Overview
EN ISO 11357-2:2020 (ISO 11357-2:2020) specifies standardized methods for determining the glass transition temperature (Tg) and the glass transition step height (Δcp or step height) of amorphous and partially crystalline plastics using differential scanning calorimetry (DSC). Adopted by CEN as EN ISO 11357-2:2020, this third edition (2020) updates definitions and procedures to improve reproducibility of plastics testing by DSC.
Key topics and technical requirements
- Scope and principle
- Measures change in heat flow vs temperature to identify Tg and the associated change in specific heat.
- Applies to amorphous and partially crystalline polymers.
- Definitions
- Glass transition temperature (Tg): characteristic temperature of the glass transition range (method-dependent).
- Glass transition step height (Δcp(Tg)): difference between upper and lower extrapolated baselines of specific heat at Tg.
- Apparatus, specimens and calibration
- Apparatus and specimen requirements and calibration follow ISO 11357-1.
- Typical specimen and scan conditions
- Specimen mass: between 5 mg and 20 mg (use higher end for partially crystalline materials).
- Preferred scan rate: 20 K/min for heating and cooling cycles (other rates possible by agreement).
- Pre-purge: 5 min before heating.
- Thermal sequence: preliminary heating to erase thermal history (first scan), controlled cooling (~50 °C below anticipated Tg), and a second heating for measurement.
- Hold times: 5 min holds before and after cooling unless decomposition or other constraints apply.
- Final heating to about 30 K above the extrapolated end temperature.
- Data analysis methods
- Standardized methods for assigning Tg: equal-areas method, half-step-height, inflection-point.
- Step height determination from extrapolated baselines.
- Reporting and precision
- Test report content, rounding rules and precision statements are specified; calibration and whether first or second heating was used must be recorded.
- Notable revisions
- Revision of step height definition, units correction, assessment of Tg methods, stricter rules on re‑use of crucibles.
Applications and users
- Intended for:
- Polymer R&D and materials scientists characterizing thermal transitions.
- Quality control laboratories verifying Tg as a production specification.
- Contract testing labs performing DSC analysis for customers.
- Regulatory and compliance testing where consistent Tg/Δcp measurement is required.
- Practical uses:
- Evaluating polymer processing windows, service temperatures, and the fraction of amorphous content (Δcp is proportional to amorphous content in semi-crystalline polymers).
- Comparing batches, formulations, and the effects of additives or annealing on polymer mobility.
Related standards
- ISO 11357-1 - General principles for DSC of plastics (normative reference).
- ISO 472 - Plastics - Vocabulary.
- Other parts of the ISO 11357 series cover complementary DSC procedures and thermal properties.
