Overview
ISO 11357-6:2018 specifies DSC (differential scanning calorimetry) methods for measuring oxidation induction time (isothermal OIT) and oxidation induction temperature (dynamic OIT) of polymeric materials. The standard is primarily applicable to polyolefin resins-in fully stabilized or compounded form, as raw materials or finished products-but can be applied to other plastics. Tests detect the onset of exothermic oxidation by DSC to assess a material’s resistance to oxidative decomposition and the effectiveness of antioxidant systems.
Key keywords: ISO 11357-6, DSC, differential scanning calorimetry, oxidation induction time, OIT, isothermal OIT, dynamic OIT, oxidation induction temperature, polyolefin, plastics testing.
Key Topics
- Principle:
- Isothermal OIT: specimen is heated in an inert atmosphere (nitrogen) to the test temperature, then the atmosphere is switched to oxygen/air and the time to oxidation onset is recorded.
- Dynamic OIT: specimen is heated in oxygen/air at a constant heating rate; the temperature at oxidation onset is recorded.
- Test instrumentation and materials:
- DSC capable of ≥ 500 °C, with isothermal stability of ±0.3 K typical; ±0.1 K recommended for high precision.
- Use open or ventilated crucibles (aluminium preferred); crucible material can significantly influence results.
- Gas control: nitrogen, oxygen and air flows, flowmeter and gas-selector switch are required for OIT tests.
- Specimen preparation and conditioning: relevant methods for moulded/injection specimens and finished parts are referenced (e.g., ISO 293, ISO 294‑3).
- Calibration, procedure and data expression: clauses cover setting up the instrument, loading crucibles, gas flows, sensitivity adjustment, onset-detection and reporting.
- Interpretation cautions: OIT/OOT are relative measures of stabilization - they indicate antioxidant effectiveness but do not provide antioxidant concentration. Pure oxygen tests produce lower OIT/OOT than atmospheric-air tests. Surface area, temperature and heating rate affect results.
Applications
- Quality control and acceptance testing of polyolefin resins, masterbatches and finished plastic parts.
- R&D for formulation optimization and antioxidant selection.
- Failure analysis where oxidative degradation is suspected.
- Material specifications and supplier qualification in plastics manufacturing and converting.
Users: polymer testing labs, formulation scientists, quality engineers, converters, certification bodies.
Related standards
This standard provides a reproducible DSC procedure for assessing oxidative stability (OIT/OOT) and is essential for labs performing thermal analysis of plastics.
Open preview (PDF)Plastics — Differential scanning calorimetry (DSC) — Part 6: Determination of oxidation induction time (isothermal OIT) and oxidation induction temperature (dynamic OIT)