Thermogravimetry (TG) of Cellulose Nanofibers

Importance of the topic

Cellulose nanofibers (CNF) represent a renewable, lightweight and high-strength material derived from plant cellulose. Their carbon-neutral origin and remarkable mechanical properties make them attractive for sustainable applications, including automotive components and composite materials. However, understanding their thermal stability is critical to ensuring performance and durability in end-use environments.

Study objectives and overview

This work evaluates the thermal stability of six CNF variants using thermogravimetric analysis (TGA). The materials include three pulp-derived CNFs (BiNFi-s standard, extra-long and extra-short fiber lengths) and three non-pulp-derived types (TEMPO-oxidized CNF, nano-fibrillated bacterial cellulose (NFBC) and carboxymethylcellulose (CMC)). The goal is to characterize decomposition behavior, quantify weight-loss stages and compare onset temperatures across samples.

Methodology and Instrumentation

Samples were initially dried at 80 °C for 8 hours and then subjected to additional drying at 80 °C for 2 hours to remove residual moisture. A thermogravimetric analyzer equipped with a 5 mm height macrocell and a perforated drop lid for gas ventilation was used. Heating was performed under a controlled atmosphere while recording mass change as a function of temperature up to 300 °C.

Main results and discussion

All CNF samples exhibited an initial weight loss below 200 °C attributed to moisture evaporation. Decomposition of the cellulose backbone commenced above 250 °C. Key observations include:

• Pulp-derived CNFs displayed a fiber-length effect: the 5% mass loss temperature increased from 285 °C (standard) to 312 °C (extra-short), indicating that shorter fibers confer higher thermal stability.
• Comparison with 97% pure cellulose powder showed a two-stage decomposition for CNF: a first stage around 140 °C linked to non-cellulosic residues and a second stage around 260 °C overlapping with pure cellulose decomposition.
• TEMPO-oxidized CNF and NFBC samples discolored during initial drying, suggesting early thermal degradation. Vacuum-dried TEMPO CNF exhibited a higher decomposition onset (222 °C) than conventionally dried material (182 °C).
• CMC underwent two-stage weight loss with a lower 5% mass loss temperature (243 °C) compared to cellulose powder (303 °C), reflecting its modified chemical structure.

Benefits and practical applications

TGA provides a rapid and sensitive technique for assessing CNF thermal stability, guiding material selection and processing parameters for industrial applications. Understanding decomposition profiles supports the design of heat-resistant composites for automotive, packaging and electronic industries.

Future trends and potential applications

Advancements may include coupling TGA with evolved gas analysis (FTIR or MS) to identify volatile degradation products, and exploring chemical or surface modifications to enhance CNF thermal resistance. Integration of CNF in high-temperature composites and additive manufacturing materials represents a promising area of development.

Conclusion

Thermogravimetric analysis has elucidated the thermal decomposition behavior of diverse CNF types. Variations in fiber length and chemical modification significantly influence thermal stability. These insights are essential for optimizing CNF-based materials in applications where heat exposure is critical.

References

• Application News No. S30: Observation of Cellulose Nanofibers and Measurement of Fiber Length/Width, Shimadzu Corporation
• Application News No. Q121: Characterization of Fiber Length and Dispersibility of Cellulose Nanofibers, Shimadzu Corporation