Butyl glycol and propylheptyl alcohol in water-borne paint

Significance of the topic

The control of additive content such as butyl glycol and propylheptyl alcohol is critical for consistent performance and quality in water-based paints. Traditional laboratory methods are often time-consuming and resource-intensive. Vis-NIR spectroscopy offers a rapid, non-destructive alternative capable of delivering multi-component analysis in a single measurement.

Study objectives and overview

This study aimed to develop and validate quantitative models using visible-near-infrared (Vis-NIR) spectroscopy to determine concentrations of butyl glycol and propylheptyl alcohol in light gray and black water-borne paint formulations. The objective was to replace conventional lab assays with a faster, user-friendly spectroscopic method suitable for routine quality control.

Used instrumentation

• NIRS XDS SmartProbe Analyzer (Metrohm code 29211610) equipped with a transflection probe
• Vision Software 4.0.3 (Metrohm code 66069102) for chemometric model development

Methodology

• Samples: Light gray and black paint formulations spiked with varying levels of butyl glycol (0.80–1.15 %) and propylheptyl alcohol (0.90–1.35 %).
• Measurement: Transflection mode over 400–2500 nm with continuous stirring to maintain homogeneity.
• Spectral pretreatment: First derivative, segment size 20 nm, gap size 1 nm.
• Chemometrics: Partial Least Squares regression, external validation on independent samples.

Main results and discussion

• Butyl glycol in black paint: PLS model (2 factors), wavelength 500–1080 nm and 1120–1950 nm, R² = 0.9904, SEC = 0.0093 %, SEV = 0.0095 %.
• Butyl glycol in light gray paint: PLS model (2 factors), wavelength 1120–1950 nm, R² = 0.9732, SEC = 0.0216 %, SEV = 0.0882 %.
• Propylheptyl alcohol in black paint: PLS model (3 factors), wavelength 500–1080 nm and 1120–1950 nm, R² = 0.9957, SEC = 0.0068 %, SEV = 0.0969 %.
• Propylheptyl alcohol in light gray paint: PLS model (2 factors), wavelength 1120–1950 nm, R² = 0.9975, SEC = 0.0072 %, SEV = 0.0704 %.
• External validation residuals remained within ±0.07 %, confirming model accuracy and robustness.

Benefits and practical applications

Vis-NIR spectroscopy enables rapid (< 1 minute per sample), reagent-free analysis of multiple additives in paint formulations. The approach reduces sample preparation and operator training, supporting real-time quality control in production environments.

Future trends and potential applications

• Expansion to additional additives and complex paint matrices.
• Integration of on-line process monitoring in paint manufacturing plants.
• Development of portable, handheld Vis-NIR systems for field testing.
• Application of advanced machine learning algorithms for improved model transferability.

Conclusion

The Vis-NIR method successfully quantified butyl glycol and propylheptyl alcohol in water-borne paints with high accuracy and precision. Its speed, versatility, and ease of use make it a valuable tool for routine quality assurance and process optimization in the paint industry.