Overview
ISO 22206:2024 - "Kraft lignin - Glass transition temperature by differential scanning calorimetry (DSC)" defines a standardized laboratory procedure to determine the glass transition temperature (Tg) of solid kraft lignins using differential scanning calorimetry (DSC). The method applies to powdered lignins isolated from kraft black liquor (acidified or carbonated isolates) and is intended to support consistent lignin characterization, quality control and material development. It does not apply to raw black liquor or lignin in the alkali form.
Key topics and technical requirements
- Scope & exclusions: Applies to solid/ powdered kraft lignin from isolation techniques (acidification, carbonation). Excludes raw black liquor and alkali-dissolved lignin.
- Apparatus: Differential scanning calorimeter (or combined DSC/TGA), inert pans and lids (pierced if hermetic), pressing tool, analytical balance (0.01 mg), drying oven (105 ± 2 °C), desiccator and inert purge gas (O2 ≤ 0.001% v/v; H2O ≤ 0.001% w/w).
- Sampling & sample prep: Homogenize and sieve to 200-mesh; dry test sample (1–3 g) to constant mass at 105 °C; store samples in desiccator.
- Test specimen: 3–10 mg placed in pan (thin layer for good heat transfer); seal lids with pressing tool.
- Analysis cycles: Include a cleaning cycle, a pre-cycle (heating and cooling under inert gas) and a core cycle. Heating/cooling rates specified at 10 °C/min. Core cycle end temperature is based on decomposition onset (Td2% − 5 °C); if Tg > 180 °C, repeat with final ramp to Tg + 40 °C.
- Evaluation & reporting:
- Tg reported as the instrument-provided inflection point; if unavailable, use mid-point of the transition.
- If multiple inflections occur, report the highest temperature inflection.
- Perform at least three replicate specimens; report mean Tg and standard deviation (temperatures to nearest integer).
- Test report must reference ISO 22206:2024 and include instrument details, calibration, sample ID, specimen mass, date/place, and any deviations.
Applications and users
ISO 22206:2024 is valuable for:
- Lignin producers and pulp mills seeking product specification and quality control.
- Materials scientists, polymer formulators and R&D teams evaluating lignin for thermoplastics, resins, carbon fibers, adhesives and composite applications.
- Analytical laboratories performing thermal characterization and interlaboratory comparisons.
Standardized Tg measurement helps determine processing windows, drying behavior, softening points and potential crosslinking in lignin-derived materials.
Related standards
Keywords: ISO 22206:2024, kraft lignin, glass transition temperature, Tg, differential scanning calorimetry, DSC, lignin characterization, thermal properties, black liquor.