DSC Testing Oxidation Induction: ISO vs ASTM
testDSC.AdminDSC testing oxidation induction now needs a method choice. ISO/TC 61/SC 5 lists ISO 11357-6:2025 as current and ISO 11357-6:2018 as withdrawn. ASTM D3895-19 remains active for fully stabilized or compounded polyolefin resins. OIT shows relative stabilization, not a direct prediction of product lifetime.
Your request usually falls into one of two measurements: isothermal oxidation induction time or dynamic oxidation induction temperature, also called OOT. The method, gas-switch point, sample history, and report fields determine whether your results can support a useful lot-to-lot comparison.
Which OIT standard should you request now?
Request ISO 11357-6:2025 when your specification requires the current ISO method for isothermal OIT or dynamic OIT. Request ASTM D3895-19 when your quality system specifies its active polyolefin OIT procedure. Do not combine results from different methods without recording the method version and test conditions.
| Request | ISO 11357-6:2025 | ASTM D3895-19 | Use when |
|---|---|---|---|
| Isothermal OIT | Current ISO method for oxidation induction time | Active ASTM method for polyolefin OIT | You need a time-to-oxidation comparison at a fixed temperature |
| Dynamic OIT or OOT | Covers oxidation induction temperature during heating | Not the primary ASTM D3895-19 output | You need the temperature at which oxidation begins during a programmed ramp |
| Material scope | Specify the material and method conditions in your request | Section 1.1 applies to fully stabilized or compounded polyolefin resins | You are testing supplier resin before extrusion or comparing formulated lots |
| Interpretation | Use as a relative method result under stated conditions | Section 5.1 defines OIT as a qualitative stabilization assessment | You need formulation or QC evidence, not a service-life prediction |
ASTM D3895-19 Sections 1.1 and 5.1 are especially useful for purchase specifications. The standard covers fully stabilized or compounded polyolefin resins and treats OIT as a qualitative measure of stabilization. It does not establish a direct relationship between an OIT value and field lifetime.
What do isothermal OIT and dynamic OOT measure?
Isothermal oxidation induction time measures the elapsed time before oxidation begins at a selected constant temperature. Dynamic oxidation induction temperature measures the temperature at which oxidation begins during a controlled heating ramp.
An oxidation induction time DSC result is reported in minutes. A dynamic result is reported in °C. ISO 11357-6:2025 identifies both isothermal OIT and dynamic OIT, while OOT is commonly used for the dynamic oxidation-onset temperature. The two results answer different questions and should not be substituted for each other.
Use isothermal OIT when your release limit compares stabilization at a fixed temperature. Use dynamic OOT when the question is which sample begins oxidation earlier during heating. In both cases, compare only results produced with matched sample history and test conditions.
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How does dsc testing oxidation induction run?
The practical sequence is controlled heating under nitrogen, followed by an oxygen switch and detection of the exothermic oxidation onset. Intertek describes a typical sequence that heats the sample to 200 °C under nitrogen, introduces oxygen, and measures the time before the exothermic process begins.
- Load the specified polymer mass into the DSC pan. Poor sampling can misrepresent a nonhomogeneous stabilizer distribution.
- Purge and heat under nitrogen, typically to 200 °C. Volatile antioxidants may evaporate during heat-up and produce a low or misleading OIT.
- Hold at the selected temperature or continue the programmed ramp. Record the heating rate, such as 20 °C/min, for dynamic work.
- Switch from nitrogen to oxygen or air at the defined temperature and flow. Gas-switch delay or unstable flow shifts the apparent onset.
- Identify the exothermic oxidation onset and report the result in minutes or °C, with the method and calculation rule stated.
The NETZSCH example gives a useful benchmark for the scale of the measurement. Two polypropylene samples weighed 9.48 mg and 9.55 mg. They were heated to 200 °C at 20 K/min, equivalent to 20 °C/min, with a gas flow of 50 mL/min. After a 3-minute nitrogen hold, the measured OIT values were 6.6 minutes and 11.6 minutes.
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Which intake and report fields make OIT results comparable?
Comparable OIT work starts with a complete intake record. TestDSC asks for the polymer grade, stabilizer history, lot age, requested standard, target sample mass, gas-switch point, and replicate plan before the run is scheduled.
What should you provide with the sample?
- Polymer grade, formulation or compound designation, and supplier lot number
- Known antioxidant package, processing history, and stabilizer additions
- Lot age, storage conditions, and whether the material is as-received, molded, or reprocessed
- Requested standard: ISO 11357-6:2025, ASTM D3895-19, or a documented custom condition
- Target sample mass in mg, number of replicates, and acceptance or comparison criteria
- Gas-switch temperature or time, gas identity, and any required flow condition
What should the report contain?
TestDSC reports the standard and version, sample identification, measured mass, pan description, gas identity and flow, heating rate, nitrogen hold, gas-switch point, onset definition, individual replicate values, average, variability, and any deviation from the requested method. The report should also identify whether the result is isothermal OIT or dynamic OOT.
These fields help explain unexpected differences. ASTM notes that volatile antioxidants can give poor OIT results even when they perform adequately at the intended use temperature. Inconsistent gas switching and poor sampling can create similar comparison problems.
FAQ: how should you specify OIT testing?
Does a longer OIT prove longer product life?
No. ASTM D3895-19 describes OIT as a qualitative stabilization assessment. The result is an accelerated measurement under defined conditions, not a direct service-life calculation.
Should you request OIT time or OOT temperature?
Request isothermal OIT when your specification compares minutes at a fixed temperature. Request dynamic OOT when you need the oxidation induction temperature during a heating ramp.
Can results from ISO and ASTM be compared directly?
Only with caution. ISO/TC 61/SC 5 lists ISO 11357-6:2025 as current, while ASTM D3895-19 remains active. Record the method, version, sample history, gas conditions, and onset rule before comparing values. See our Frequently Asked Questions for related testing questions.
Specify your OIT method before sending samples
A useful OIT result starts with the correct standard and a complete test request. Tell TestDSC whether you need isothermal oxidation induction time or dynamic oxidation induction temperature, then provide the sample history and comparison plan. Request a method-matched quotation through our DSC oxidation induction testing service intake →
