ISO 11358-2:2021

Overview

ISO 11358-2:2021 - "Plastics - Thermogravimetry (TG) of polymers - Part 2: Determination of activation energy" specifies a standardized thermogravimetric (TG) method to determine the activation energy (Ea) for polymer decomposition using thermogravimetric analysis (TGA). The method uses multiple dynamic heating-rate TG runs to derive Ea from the temperature dependence of decomposition according to the Arrhenius relationship. It applies only when the decomposition proceeds by a single mechanism or by clearly separated single-stage steps in a multistage reaction.

Key Topics

• Principle: heating specimens at several heating rates, measuring mass change vs temperature, selecting temperatures at given degrees of conversion (C), and calculating Ea from the slope of log(heating rate) vs 1/T plots using the Ozawa / Flynn–Wall approximation.
• Test conditions and apparatus: refers to ISO 11358-1 for general TG principles, apparatus requirements, and calibration (mass and temperature).
• Specimen preparation: powders, pellets, flakes, filaments or film; small particle size preferred (grinding in liquid-nitrogen mill acceptable).
• Experimental parameters:
  • Use three or more heating rates; lowest and highest heating rates must differ by a factor ≥ 5.
  • Preferred specimen mass < 10 mg and heating rates < 20 K·min⁻¹ to avoid temperature lag.
  • Correct for buoyancy and empty-crucible mass changes by subtracting blank runs at each heating rate.
• Atmosphere control: inert (e.g., N2) for non-oxidative tests or oxidative gas (air/O2) for oxidation studies; gas purity and water content per ISO 11358-1.
• Data presentation: TG curves (mass or % mass vs temperature) and graphical determination of temperatures corresponding to fixed degrees of conversion.
• Limitations and notes:
  • Not suitable for very high degrees of conversion.
  • Unreliable if Ea varies widely with conversion or if log β vs 1/T is non-linear.
• Reporting: detailed test report requirements (sample ID, mass, crucible, atmosphere, heating rates, calibration standards, activation energy value, observations, date).

Applications

• Determining thermal stability and decomposition kinetics of polymers and polymer formulations.
• Material R&D: comparing additives, stabilizers, fillers, and recycling/degradation behavior.
• Quality control and batch comparison in polymer manufacturing.
• Failure analysis and lifetime prediction based on kinetic parameters.
• Thermal analysis laboratories, polymer scientists, instrument manufacturers, and regulatory or certification bodies performing standardized TGA kinetic evaluations.

Related Standards

• ISO 11358-1 - Plastics - Thermogravimetry (TG) of polymers - Part 1: General principles (apparatus, calibration, terminology).
• ISO 11358-3 - referenced in edition changes (alignment of conversion/rate terminology).

Keywords: ISO 11358-2:2021, thermogravimetry, TG, thermogravimetric analysis, activation energy, Arrhenius, polymer decomposition, Flynn–Wall, Ozawa, thermal stability, TGA.