Measurement of Degree of Crystallinity of Cellulose Nanofiber

Significance of Topic

Cellulose nanofiber (CNF) is a plant-derived nanomaterial with exceptional mechanical strength, low weight and functional properties such as gas barrier performance, transparency and absorption. Its renewable origin and low environmental footprint make it a promising candidate for automotive, electronic and packaging applications. Understanding and controlling its crystalline structure is vital for optimizing performance and durability.

Objectives and Overview

This study demonstrates the use of X-ray diffraction (XRD) to evaluate the degree of crystallinity in commercially available aqueous dispersions of CNF. Five samples (A–E) with varying fiber lengths were analyzed to compare their crystalline content and assess the suitability of the Segal method for CNF quality control.

Methodology and Instrumentation

The analysis comprised several steps:

• Sample Pretreatment: Dilute each dispersion tenfold, homogenize by stirring, then form thin sheets via suction filtration. Dry sheets under pressure between plates to prevent warping.
• XRD Measurement: Shimadzu XRD-7000 diffractometer with horizontal goniometer and zero-background sample holder. Parameters:
  • X-ray source: Cu target, 40 kV, 40 mA
  • Monochromator: Counter monochromator
  • Scan range: 2θ 10°–32.5° at 2°/min
  • Detector: Scintillation detector
  • Mode: Continuous scan
• Crystallinity Calculation: Segal method (1959) using Ci = (I002 − Iam) / I002 × 100, where I002 is the intensity of the 002 crystalline peak and Iam the intensity at the amorphous valley.

Main Results and Discussion

• XRD Patterns: All CNF samples showed distinct crystalline peaks at around 2θ 16° and 22° superimposed on an amorphous halo, indicating a mixed crystalline–amorphous structure.
• Crystallinity Values: Calculated Ci values ranged from 76 % to 86 %:
  • Sample A: 84 %
  • Sample B: 86 %
  • Sample C: 76 %
  • Sample D: 77 %
  • Sample E: 82 %
• Fiber Length Influence: Variations in crystallinity reflect differences in fiber morphology and processing history, highlighting the impact of fiber length on crystalline ordering.

Benefits and Practical Applications

XRD-based crystallinity analysis offers:

• Rapid, non-destructive assessment of CNF structural properties.
• Quantitative comparison of production batches for quality control.
• Insight into the relationship between crystalline structure and material performance to guide processing and application development.

Future Trends and Opportunities

• Advanced XRD techniques (e.g., in situ measurements, synchrotron sources) to monitor structural evolution during processing.
• Machine learning models to predict crystallinity from raw diffraction data and automate quality assessments.
• Extension of analysis to CNF composites and chemically modified fibers for tailored functional materials.

Conclusion

X-ray diffraction combined with the Segal method enables reliable determination of cellulose nanofiber crystallinity. This approach supports robust quality control and material optimization for emerging CNF applications, while advanced instrumentation and data analytics promise further enhancements.

References

• No explicit literature list was provided in the original document.