Overview
ISO 11357-5:2025 - Plastics - Differential scanning calorimetry (DSC) - Part 5 specifies a standardized method for determining characteristic reaction-curve temperatures and times, enthalpy of reaction, and degree of conversion using conventional DSC. The standard applies to monomers, prepolymers and polymers (solid or liquid) and materials that may contain fillers and/or initiators. This edition is limited to conventional DSC and excludes fast DSC (see ISO 23976).
Key topics and requirements
- Scope and limits
- Applicable to conventional DSC only; not for fast DSC when reactions overlap decomposition.
- Warning for materials that can give runaway or hazardous reactions.
- Methods
- Temperature-scanning method: perform scans (recommended 5 K/min to 20 K/min) from ambient to a temperature that fully captures the reaction peak but below decomposition onset.
- Isothermal method: two options - constant-temperature procedure or start-at-ambient then rapidly heat to measurement temperature. Record times to reaction onset and characteristic times from thermal equilibrium.
- Specimen and instrumentation
- Typical specimen mass: 5 mg to 20 mg, adjusted for signal strength.
- Use gas-tight crucibles for specimens releasing volatiles.
- Calibration, apparatus and specimen conditioning as per ISO 11357-1.
- Data and calculations
- Define characteristic temperatures (onset, extrapolated onset, peak Tmax, extrapolated end, end) from DSC curves.
- Enthalpy of reaction (ΔHr): integrate area between peak and interpolated baseline.
- Degree of conversion (α): calculated from temperature-scan or isothermal curves; account for residual enthalpy by post-isothermal scan.
- Quality and reporting
- Precision and reporting requirements are specified; include test conditions, scan rate, specimen mass and any conditioning.
Applications and who uses it
ISO 11357-5:2025 is practical for:
- Polymer R&D and formulation development (polymerization, crosslinking studies)
- Quality control in plastics manufacturing (reaction completeness, curing verification)
- Materials characterization labs and third-party testing services
- Regulatory and safety assessments where thermal reaction behavior and conversion are critical
Keywords: ISO 11357-5:2025, differential scanning calorimetry (DSC), plastics testing, enthalpy of reaction, degree of conversion, polymerization, crosslinking, isothermal DSC, temperature-scan.
Related standards
- ISO 11357-1 - General principles, apparatus and calibration for DSC (normative reference).
- ISO 23976 - Fast DSC - referenced for cases where high heating rates are needed to separate reaction and decomposition effects.