Overview
ISO 11358-3:2021 - Plastics - Thermogravimetry (TG) of polymers - Part 3 specifies a standardized analysis method for determining the activation energy of polymer decomposition using the Ozawa‑Friedman plot and for preparing master plots (master curves) to verify reaction kinetics obtained from thermogravimetric analysis (TGA/TG). The standard applies to TG data obtained under different temperature profiles (isothermal, constant heating rate, sample‑controlled thermal analysis, temperature jump, repeated scanning) and gives requirements for specimen preparation, calibration, data presentation and kinetic verification.
Key topics and requirements
- Activation energy determination: Uses the Ozawa‑Friedman method - plot of ln(rate of conversion) versus reciprocal absolute temperature (1/T); slope yields activation energy (–Ea/R).
- Rate of conversion (dC/dt): Measurement and calculation of conversion rate at fixed conversion levels are required for the Ozawa‑Friedman analysis.
- Master curves / master plots: Preparation of conversion vs generalized time or generalized rate plots to verify kinetic models and reaction mechanisms (g(α), f(α)).
- Test conditions:
- Typical specimen mass: 1 mg to 10 mg.
- Recommended linear heating rates: 2 K·min⁻¹ to 10 K·min⁻¹.
- Use of CRTG (sample mass controlled rate thermogravimetry), LHTG (linear heating rate TG), and isothermal TG data.
- Atmospheres: Differentiates non‑oxidative and oxidative reaction procedures - atmospheres specified by ISO 11358‑2.
- Apparatus and calibration: References ISO 11358‑1 for TG apparatus requirements and mass/temperature calibration procedures.
- Reporting and precision: Graphical presentation (Ozawa‑Friedman plots), tabulated activation energies at different conversion levels, and test report content are specified; mathematical background included in an informative annex.
Practical applications
- Characterizing thermal stability and decomposition kinetics of polymers and additives.
- Comparing activation energies to evaluate flame retardants, stabilizers or recycling feedstock behavior.
- Supporting lifetime prediction, accelerated aging studies and process design (e.g., extrusion, thermal processing).
- Validating kinetic models used in simulation of decomposition or combustion in R&D and failure analysis.
Who uses this standard
- Polymer scientists and thermal analysis laboratories performing thermogravimetry (TG/TGA).
- R&D teams in plastics, composites, coatings and additive manufacturers.
- Quality assurance, regulatory compliance, and materials selection engineers assessing thermal performance.
- Academic researchers studying polymer reaction kinetics and degradation mechanisms.
Related standards
- ISO 11358‑1 - TG apparatus, general principles, calibration.
- ISO 11358‑2 - Determination of activation energy; gas atmosphere specifications for oxidative/non‑oxidative tests.
Keywords: ISO 11358-3, thermogravimetry, Ozawa-Friedman plot, activation energy, polymer kinetics, TGA, master curves, CRTG, LHTG.
Open preview (PDF)Plastics — Thermogravimetry (TG) of polymers — Part 3: Determination of the activation energy using the Ozawa-Friedman plot and analysis of the reaction kinetics