ISO 75-2:2013

Overview

ISO 75-2:2013 - Plastics - Determination of temperature of deflection under load - Part 2: Plastics and ebonite defines test methods to determine the temperature of deflection under load for plastics (including filled and short-fibre reinforced plastics, fibre length ≤ 7.5 mm) and ebonite. It specifies three constant flexural-stress methods (designated by stress level) and the way to record the temperature at which a standard increase in deflection occurs. This part complements ISO 75-1 (general test method) and is intended for comparative material evaluation and quality control.

Key topics and requirements

• Three test methods by flexural stress
  • Method A: 1.80 MPa (preferred)
  • Method B: 0.45 MPa
  • Method C: 8.00 MPa
    Results are designated using the stress-based labels (e.g., T0.45 / T1.80 / T8.00).
• Specimen geometry and span
  • Preferred specimen: 80 ± 2 mm length × 10 ± 0.2 mm width × 4 ± 0.2 mm thickness.
  • Test span: 64 ± 1 mm.
• Standard deflection criterion
  • Standard deflection Δs is calculated from a flexural-strain increase Δε = 0.2% (see ISO 75-1 for formula).
  • Example standard-deflection values for specimen heights (h):
    • h = 3.8 mm → Δs = 0.36 mm
    • h = 4.0 mm → Δs = 0.34 mm
    • h = 4.2 mm → Δs = 0.32 mm
• Apparatus & measurement
  • Uses flexural-loading supports, heating equipment (oil, fluidized bed or air - see ISO 75-1), temperature and deflection measuring instruments and specified weights.
• Material considerations
  • Better reproducibility for amorphous plastics than semi-crystalline ones.
  • Annealing may be required to reduce moulding-condition variability; annealing typically increases the measured temperature of deflection.
• Precision & reporting
  • Precision data and heating-method effects are covered in Annex A.
  • Test reports must include method used, standard deflection, specimen details and the flexural stress designation.

Applications and users

• Practical uses:
  • Comparative evaluation of polymers for component design and service-temperature limits.
  • Quality control and material acceptance testing.
  • R&D screening when comparing materials with similar room-temperature elastic properties.
• Typical users:
  • Materials and polymer testing laboratories
  • Plastics product designers and engineers
  • Quality assurance teams and suppliers of thermoplastics, filled plastics and ebonite

Related standards

• ISO 75-1 (general test method and heating options)
• ISO 293, ISO 294-1, ISO 2818, ISO 10724-1 (specimen preparation and moulding)
• ISO 20753 (test specimen types)

Keywords: ISO 75-2:2013, temperature of deflection under load, plastics testing, ebonite, flexural stress methods, specimen dimensions, annealing, test report.