Shimadzu FTIR talk letter vol. 36

Innovations in Conductive Polymer Composites and FTIR Spectroscopy Applications

Significance of the topic
Lightweight carbon fiber–reinforced plastics (CFRP) demand integrated multifunctional capabilities, such as lightning protection, while rapid, reliable identification of plastic materials is essential for recycling and environmental monitoring. Advanced conductive polymer matrices and Fourier transform infrared (FTIR) spectroscopy together address aerospace safety, cost reduction, and plastic waste challenges.
Aims and overview of the study

• Develop intrinsically conductive polymer matrices based on polyaniline (PANI) for CFRP lightning protection to replace heavy metal meshes.
• Explain FTIR interferometer principles, interferogram sampling, and dynamic alignment techniques for high-precision spectral acquisition.
• Demonstrate FTIR-based methods for rapid identification of plastics—including biomass-derived, biodegradable, UV-degraded, and heat-damaged materials.

Methodology and Instrumentation

• Preparation of PANI/DBSA/DVB complexes via controlled thermal doping and shear mixing; thermal curing produces conductive polymer matrices evaluated under simulated lightning strikes.
• Shimadzu FT-IR IRAffinity-1S with ATR spectroscopy and Michelson interferometer employing a He–Ne laser for path-difference sampling and dynamic alignment to maintain mirror tilt within 0.5 arcsec.
• Plastic Analyzer system: IRSpirit FTIR, QATR-S single-reflection ATR, IRTracer-100 with AIM-9000 infrared microscope, and specialized method package including UV- and thermal-damaged plastics libraries and macro programs for streamlined analysis.

Main results and discussion

• CFRP panels with conductive polymer matrices endured lightning-strike tests with minimal damage, indicating potential to eliminate heavy metal protection layers and reduce weight and cost.
• Dynamic alignment in the Michelson interferometer ensured reproducible interferograms by matching stationary mirror tilt to that of the moving mirror, minimizing sampling errors at 314 nm intervals.
• Single-reflection ATR and micro-ATR microscopy distinguished conventional polyethylene from biomass-based PE, biodegradable PHBH straw from polypropylene, and identified UV- or heat-degraded plastics by referencing dedicated spectral libraries.

Benefits and practical applications

• Integrated lightning protection within CFRP reduces structural weight, manufacturing complexity, and galvanic corrosion risk in aerospace components.
• High-throughput FTIR plastic analysis supports quality control, sorting in recycling streams, and microplastic identification in environmental samples.
• Proprietary UV- and thermal-damage libraries enable accurate identification of aged or degraded plastics, enhancing failure analysis and contamination monitoring.

Future trends and potential uses

• Optimization of mechanical performance and manufacturability of conductive polymer–based CFRP for broader structural applications.
• Adoption of semiconductor laser interferometers for compact, robust FTIR systems with improved wavelength stability.
• Expansion of specialized spectral libraries to cover emerging polymer chemistries, environmental aging processes, and additive screening.

Conclusion
Conductive polymer matrices in CFRP and advances in FTIR interferometry collectively offer multifunctional, lightweight structural solutions and powerful analytical tools for material identification, addressing both aerospace safety and sustainable plastic management.
References

• [1] V. Kumar et al., Journal of Reinforced Plastics and Composites 34, 1298 (2015).
• [2] T. Yokozeki et al., Composites Science and Technology 117, 277 (2015).
• [3] V. Kumar et al., Polymer 149, 169–177 (2018).
• [4] Y. Zhou et al., Polymer 202, 122723 (2020).