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