Sustainable Testing of Paint and Coatings

Significance of the Topic

The global paint and coatings industry is experiencing robust growth driven by demand for protective, decorative, and functional coatings. As formulations become increasingly complex, traditional wet chemical methods struggle to meet rising throughput, safety, and environmental requirements. Visible–near-infrared (Vis-NIR) spectroscopy addresses these challenges by offering rapid, nondestructive, and reagent-free analysis suitable for multiple production stages.

Objectives and Overview of the Study

This white paper demonstrates how Vis-NIR spectroscopy can streamline quality control across raw material verification, formulation, production, and final product testing in paint and coatings manufacturing. It presents applications covering pigment concentration, dye quantification, additive analysis (paint driers), binder evaluation (amine content), and solvent/cosolvent measurement. The goal is to highlight economic and ecological advantages over conventional methods.

Methodology and Applied Instrumentation

Analyses were performed using a bench-top Vis-NIR spectrometer operating over the 400–2 500 nm range. Chemometric calibration models based on partial least squares regression correlated spectral data with reference values from standard ASTM methods. Measurement modes included inline, online, at-line, and offline sampling. No sample preparation or reagents were required, and each scan typically completed in under one minute.

Main Results and Discussion

• Dye Content in Inks: Ball-pen ink samples (dye 0.56–4.56 %) yielded a calibration R² of 0.99 and validation error < 0.1 % versus titration.
• Paint Driers: Five cobalt octoate formulations were differentiated by their spectral fingerprints. Specific gravity and dynamic viscosity predictions correlated strongly with ASTM D1289-85 (R² > 0.98).
• Amine Number in Dipping Paints: Free amine concentrations (33.8–48.3 mmol/kg) in electrodeposition paints achieved R² = 0.97 against titration.
• Cosolvents in Water-Based Paints: Butyl glycol and propylheptyl alcohol predictions showed validation errors below 1 % relative to chromatography results.

Benefits and Practical Applications of the Method

• High Throughput: Multiple parameters in a single, sub-minute measurement.
• Reagent-Free and Nondestructive: No sample alteration and reduced waste disposal costs.
• Operational Safety: Eliminates handling of hazardous chemicals and simplifies staff training.
• Flexibility: Applicable to solids, liquids, powders, and complex matrices at various process points.

Future Trends and Opportunities

Advances in miniaturized and fiber-optic Vis-NIR probes will enable real-time inline monitoring of coating processes. Integration with machine learning and Industry 4.0 platforms can enhance predictive maintenance and formulation optimization. Expansion into new regulatory environments and low-VOC formulations will further drive adoption.

Conclusion

Vis-NIR spectroscopy offers a sustainable, cost-effective alternative to traditional wet chemical analyses in the paint and coatings industry. Its ability to deliver rapid, accurate, and multi-parameter data supports efficient quality control from raw materials through final products, aligning with ecological and safety goals.

References

1. Detiveaux S., Bangert C. The State of the Global Coatings Industry. Products Finishing, 2016.
2. IHS Markit. Paint and Coatings Industry Overview. Chemical Economics Handbook, 2016.
3. Koleske J. Paint and Coating Testing Manual. ASTM International, 2012.
4. Metrohm Application Note AN-NIR-026: Dye Determination in Inks, 2016.
5. Gupta A. Optimal Quantities of Driers in Paint Formulation. Int. J. Eng. Sci. Technol., 2013.
6. Metrohm Application Note AN-NIR-033: Paint Drier Analysis, 2016.
7. Metrohm Application Note AN-NIR-030: Amine Number in Dipping Paints, 2016.
8. Stoye D., Freitag W. Paints, Coatings, and Solvents. Wiley-VCH, 1998.
9. Metrohm Application Note AN-NIR-029: Cosolvent Content in Water-Based Paints, 2016.