedure A - determination of the brittleness temperature (lowest non-failing temperature).
  • Procedure B - determination of the 50% brittleness temperature (temperature giving half failure rate).
  • Procedure C - impact at a specified temperature (used for classification and specification).
• Definitions
  • Brittleness temperature, 50% brittleness temperature, testing speed, and failure (visible crack, fissure, hole, or complete separation).
• Apparatus and test conditions
  • Impact speed: 2.0 m/s ± 0.2 m/s at impact; striking energy normally ≥ 3.0 J per test piece.
  • Striker geometry and clearances are specified (e.g., striking edge radius ~1.6 mm).
  • Test-piece types and dimensions (type A strip: 26–40 mm long, 6 mm ±1 mm wide, 2.0 mm ±0.2 mm thick; type B shape provided).
  • Heat-transfer medium requirements (liquids or gases that remain fluid and are chemically inert at test temperatures); examples range from silicone fluids to methylcyclohexane cooled with liquid nitrogen for very low temperatures.
• Test procedure details
  • Conditioning times (e.g., 5 min in liquid medium), immersion depth, clamping torque guidance, and stepwise temperature sequences (10 °C gross steps then 2 °C refinement).
  • Calculation or graphical methods for 50% brittleness temperature.
• Calibration and precision
  • Equipment calibration schedule (Annex B) and speed calibration methods (Annex A).
  • Limitations: results depend on impact rate and test conditions and may not equal the lowest usable service temperature.

Applications and Who Uses It

• Quality control and acceptance testing for manufacturers of vulcanized rubber and thermoplastic rubber products (seals, hoses, gaskets, automotive components, cold‑climate elastomers).
• Material selection and specification by engineers and procurement specialists to ensure rubber parts resist low-temperature embrittlement under specified impact conditions.
• Test laboratories performing standardized rubber testing and certification.
• Research and development teams evaluating formulations, plasticizer effects, or crystallization behavior at low temperatures.

Related Standards

• ISO 4646 - similar test for rubber-coated fabrics.
• ISO 23529 - preparing and conditioning test pieces for physical test methods.
• ISO 18899 - guide to calibration of test equipment.

Keywords: ISO 812, low-temperature brittleness, rubber testing, brittleness temperature, 50% brittleness temperature, vulcanized rubber, thermoplastic rubber, impact tester, test pieces.