ISO 11357-5 2025: DSC Conversion Reporting
testDSC.AdminISO 11357-5 2025 changes the buyer question from a peak temperature to a calculated conversion result. A defensible report states α as a dimensionless degree of conversion at a stated temperature and/or time, then shows sample mass, heating rate, atmosphere, flow, reaction enthalpy, residual enthalpy, and the calculation route.
The 2025 edition separates reaction-curve measurement from interpretation of conversion. It also draws attention to decomposition overlap. This guide turns those changes into a report checklist for R&D, formulation, and QC decisions.
What does ISO 11357-5 2025 change in practice?
ISO 11357-5 2025 is the third edition and replaces ISO 11357-5:2013. The English preview limits Clause 1 to conventional DSC, excludes fast DSC covered by ISO 23976, and warns that reaction heat can overlap with decomposition.
The ISO 11357-5:2025 — Differential scanning calorimetry listing establishes the revised edition. The Swedish Institute for Standards entry for SS-EN ISO 11357-5:2025 provides a national adoption listing of the same edition. Neither fact turns a peak into a conversion result.
A peak temperature identifies where heat flow reaches a maximum under a specific program. It does not state how much material reacted. A compliant report must connect reaction temperature, time, enthalpy, and calculated α.
See also: DSC Testing for Aerospace Materials: Ensuring Safety and Performance
What must a DSC degree of conversion report show?
A DSC degree of conversion report must show α as a dimensionless value at a stated temperature and/or time. The report must also identify the measured conditions and explain how the value was calculated.
The English preview places degree-of-conversion calculation in Clause 10.3 and test reporting in Clause 12. For baseline terminology, use our differential scanning calorimetry dsc analysis reference, but do not accept a report that stops at a curve label.
What to demand in the result line
| Report field | Minimum demand | Decision or use when |
|---|---|---|
| Degree of conversion | α as a dimensionless value at a stated °C and/or time in min | Use when judging reaction progress rather than peak position |
| Sample and program | Sample mass in mg and heating rate in °C/min | Use when comparing runs or repeating the method |
| Atmosphere | Gas identity and flow in mL/min | Use when oxygen exposure could change the reaction |
| Reaction heat | Reaction enthalpy in J/g | Use when comparing formulation or batch behavior |
| Residual heat | Residual enthalpy after the reported reaction step | Use when checking whether unreacted material remains |
| Calculation route | Integration limits, baseline treatment, and equation or balance used | Use when auditing or reproducing α |
Require one real anonymized TestDSC conversion result in the report. That result must show the measured α, its stated temperature and/or time, sample mass in mg, heating rate in °C/min, atmosphere and flow in mL/min, reaction enthalpy in J/g, residual enthalpy, and the calculation route. A schematic curve is not a substitute.
Use the existing TestDSC example only as a method-record model: 7.84 mg, nitrogen at 50 mL/min, −30 °C to +180 °C, and 10 °C/min, with duplicate Tg values of 74.6 °C and 74.9 °C. Those figures demonstrate traceable setup. They are not a conversion result.
If you need a repeatable method record before conversion analysis, review DSC Experiment Setup: A Beginner’s Guide to Running Your First Test.
See also: Exothermic and Endothermic Reactions in DSC: What the Peaks Tell You
Which test route fits your reaction?
Temperature scanning under Clause 9.2 follows heat flow as temperature rises. Isothermal testing under Clause 9.3 follows heat flow over time at a fixed temperature. Choose the route that matches the variable you need to control; do not convert a scan peak directly into α.
| Route | What the DSC reaction curve provides | Use when | Main caution |
|---|---|---|---|
| Temperature scanning | Reaction onset, peak, end, and heat over a programmed temperature range | You need reaction temperatures or a screening comparison | Heating rate shifts the observed curve and does not itself prove conversion |
| Isothermal testing | Heat flow and conversion behavior against time at a selected temperature | You need time-dependent reaction progress at process temperature | The selected temperature must be stated with the time basis |
| Paired testing | Temperature landmarks plus time-dependent conversion evidence | A scan alone cannot separate process behavior from conversion | Both datasets need linked baselines and calculation routes |
When heating rate changes peak location, use DSC Heating Rate Effect: Compare Peaks to frame the comparison correctly. If crystallization or cooling changes the baseline, the neighboring dsc analyse guidance is the relevant next check.
When does decomposition invalidate the result?
Decomposition invalidates a conversion result when the measured exotherm includes decomposition heat that cannot be separated from the intended reaction. The trigger is usually an overlapping exotherm, a distorted reaction curve, or a runaway reaction during the scan.
The English preview of ISO 11357-5 2025 specifically warns about reactions that overlap with decomposition. Report the limitation instead of presenting the combined area as a clean DSC degree of conversion.
- Confirm the method scope and route. Failure mode: a fast DSC dataset is reported as conventional DSC without addressing ISO 23976.
- Inspect the raw DSC reaction curve and baseline. Failure mode: an overlapping exotherm makes one integrated area look like a single reaction.
- Check for runaway behavior, abrupt heat-flow escalation, or an unexplained second event. Failure mode: decomposition is counted as reaction heat.
- Verify α against the stated temperature and/or time. Failure mode: a peak temperature is labeled as conversion.
- Check mass, heating rate, atmosphere, flow, reaction enthalpy, residual enthalpy, and calculation route. Failure mode: the result cannot be reproduced or compared.
- Require a real anonymized conversion result before approval. Failure mode: a polished graph hides the absence of a measured dimensionless α.
FAQ: ISO 11357-5 2025
Is a peak temperature a DSC degree of conversion?
No. A peak temperature is a characteristic point on a heat-flow curve. Conversion requires α, a stated temperature and/or time, and a disclosed calculation route.
Does ISO 11357-5 2025 cover fast DSC?
No. The English preview identifies conventional DSC in Clause 1 and excludes fast DSC under ISO 23976.
Can a decomposition-overlapped scan report conversion?
Only with a clear limitation if the reaction and decomposition cannot be separated. Do not report the combined exotherm as a clean conversion value.
What should you send with a DSC test request?
Send the sample identity, expected temperature range, atmosphere preference, reaction question, and any known decomposition risk. The TestDSC DSC Analysis Lab: Pre-Ship Test Request Checklist helps capture the method details before testing.
Conclusion: Specify the result, not only the peak
ISO 11357-5 2025 gives you a stronger basis for reviewing reaction data. Ask for α at a stated temperature and/or time, reaction and residual enthalpy, complete test conditions, and a calculation route that does not hide decomposition. For customer-supplied samples, use TestDSC DSC thermal analysis and viscosity testing services when your decision depends on traceable heat-flow data →
