FTIR Analysis of Glues for Quality Control and Development

Significance of the topic

Adhesives are essential across industries—from automotive lightweight assemblies to medical wound closure—demanding rigorous quality control and tailored performance. Fourier transform infrared (FTIR) spectroscopy offers rapid, non-destructive chemical analysis of both raw materials and finished adhesive products to ensure consistency and drive innovation.

Objectives and study overview

This application note demonstrates how Bruker’s ALPHA II FTIR spectrometer and LUMOS II FTIR microscope, in combination with OPUS software, address key analytical tasks: incoming goods inspection, quality control, reaction monitoring, reverse engineering of competitive formulations, and failure analysis of microscopic defects.

Methodology and instrumentation

FTIR analysis was performed without sample preparation using attenuated total reflection (ATR) modules for bulk measurement and a microscope for spatially resolved studies. Key components:

• ALPHA II FTIR spectrometer with interchangeable ATR modules
• LUMOS II FTIR microscope with motorized polarizers
• OPUS spectroscopy software featuring quick compare, reaction monitoring, spectrum search, and mixture analysis

Main results and discussion

Incoming goods inspection: A reference spectrum of an amine hardener was compared to a batch sample via correlation analysis, achieving >99% match and enabling automatic pass/fail evaluation.

Reaction monitoring: Time-resolved ATR measurements captured curing of a plastic adhesive (butyl acetate, acetone, PMMA), revealing solvent evaporation kinetics and polymer concentration changes through band integrations at 1040 and 1144 cm–1.

Reverse engineering: Mixture analysis of an unknown multi-purpose glue identified water and acrylate polymers as main components; reconstructed composite spectrum matched the query within minimal deviation.

Failure analysis: Microscopic defects in a PET-adhesive layer were located by automated grid mapping (25×25 μm apertures) and chemical imaging. Spectra of needle-like crystals showed a distinct band at 1680 cm–1 and an N–H signal at 3267 cm–1, indicating a nitrogen-containing contaminant, which was ruled out as a suspected amide based on spectral mismatch.

Benefits and practical applications of the method

FTIR spectroscopy with ATR and microscopy enables:

• Fast, reagent-free identity checks of raw materials
• Quantitative monitoring of curing and reaction kinetics
• Non-destructive spatial mapping of defects at micrometer resolution
• Efficient reverse engineering and product development support

Future trends and potential applications

Emerging directions include integration of multivariate and machine-learning algorithms for automated spectrum interpretation, inline process monitoring in production environments, enhanced imaging capabilities for sub-micron analysis, and expansion of reference libraries for broader material coverage.

Conclusion

Combining the ALPHA II spectrometer and LUMOS II microscope with OPUS software delivers a versatile FTIR platform for comprehensive adhesive analysis—from raw-material verification and cure monitoring to defect identification and reverse engineering—supporting quality assurance and innovation in industrial and medical applications.

References

No references were cited in the original document.